Long-term memory

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Long-term_memory 

Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to sensory memory, the initial stage, and short-term or working memory, the second stage, which persists for about 18 to 30 seconds. LTM is grouped into two categories known as explicit memory (declarative memory) and implicit memory (non-declarative memory). Explicit memory is broken down into episodic and semantic memory, while implicit memory includes procedural memory and emotional conditioning.

Stores

The idea of separate memories for short- and long-term storage originated in the 19th century. One model of memory developed in the 1960s assumed that all memories are formed in one store and transfer to another store after a small period of time. This model is referred to as the "modal model", most famously detailed by Shiffrin. The model states that memory is first stored in sensory memory, which has a large capacity but can only maintain information for milliseconds. A representation of that rapidly decaying memory is moved to short-term memory. Short-term memory does not have a large capacity like sensory memory but holds information for seconds or minutes. The final storage is long-term memory, which has a very large capacity and is capable of holding information possibly for a lifetime.

The exact mechanisms by which this transfer takes place, whether all or only some memories are retained permanently, and even to have the existence of a genuine distinction between stores, remain controversial.

Evidence

Anterograde amnesia

One form of evidence cited in favor of the existence of a short-term store comes from anterograde amnesia, the inability to learn new facts and episodes. Patients with this form of amnesia have an intact ability to retain small amounts of information over short time scales (up to 30 seconds) but have little ability to form longer-term memories (illustrated by patient HM). This is interpreted as showing that the short-term store is protected from damage and diseases.

Distraction tasks

Other evidence comes from experimental studies showing that some manipulations impair memory for the 3 to 5 most recently learned words of a list (it is presumed that they are held in short-term memory). Recall for words from earlier in the list (it is presumed, stored in long-term memory) are unaffected. Other manipulations (e.g., semantic similarity of the words) affect only memory for earlier list words, but do not affect memory for the most recent few words. These results show that different factors affect short-term recall (disruption of rehearsal) and long-term recall (semantic similarity). Together, these findings show that long-term memory and short-term memory can vary independently of each other.

Models

Unitary model

Not all researchers agree that short- and long-term memory are separate systems. The alternative Unitary Model proposes that short-term memory consists of temporary activations of long-term representations (that there is one memory that behaves variously over all time scales, from milliseconds to years). It has been difficult to identify a sharp boundary between short- and long-term memory. Eugen Tarnow, a physics researcher, reported that the recall probability versus latency curve is a straight line from 6 to 600 seconds, with the probability of failure to recall only saturating after 600 seconds. If two different stores were operating in this time domain, it is reasonable to expect a discontinuity in this curve. Other research has shown that the detailed pattern of recall errors looks remarkably similar to recall of a list immediately after learning (it is presumed, from short-term memory) and recall after 24 hours (necessarily from long-term memory).

Further evidence for a unified store comes from experiments involving continual distractor tasks. In 1974, Bjork and Whitten, psychology researchers, presented subjects with word pairs to remember; before and after each word pair, subjects performed a simple multiplication task for 12 seconds. After the final word-pair, subjects performed the multiplication distractor task for 20 seconds. They reported that the recency effect (the increased probability of recall of the last items studied) and the primacy effect (the increased probability of recall of the first few items) was sustained. These results are incompatible with a separate short-term memory as the distractor items should have displaced some of the word-pairs in the buffer, thereby weakening the associated strength of the items in long-term memory.

Ovid Tzeng (1973) reported an instance where the recency effect in free recall did not seem to result from a short-term memory store. Subjects were presented with four study-test periods of 10-word lists, with a continual distractor task (20-second period of counting-backward). At the end of each list, participants had to free recall as many words as possible. After recall of the fourth list, participants were asked to recall items from all four lists. Both the initial and final recall showed a recency effect. These results violated the predictions of a short-term memory model, where no recency effect would be expected.

Koppenaal and Glanzer (1990) attempted to explain these phenomena as a result of the subjects' adaptation to the distractor task, which allowed them to preserve at least some short-term memory capabilities. In their experiment, the long-term recency effect disappeared when the distractor after the last item differed from the distractors that preceded and followed the other items (e.g., arithmetic distractor task and word reading distractor task). Thapar and Greene challenged this theory. In one of their experiments, participants were given a different distractor task after every study item. According to Koppenaal and Glanzer's theory, no recency effect would be expected as subjects would not have had time to adapt to the distractor; yet such a recency effect remained in place in the experiment.

Another explanation

One proposed explanation for recency in a continual distractor condition, and its disappearance in an end-only distractor task is the influence of contextual and distinctive processes. According to this model, recency is a result of the similarity of the final items' processing context to the processing context of the other items and the distinctive position of the final items versus intermediate items. In the end distractor task, the processing context of the final items is no longer similar to that of the other list items. At the same time, retrieval cues for these items are no longer as effective as without the distractor. Therefore, recency recedes or vanishes. However, when distractor tasks are placed before and after each item, recency returns, because all the list items have similar processing context.

Dual-store memory model

According to George Miller, whose paper in 1956 popularized the theory of the "magic number seven", short-term memory is limited to a certain number of chunks of information, while long-term memory has a limitless store.

Atkinson–Shiffrin memory model

According to the dual store memory model proposed in 1968 by Richard C. Atkinson and Richard Shiffrin, memories can reside in the short-term "buffer" for a limited time while they are simultaneously strengthening their associations in LTM. When items are first presented, they enter short-term memory for approximately twenty to thirty seconds, but due to its limited space, as new items enter, older ones are pushed out. The limit of items that can be held in the short-term memory is an average between four and seven, yet, with practice and new skills that number can be increased. However, each time an item in short-term memory is rehearsed, it is strengthened in long-term memory. Similarly, the longer an item stays in short-term memory, the stronger its association becomes in long-term memory.

Baddeley's model of working memory

Main article: Baddeley's model of working memory

In 1974, Baddeley and Hitch proposed an alternative theory of short-term memory, Baddeley's model of working memory. According to this theory, short-term memory is divided into different slave systems for different types of input items, and there is an executive control supervising what items enter and exit those systems. The slave systems include the phonological loop, the visuo-spatial sketchpad, and the episodic buffer (later added by Baddeley).

Encoding of information

LTM encodes information semantically for storage, as researched by Baddeley. In vision, the information needs to enter working memory before it can be stored into LTM. This is evidenced by the fact that the speed with which information is stored into LTM is determined by the amount of information that can be fit, at each step, into visual working memory. In other words, the larger the capacity of working memory for certain stimuli, the faster will these materials be learned.

Synaptic consolidation is the process by which items are transferred from short- to long-term memory. Within the first minutes or hours after acquisition, the engram (memory trace) is encoded within synapses, becoming resistant (though not immune) to interference from outside sources.

As LTM is subject to fading in the natural forgetting process, maintenance rehearsal (several recalls/retrievals of memory) may be needed to preserve long-term memories. Individual retrievals can take place in increasing intervals in accordance with the principle of spaced repetition. This can happen quite naturally through reflection or deliberate recall (also known as recapitulation), often dependent on the perceived importance of the material. Using testing methods as a form of recall can lead to the testing effect, which aids long-term memory through information retrieval and feedback.

In LTM, brain cells fire in specific patterns. When someone experiences something in the world, the brain responds by creating a pattern of specific nerves firing in a specific way to represent the experience. This is called distributed representation. Distributed representation can be explained through a scientific calculator. At the top of the calculator is an opening in which the numbers typed in show up. This small slot is compiled by many blocks that light up to show a specific number. In that sense, certain blocks light up when prompted to show the number 4, but other blocks light up to show the number 5. There may be overlap in the blocks used, but ultimately, these blocks are able to generate different patterns for each specific situation. The encoding of specific episodic memories can be explained through distributed representation. When you try to remember an experience, perhaps your friend's birthday party a year ago, your brain is activating a certain pattern of neurons. If you try to remember your mother's birthday party, another pattern of neurons is fired but there may be overlap because they are both birthday parties. This kind of remembering is the idea of retrieval because it involves recalling the specific distributed representation created during the encoding of the experience.

Sleep

Some theories consider sleep to be an important factor in establishing well-organized long-term memories. (See also sleep and learning.) Sleep plays a key function in the consolidation of new memories.

According to Tarnow's theory, long-term memories are stored in dream format (reminiscent of Penfield & Rasmussen's findings that electrical excitations of the cortex give rise to experiences similar to dreams). During waking life an executive function interprets LTM consistent with reality checking (Tarnow 2003). It is further proposed in the theory that the information stored in memory, no matter how it was learned, can affect performance on a particular task without the subject being aware that this memory is being used. Newly acquired declarative memory traces are believed to be reactivated during NonREM sleep to promote their hippocampo-neocortical transfer for long-term storage. Specifically, new declarative memories are better remembered if recall follows Stage II non-rapid eye movement sleep. The reactivation of memories during sleep can lead to lasting synaptic changes within certain neural networks. It is the high spindle activity, low oscillation activity, and delta wave activity during NREM sleep that helps to contribute to declarative memory consolidation. In learning before sleep, spindles are redistributed to neuronally active up-states within slow oscillations during NREM sleep. Sleep spindles are thought to induce synaptic changes and thereby contribute to memory consolidation during sleep. Here, we examined the role of sleep in the object-place recognition task, a task closely comparable to tasks typically applied for testing human declarative memory: It is a one-trial task, hippocampus-dependent, not stressful and can be repeated within the same animal. Sleep deprivation reduces vigilance or arousal levels, affecting the efficiency of certain cognitive functions such as learning and memory.

The theory that sleep benefits memory retention is not a new idea. It has been around since Ebbinghaus's experiment on forgetting in 1885. More recently studies have been done by Payne and colleagues and Holtz and colleagues. In Payne and colleague's experiment participants were randomly selected and split into two groups. Both groups were given semantically related or unrelated word pairs, but one group was given the information at 9 A.M. and the other group received theirs at 9 P.M. Participants were then tested on the word pairs at one of three intervals 30 minutes, 12 hours, or 24 hours later. It was found that participants who had a period of sleep between the learning and testing sessions did better on the memory tests. This information is similar to other results found by previous experiments by Jenkins and Dallenbach (1924). It has also been found that many domains of declarative memory are affected by sleep such as emotional memory, semantic memory, and direct encoding.

Holtz found that not only does sleep affect consolidation of declarative memories, but also procedural memories. In this experiment, fifty adolescent participants were taught either word pairs (which represents declarative memory) and a finger tapping task (procedural memory) at one of two different times of day. What they found was that the procedural finger tapping task was best encoded and remembered directly before sleep, but the declarative word pairs task was better remembered and encoded if learned at 3 in the afternoon.

Divisions

The brain does not store memories in one unified structure. Instead, different types of memory are stored in different regions of the brain. LTM is typically divided up into two major headings: explicit memory and implicit memory.

Explicit memory

Explicit memory (or declarative memory) refers to all memories that are consciously available. These are encoded by the hippocampus, entorhinal cortex, and perirhinal cortex, but consolidated and stored elsewhere. The precise location of storage is unknown, but the temporal cortex has been proposed as a likely candidate. Research by Meulemans and Van der Linden (2003) found that amnesiac patients with damage to the medial temporal lobe performed more poorly on explicit learning tests than did healthy controls. However, these same amnesiac patients performed at the same rate as healthy controls on implicit learning tests. This implies that the medial temporal lobe is heavily involved in explicit learning, but not in implicit learning.

Declarative memory has three major subdivisions:

Episodic memory

Episodic memory refers to memory for specific events in time, as well as supporting their formation and retrieval. Some examples of episodic memory would be remembering someone's name and what happened at your last interaction with each other. Experiments conducted by Spaniol and colleagues indicated that older adults have worse episodic memories than younger adults because episodic memory requires context dependent memory. It is said that episodic memories are not as detailed or accurate as people grow older in age. Some people may begin to have issues with identification or presentation related things as they age. They may not be able to recall things from their memory or have as good of a storage for details as they may have been able to do in the past. The Hippocampus is responsible for the functions of episodic memory and research suggests that the use of exercise can be effective in improving brain functions such as the episodic memory. According to Damien Moore and Paul D. Loprinzi, episodic memory can be improved using long-term potentiation, which is when synapses are made to be more durable with exercise. The durability and healthiness of the synapses will in time be able to pick up more connections with neurons and eventually help with episodic memory. Mnemonic training has also been proven to be effective with the sharpening of episodic memory. These trainings include things like the alphabet, music, numerical systems, and other learning systems. Studies by Shuyuan Chen and Zhihui Cai have shown that mnemonic training has shown to be able to improve episodic memory long term.

Semantic memory

Semantic memory refers to knowledge about factual information, such as the meaning of words. Semantic memory is independent information such as information remembered for a test. In contrast with episodic memory, older adults and younger adults do not show much of a difference in semantic memory, presumably because semantic memory does not depend on context memory.

Autobiographical memory

Autobiographical memory refers to knowledge about events and personal experiences from an individual's own life. Autographical memories are facilitated by aids including verbal, face-evoked, picture-evoked, odour-evoked, and music-evoked autobiographical memory cues. Though similar to episodic memory, it differs in that it contains only those experiences which directly pertain to the individual, from across their lifespan. Conway and Pleydell-Pearce (2000) argue that this is one component of the self-memory system.

Implicit memory

Implicit memory (procedural memory) refers to the use of objects or movements of the body, such as how exactly to use a pencil, drive a car, or ride a bicycle. This type of memory is encoded, and it is presumed stored by the striatum and other parts of the basal ganglia. The basal ganglia is believed to mediate procedural memory and other brain structures and is largely independent of the hippocampus. Research by Manelis, Hanson, and Hanson (2011) found that the reactivation of the parietal and occipital regions was associated with implicit memory. Procedural memory is considered non-declarative memory or unconscious memory which includes priming and non-associative learning. The first part of nondeclarative memory (implicit memory) involves priming. Priming occurs when you do something faster after you have already done that activity, such as writing or using a fork. Other categories of memory may also be relevant to the discussion of LTM. For example:

Emotional memory, the memory for events that evoke a particularly strong emotion, is a domain that can involve both declarative and procedural memory processes. Emotional memories are consciously available, but elicit a powerful, unconscious physiological reaction. Research indicates that the amygdala is extremely active during emotional situations and acts with the hippocampus and prefrontal cortex in the encoding and consolidation of emotional events.

Working memory is not part of LTM but is important for it to function. Working memory holds and manipulates information for a short period of time, before it is either forgotten or encoded into LTM. Then, in order to remember something from LTM, it must be brought back into working memory. If working memory is overloaded, it can affect the encoding of LTM. If one has a good working memory, they may have a better LTM encoding.

Disorders of memory

Main article: Memory disorder

Minor slips and lapses of memory are fairly commonplace and may increase naturally with age, when ill, or under stress. Some women may experience more memory lapses following the onset of the menopause. In general, more serious problems with memory occur due to traumatic brain injury or neurodegenerative disease.

Traumatic brain injury

The majority of findings on memory have been the result of studies that lesioned specific brain regions in rats or primates, but some of the most important work has been the result of accidental or inadvertent brain trauma. The most famous case in recent memory studies is the case study of HM, who had parts of his hippocampus, parahippocampal cortices, and surrounding tissue removed in an attempt to cure his epilepsy. His subsequent total anterograde amnesia and partial retrograde amnesia provided the first evidence for the localization of memory function, and further clarified the differences between declarative and procedural memory.

Neurodegenerative diseases

Many neurodegenerative diseases can cause memory loss. Some of the most prevalent (and, as a consequence, most intensely researched) include Alzheimer's disease, dementia, Huntington's disease, multiple sclerosis, and Parkinson's disease. None act specifically on memory; instead, memory loss is often a casualty of generalized neuronal deterioration. Currently, these illnesses are irreversible, but research into stem cells, psychopharmacology, and genetic engineering holds much promise.

Those with Alzheimer's disease generally display symptoms such as getting momentarily lost on familiar routes, placing possessions in inappropriate locations, and distortions of existing memories or completely forgetting memories. Researchers have often used the Deese–Roediger–McDermott paradigm (DRM) to study the effects of Alzheimer's disease on memory. The DRM paradigm presents a list of words such as doze, pillow, bed, dream, nap, etc., but no theme word is presented. In this case, the theme word would have been "sleep." Alzheimer's disease patients are more likely to recall the theme word as being part of the original list than healthy adults. There is a possible link between longer encoding times and increased false memory in LTM. The patients end up relying on the gist of the information instead of the specific words themselves. Alzheimer's disease leads to an uncontrolled inflammatory response brought on by extensive amyloid deposition in the brain, which leads to cell death in the brain. This gets worse over time and eventually leads to cognitive decline after the loss of memory. Pioglitazone may improve cognitive impairments, including memory loss, and may help protect long-term and visuospatial memory from neurodegenerative diseases.

Parkinson's disease patients have problems with cognitive performance; these issues resemble those seen in frontal lobe patients and can often lead to dementia. It is thought that Parkinson's disease is caused by degradation of the dopaminergic mesocorticolimbic projection originating from the ventral tegmental area. It has also been indicated that the hippocampus plays an important role in episodic and spatial (parts of LTM) memory, and Parkinson's disease patients have abnormal hippocampuses resulting in abnormal LTM functioning. L-dopa injections are often used to try to relieve Parkinson's disease symptoms, as well as behavioral therapy.

Schizophrenia patients have trouble with attention and executive functions, which in turn affects LTM consolidation and retrieval. They cannot encode or retrieve temporal information properly, which causes them to select inappropriate social behaviors. They cannot effectively use the information they possess. The prefrontal cortex, where schizophrenia patients have structural abnormalities, is involved with the temporal lobe and also affects the hippocampus, which causes their difficulty in encoding and retrieving temporal information (including LTM).

Biological underpinnings at the cellular level

Long-term memory, unlike short-term memory, is dependent upon the synthesis of new proteins. This occurs within the cellular body, and concerns the particular transmitters, receptors, and new synapse pathways that reinforce the communicative strength between neurons. The production of new proteins devoted to synapse reinforcement is triggered after the release of certain signaling substances (such as calcium within hippocampal neurons) in the cell. In the case of hippocampal cells, this release is dependent upon the expulsion of magnesium (a binding molecule) that is expelled after significant and repetitive synaptic signaling. The temporary expulsion of magnesium frees NMDA receptors to release calcium in the cell, a signal that leads to gene transcription and the construction of reinforcing proteins. For more information, see long-term potentiation (LTP).

One of the newly synthesized proteins in LTP is also critical for maintaining LTM. This protein is an autonomously active form of the enzyme protein kinase C (PKC), known as PKMζ. PKMζ maintains the activity-dependent enhancement of synaptic strength and inhibiting PKMζ erases established long-term memories, without affecting short-term memory or, once the inhibitor is eliminated, the ability to encode and store new long-term memories is restored.

Also, BDNF is important for the persistence of long-term memories.

The long-term stabilization of synaptic changes is also determined by a parallel increase of pre- and postsynaptic structures such as synaptic boutons, dendritic spines, and postsynaptic density. On the molecular level, an increase of the postsynaptic scaffolding proteins PSD-95 and HOMER1c has been shown to correlate with the stabilization of synaptic enlargement.

The cAMP response element-binding protein (CREB) is a transcription factor which is believed to be important in consolidating short- to long-term memories, and which is believed to be downregulated in Alzheimer's disease.

DNA methylation and demethylation

Rats exposed to an intense learning event may retain a life-long memory of the event, even after a single training session. The LTM of such an event appears to be initially stored in the hippocampus, but this storage is transient. Much of the long-term storage of the memory seems to take place in the anterior cingulate cortex. When such an exposure was experimentally applied, more than 5,000 differently methylated DNA regions appeared in the hippocampus neuronal genome of the rats at one and at 24 hours after training. These alterations in methylation pattern occurred at many genes that were down-regulated, often due to the formation of new 5-methylcytosine sites in CpG rich regions of the genome. Furthermore, many other genes were upregulated, likely often due to hypomethylation. Hypomethylation often results from the removal of methyl groups from previously existing 5-methylcytosines in DNA. Demethylation is carried out by several proteins acting in concert, including TET enzymes as well as enzymes of the DNA base excision repair pathway (see Epigenetics in learning and memory). The pattern of induced and repressed genes in brain neurons subsequent to an intense learning event likely provides the molecular basis for a LTM of the event.

Contradictory evidence

A couple of studies have had results that contradict the dual-store memory model. Studies showed that in spite of using distractors, there was still both a recency effect for a list of items and a contiguity effect.

Another study revealed that how long an item spends in short-term memory is not the key determinant in its strength in long-term memory. Instead, whether the participant actively tries to remember the item while elaborating on its meaning determines the strength of its store in LTM.

Single-store memory model

An alternative theory is that there is only one memory store with associations among items and their contexts. In this model, the context serves as a cue for retrieval, and the recency effect is greatly caused by the factor of context. Immediate and delayed free recall will have the same recency effect because the relative similarity of the contexts still exists. Also, the contiguity effect still occurs because contiguity also exists between similar contexts.

Emotion and memory

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Emotion_and_memory

 

Emotion can have a powerful effect on humans and animals. Numerous studies have shown that the most vivid autobiographical memories tend to be of emotional events, which are likely to be recalled more often and with more clarity and detail than neutral events.

The activity of emotionally enhanced memory retention can be linked to human evolution; during early development, responsive behavior to environmental events would have progressed as a process of trial and error. Survival depended on behavioral patterns that were repeated or reinforced through life and death situations. Through evolution, this process of learning became genetically embedded in humans and all animal species in what is known as flight or fight instinct.

Artificially inducing this instinct through traumatic physical or emotional stimuli essentially creates the same physiological condition that heightens memory retention by exciting neuro-chemical activity affecting areas of the brain responsible for encoding and recalling memory. This memory-enhancing effect of emotion has been demonstrated in many laboratory studies, using stimuli ranging from words to pictures to narrated slide shows, as well as autobiographical memory studies. However, as described below, emotion does not always enhance memory.

Arousal and valence in memory

One of the most common frameworks in the emotions field proposes that affective experiences are best characterized by two main dimensions: arousal and valence. The dimension of valence ranges from highly positive to highly negative, whereas the dimension of arousal ranges from calming or soothing to exciting or agitating.

The majority of studies to date have focused on the arousal dimension of emotion as the critical factor contributing to the emotional enhancement effect on memory. Different explanations have been offered for this effect, according to the different stages of memory formation and reconstruction. Memory has been shown to be better with arousal linked with emotion than without emotion. The use of a PET scan has allowed scientists to see that pictures with an "emotional-stimulus" have significantly larger amount of activity in the amygdala. In a study using fluoro-2-deoxyglucose (FDG-PET) to examine the brain during recall of films that were both neutral and aversive, there was a positive correlation between the brain glucose and metabolic rate in the amygdala. The activity in the amygalda is part of the episodic memory that was being created due to the adverse stimuli.

However, a growing body of research is dedicated to the emotional valence dimension and its effects on memory. It has been claimed that this is an essential step towards a more complete understanding of emotion effects on memory. The studies that did investigate this dimension have found that emotional valence alone can enhance memory; that is, nonarousing items with positive or negative valence can be better remembered than neutral items.

Emotion and encoding

From an information processing perspective, encoding refers to the process of interpreting incoming stimuli and combining the processed information. At the encoding level the following mechanisms have been suggested as mediators of emotion effects on memory:

Selectivity of attention

Easterbrook's (1959) cue utilization theory predicted that high levels of arousal will lead to attention narrowing, defined as a decrease in the range of cues from the stimulus and its environment to which the organism is sensitive. According to this hypothesis, attention will be focused primarily on the arousing details (cues) of the stimulus, so that information central to the source of the emotional arousal will be encoded while peripheral details will not.

Accordingly, several studies have demonstrated that the presentation of emotionally-arousing stimuli (compared to neutral stimuli) results in enhanced memory for central details (details central to the appearance or meaning of the emotional stimuli) and impaired memory for peripheral details. Also consistent with this hypothesis are findings of weapon focus effect, in which witnesses to a crime remember the gun or knife in great detail but not other details such as the perpetrator's clothing or vehicle. In laboratory replications it was found that participants spend a disproportionate amount of time looking at a weapon in a scene, and this looking time is inversely related to the likelihood that individuals will subsequently identify the perpetrator of the crime. Other researchers have suggested arousal may also increase the duration of attentional focusing on the arousing stimuli, thus delaying the disengagement of attention from it. Ochsner (2000) summarized the different findings and suggested that by influencing attention selectivity and dwell time, arousing stimuli are more distinctively encoded, resulting in more accurate memory of those stimuli.

While these previous studies focused on how emotion affects memory for emotionally arousing stimuli, in their arousal-biased competition theory, Mather and Sutherland (2011) argue that how arousal influences memory for non-emotional stimuli depends on the priority of those stimuli at the time of the arousal. Arousal enhances perception and memory of high priority stimuli but impairs perception and memory of low priority stimuli. Priority can be determined by bottom-up salience or by top-down goals.

Prioritized processing

Emotional items also appear more likely to be processed when attention is limited, suggesting a facilitated or prioritized processing of emotional information. This effect was demonstrated using the attentional blink paradigm in which 2 target items are presented in close temporal proximity within a stream of rapidly presented stimuli.

The typical finding is that participants often miss the second target item, as if there were a "blink" of attention following the first target's presentation, reducing the likelihood that the second target stimulus is attended. However, when the second target stimulus elicits emotional arousal (a "taboo" word), participants are less likely to miss the target's presentation, which suggests that under conditions of limited attention, arousing items are more likely to be processed than neutral items.

Additional support for the prioritized processing hypothesis was provided by studies investigating the visual extinction deficit. People suffering from this deficit can perceive a single stimulus in either side visual field if it is presented alone but are unaware of the same stimulus in the visual field opposed to the lesional side, if another stimulus is presented simultaneously on the lesional side.

Emotion has been found to modulate the magnitude of the visual extinction deficit, so that items that signal emotional relevance (e.g., spiders) are more likely to be processed in the presence of competing distractors than nonemotional items (e.g., flowers).

Emotion and storage

In addition to its effects during the encoding phase, emotional arousal appears to increase the likelihood of memory consolidation during the retention (storage) stage of memory (the process of creating a permanent record of the encoded information). A number of studies show that over time, memories for neutral stimuli decrease but memories for arousing stimuli remain the same or improve.

Others have discovered that memory enhancements for emotional information tend to be greater after longer delays than after relatively short ones. This delayed effect is consistent with the proposal that emotionally-arousing memories are more likely to be converted into a relatively permanent trace, whereas memories for nonarousing events are more vulnerable to disruption.

A few studies have even found that emotionally arousing stimuli enhance memory only after a delay. The most famous of these was a study by Kleinsmith and Kaplan (1963) that found an advantage for numbers paired with arousing words over those paired with neutral words only at delayed test, but not at immediate test. As outlined by Mather (2007), the Kleinsmith and Kaplan effects were most likely due to a methodological confound. However, Sharot and Phelps (2004) found better recognition of arousing words over neutral words at a delayed test but not at an immediate test, supporting the notion that there is enhanced memory consolidation for arousing stimuli. According to these theories, different physiological systems, including those involved in the discharge of hormones believed to affect memory consolidation, become active during, and closely following, the occurrence of arousing events.

Another possible explanation for the findings of the emotional arousal delayed effect is post-event processing regarding the cause of the arousal. According to the post stimulus elaboration (PSE) hypothesis, an arousing emotional experience may cause more effort to be invested in elaboration of the experience, which would subsequently be processed at a deeper level than a neutral experience. Elaboration refers to the process of establishing links between newly-encountered information and previously-stored information.

It has long been known that when individuals process items in an elaborative fashion, such that meaning is extracted from items and inter-item associations are formed, memory is enhanced. Thus, if a person gives more thought to central details in an arousing event, memory for such information is likely to be enhanced. However, these processes could also disrupt consolidation of memories for peripheral details. Christianson (1992) suggested that the combined action of perceptual, attentional, and elaborative processing, triggered by an emotionally arousing experience, produces memory enhancements of details related to the emotion laden stimulus, at the cost of less elaboration and consolidation of memory for the peripheral details.

Emotion and elaboration

The processes involved in this enhancement may be distinct from those mediating the enhanced memory for arousing items. It has been suggested that in contrast to the relatively automatic attentional modulation of memory for arousing information, memory for non-arousing positive or negative stimuli may benefit instead from conscious encoding strategies, such as elaboration. This elaborative processing can be autobiographical or semantic.

Autobiographical elaboration is known to benefit memory by creating links between the processed stimuli, and the self, for example, deciding whether a word would describe the personal self. Memory formed through autobiographical elaboration is enhanced as compared to items processed for meaning, but not in relation to the self.

Since words such as "sorrow" or "comfort" may be more likely to be associated with autobiographical experiences or self-introspection than neutral words such as "shadow", autobiographical elaboration may explain the memory enhancement of non-arousing positive or negative items. Studies have shown that dividing attention at encoding decreases an individual's ability to utilize controlled encoding processes, such as autobiographical or semantic elaboration.

Thus, findings that participants' memory for negative non-arousing words suffers with divided attention, and that the memory advantage for negative, non-arousing words can be eliminated when participants encode items while simultaneously performing a secondary task, has supported the elaborative processing hypothesis as the mechanism responsible for memory enhancement for negative non-arousing words.

Emotion and retrieval

Retrieval is a process of reconstructing past experiences; this phenomenon of reconstruction is influenced by a number of different variables described below.

Trade-off between details

Kensinger argues there are two trade-offs: central/peripheral trade-off of details and a specific/general trade-off. Emotional memories may include increased emotional details often with the trade-off of excluding background information. Research has shown that this trade-off effect cannot be explained exclusively by overt attention (measured by eye-tracking directed to emotional items during encoding) (Steinmetz & Kensinger, 2013).

Contextual effects of emotion on memory

Contextual effects occur as a result of the degree of similarity between the encoding context and the retrieval context of an emotional dimension. The main findings are that the current mood we are in affects what is attended, encoded and ultimately retrieved, as reflected in two similar but subtly different effects: the mood congruence effect and mood-state dependent retrieval. Positive encoding contexts have been connected to activity in the right fusiform gyrus. Negative encoding contexts have been correlated to activity in the right amygdala (Lewis & Critchley, 2003). However, Lewis and Critchley (2003) claim that it is not clear whether involvement of the emotional system in encoding memory differs for positive or negative emotions, or whether moods at recall lead to activity in the corresponding positive or negative neural networks.

Mood congruence effect

The mood congruence effect refers to the tendency of individuals to retrieve information more easily when it has the same emotional content as their current emotional state. For instance, being in a depressed mood increases the tendency to remember negative events (Drace, 2013).

This effect has been demonstrated for explicit retrieval as well as implicit retrieval.

Mood-state dependent retrieval

Another documented phenomenon is the mood-state dependent retrieval, a type of context-dependent memory. The retrieval of information is more effective when the emotional state at the time of retrieval is similar to the emotional state at the time of encoding.

Thus, the probability of remembering an event can be enhanced by evoking the emotional state experienced during its initial processing. These two phenomena, the mood congruity effect, and mood-state dependent retrieval, are similar to the context effects which have been traditionally observed in memory research. It may also relate to the phenomena of state-dependent memory in neuropsychopharmacology.

When recalling a memory, if someone is recalling an event by themselves or within a group of people, the emotions that they remember may change as well recall of specific details. Individuals recall events with stronger negative emotions than when a group is recalling the same event. Collaborative recall, as it can be referred to, causes strong emotions to fade. Emotional tone changes as well, with a difference of individual or collaborative recall so much that an individual will keep the tone of what was previously felt, but the group will have a more neutral tone. For example, if someone is recalling the negative experience of taking a difficult exam, then they will talk in a negative tone. However, when the group is recalling taking the exam, they will most likely recount it in a positive tone as the negative emotions and tones fade. Detail recount is also something that changed based on the emotion state a person is in when they are remembering an event. If an event is being collaboratively recalled the specific detail count is higher than if an individual is doing it. Detail recall is also more accurate when someone is experiencing negative emotion; Xie and Zhang (2016) conducted a study in which participants saw a screen with five colors on it and when presented with the next screen were asked which color was missing. Those who were experiencing negative emotions were more precise than those in the positive and neutral conditions. Aside from emotional state, mental illness like depression relates to people's ability to recall specific details. Those who are depressed tend to overgeneralize their memories and are not able to remember as many specific details of any events as compared to those without depression.

Thematic vs. sudden appearance of emotional stimuli

A somewhat different contextual effect stemmed from the recently made distinction between thematical and sudden appearance of an emotionally arousing event, suggesting that the occurrence of memory impairments depends on the way the emotional stimuli are induced. Laney et al. (2003) argued that when arousal is induced thematically (i.e., not through the sudden appearance of a discrete shocking stimulus such as a weapon but rather through involvement in an unfolding event plot and empathy with the victim as his or her plight becomes increasingly apparent), memory enhancements of details central to the emotional stimulus need not come at the expense of memory impairment of peripheral details.

Laney et al. (2004) demonstrated this by using an audio narrative to give the presented slides either neutral or emotional meaning, instead of presenting shockingly salient visual stimuli. In one of the experiments, participants in both the neutral and emotional conditions viewed slides of a date scenario of a woman and man at a dinner date. The couple engaged in conversation, then, at the end of the evening, embraced. The event concluded with the man leaving and the woman phoning a friend.

The accompanying audio recording informed participants in the neutral condition that the date went reasonably well, while participants in the emotional condition heard that, as the evening wore on, the man displayed some increasingly unpleasant traits of a type that was derogatory to women, and the embrace at the end of the evening was described as an attempt to sexually assault the woman.

As expected, the results revealed that details central to the event were remembered more accurately when that event was emotional than when neutral, However, this was not at the expense of memory for peripheral (in this case, spatially peripheral or plot-irrelevant) details, which were also remembered more accurately when the event was emotional. Based on these findings it has been suggested that the dual enhancing and impairing effects on memory are not an inevitable consequence of emotional arousal.

Memory of felt emotion

Many researchers use self-report measures of felt emotion as a manipulation check. This raises an interesting question and a possible methodological weakness: are people always accurate when they recall how they felt in the past? Several findings suggest this is not the case. For instance, in a study of memory for emotions in supporters of former U.S. presidential candidate Ross Perot, supporters were asked to describe their initial emotional reactions after Perot's unexpected withdrawal in July 1992 and again after the presidential election that November.

Between the two assessment periods, the views of many supporters changed dramatically as Perot re-entered the race in October and received nearly a fifth of the popular vote. The results showed that supporters recalled their past emotions as having been more consistent with their current appraisals of Perot than they actually were.

Another study found that people's memories for how distressed they felt when they learned of the 9/11 terrorist attacks changed over time and moreover, were predicted by their current appraisals of the impact of the attacks (Levine et al., 2004). It appears that memories of past emotional responses are not always accurate, and can even be partially reconstructed based on their current appraisal of events.

Studies have shown that as episodic memory becomes less accessible over time, the reliance on semantic memory to remember past emotions increases. In one study Levine et al. (2009) primes of the cultural belief of women being more emotional than men had a greater effect on responses for older memories compared to new memories. The long-term recall of emotions was more in line with the primed opinions, showing that long-term recall of emotions was heavily influenced by current opinions.

Emotion regulation effects on memory

An interesting issue in the study of the emotion-memory relationship is whether our emotions are influenced by our behavioral reaction to them, and whether this reaction—in the form of expression or suppression of the emotion—might affect what we remember about an event. Researchers have begun to examine whether concealing feelings influences our ability to perform common cognitive tasks, such as forming memories, and found that the emotion regulation efforts do have cognitive consequences. In the seminal work on negative affect arousal and white noise, Seidner found support for the existence of a negative affect arousal mechanism through observations regarding the devaluation of speakers from other ethnic origins."

In a study of Richards and Gross (1999) and Tiwari (2013), participants viewed slides of injured men that produced increases in negative emotions, while information concerning each man was presented orally with his slide. The participants were assigned to either an expressive suppression group (where they were asked to refrain from showing emotion while watching the slides) or to a control group (where they were not given regulatory instructions at all). As predicted by the researchers, suppressors showed significantly worse performance on a memory test for the orally presented information.

In another study, it was investigated whether expressive suppression (i.e., keeping one's emotions subdued) comes with a cognitive price. They measured expressive suppression when it spontaneously occurred while watching a movie of surgeries. After the movie, memory was tested and was found to be worse with a higher usage of suppression. In a second study, another movie was shown of people arguing. Memory of the conversation was then measured. When gauging the magnitude of cognitive cost, expressive suppression was compared with self-distraction, which was described as simply not trying to think about something. It was concluded that experimentally-induced suppression was associated with worse memory.

There is evidence that emotion enhances memory but is more specific towards arousal and valence factors. To test this theory, arousal and valence were assessed for over 2,820 words. Both negative and positive stimuli were remembered higher than neutral stimuli. Arousal also did not predict recognition memory. In this study, the importance of stimulus controls and experimental designs in research memory was highlighted. Arousal-related activities when affiliated with heightened heart rate (HR) stimulate prediction of memory enhancement. It was hypothesized that tonic elevations in HR (meaning revitalization in HR) and phasic HR (meaning quick reaction) declaration to help the memory. Fifty-three men's heart rates were measured while looking at unpleasant, neutral, and pleasant pictures and their memory tested two days later. It was concluded that tonic elevations created more accurate memory recall.

Several related studies have reached similar results. It was demonstrated that the effects of expressive suppression on memory generalize to emotionally positive experiences and to socially relevant contexts.

One possible answer to the question "why does emotion suppression impair memory?" might lay in the self monitoring efforts invested in order to suppress emotion (thinking about the behavior one is trying to control). A recent study found heightened self- monitoring efforts among suppressors relative to control participants.

That is, suppressors were more likely to report thinking about their behavior and the need to control it during a conversation. Increases in self-monitoring predicted decreases in memory for what was said, that is, people who reported thinking a lot about controlling their behavior had particularly impoverished memories. However, additional research is needed to confirm whether self-monitoring actually exerts a causal effect on memory

Emotion-induced forgetting

Further information: Motivated forgetting

Emotionally arousing stimuli can lead to retrograde amnesia for preceding events and anterograde amnesia for subsequent events. This has been demonstrated in lab studies with lists of words or pictures, in which people show impaired memory for stimuli appearing before or after arousing stimuli.

Depression and memory

Memory recall tends to be congruent with one's current mood, with depressed people more likely to recall negative events from the past. In addition, depression is often associated with poor memory in general, as outlined here.

Dementia and emotional memory

Several studies have demonstrated emotional memory enhancement in Alzheimer's patients suggesting that emotional memory enhancement might be used in the daily management of Alzheimer's patients. One study found that objects are recalled significantly better in Alzheimer's patients if they were presented as birthday presents to AD patients.

Aging and emotional memory

The enhancing effects of emotional arousal on later memory recall tend to be maintained among older adults and the amygdala shows relatively less decline than many other brain regions. However, older adults also show somewhat of a shift towards favoring positive over negative information in memory, leading to a positivity effect.

Emotional memory and sleep

Emotional memory and sleep has been a well-researched association. Emotional memories are consolidated greater during sleep, rather than neutral memories. Studies have investigated high valence and arousing words, in comparison to neutral words. Sleep enhances the consolidation of the high valence and arousing words and therefore these are remembered more post-sleep. This concept has been demonstrated in many studies using a variety of media such as pictures, film clips, and words.

Memories of 'future relevance' are also consolidated greater during sleep. In a study by Wilhelm et al., 2011, memories of items that participants knew were needed for the future (for the testing session) were remembered more after sleep. Sleep consolidated these memories of future relevance to a greater extent. Memories that are emotionally significant and relevant for the future are therefore preferentially consolidated during sleep. This can translate to mean that memories that are more meaningful or valuable to a person are consolidated more.

The concept of emotional memory and sleep can be applied to real-life situations e.g. by developing more effective learning strategies. One could integrate the memorization of information that possesses high emotional significance (highly salient) with information that holds little emotional significance (low salience), prior to a period of sleep.

Memory erasure

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Memory_erasure

Memory erasure is the selective artificial removal of memories or associations from the mind.

Overview

Memory erasure has been shown to be possible in some experimental conditions; some of the techniques currently being investigated are: drug-induced amnesia, selective memory suppression, destruction of neurons, interruption of memory, reconsolidation, and the disruption of specific molecular mechanisms.

There are many reasons that research is being done on the selective removal of memories. Potential patients for this research include patients with psychiatric disorders such as post traumatic stress disorder, or substance use disorder, among others.

Memory erasure is also featured in numerous works of fiction, with fictional methods and properties that do not necessarily correspond with scientific reality.

Recent history

Research focused on gaining a better understanding of what memories are has been going on for many years, in this way so has research in memory erasure. The basis for the recent history for memory erasure has been focused on determining how the brain actively keeps memories stored and retrieves them. There have been several instances where researchers found drugs that when applied to certain areas of the brain, usually the amygdala, have relative success in being able to erase some memories. As early as 2009 researchers were able to trace and destroy neurons involved in supporting the specific type of memory that they were trying to erase. These neurons were targeted by using replication-defective herpes simplex virus (HSV) to increase cyclic adenosine monophosphate response element-binding protein (CREB) in them. As a result, the neurons were activated in fear memory or testing far more often in both wild-type and CREB-deficient mice. For the study, transgenic mice were used that allowed use of diphtheria toxin to preferentially target cells that were overexpressing CREB, since these were the cells more likely involved with fear memories. This caused the erasure of the target memory but allowed the mice to still form new fear memories which confirmed the cells were involved only in storing fear memories and not forming them.

Aside from the biotechnology approach to studying memory, research in psychiatry on how memories work has also been going on for several years. There have been some studies that show that some behavioral therapy can erase bad memories. There has been some evidence that psychodynamic therapy and other energy techniques can help with forgetting memories among other psychiatric issues there is no proven therapeutic approach for trying to erase bad memories.

Potential patients

There are several different types of possible patients that have the potential to draw great benefit from the selective memory erasure; these include people with drug addiction, or posttraumatic stress disorder (PTSD). PTSD patients may include war veterans, people who witnessed horrific events, victims of violent crimes and many other possibly traumatic events. These potential patients have unwanted memories that can be absolutely devastating to their daily lives and cause them to not be able to function properly.

Research continues, and in 2020, researchers were looking at potential new approaches to PTSD treatment.

Different types of memories

There are three main types of memories: sensory memory, short-term memory, and long-term memory. Sensory memory, in short, is the ability to hold sensory information for a short period of time, for example, looking at an object and being able to remember what it looked like moments after. Short-term memory is memory that allows a person to recall a short period of time; this can be a few seconds to a minute. Short-term memory allows people to remember what happened during that short time span without actually practicing the memory. Long-term memory has a much larger capacity than the prior two and actually stores information from both these types of memories to create a long lasting and large memory. Long-term memory is the largest target for research involving selective memory erasure.

Within long-term memory there are several types of retention. Implicit memory (or 'muscle memory') is generally described as the ability to remember how to use objects or specific movements of the body (e.g. using a hammer). Explicit memory, (or 'declarative memory') is that which can be consciously drawn upon by a person to remember.

Explicit memory can be split into further subcategories; episodic memory, which is the memory of specific events and the information surrounding it, and semantic memory, which is the ability to remember factual information (e.g. what numbers mean).

A type of memory of main concern for memory erasure are emotional memories. These memories often involve several different aspects of information in them that can come from a variety of the different categories of memories mentioned above. These emotional memories are powerful memories that can illicit strong physiological effects on a person. An example of an emotional memory can be found in patients with PTSD, for these patients a traumatic event has left a lasting emotional memory that can have powerful effects on a person even without them consciously retrieving the memory.

Current research

Drug-induced amnesia

Drug-induced amnesia is the idea of selectively losing or inhibiting the creation of memories using drugs. Amnesia can be used as a treatment for patients who have experienced psychological trauma or for medical procedures where full anesthesia is not an option. Drug-induced amnesia is also a side-effect of other drugs like alcohol and rohypnol.

There are other drugs that also can cause their users to be put in an amnesic state, where they experience some type of amnesia because of their use. Examples of these drugs include Triazolam, Midazolam and Diazepam.

Disruption of molecular mechanisms

There is a growing amount of information that has shown that memory depends largely on the brain's synaptic plasticity, with a large part of this being dependent on its ability to maintain long-term potentiation (LTP). Studies on LTP have also started to indicate that there are several molecular mechanisms that may be at the basis of memory storage. A more recent approach to erasing memories and the associations the brain makes with objects is disrupting specific molecular mechanisms in the brain that are actively keeping memories active.

Recovering methamphetamine (METH) addicts have reported that the sight of certain objects such as a lighter, gum or drug paraphernalia can cause massive cravings that can sometimes lead to a break in their mental strength and cause them to relapse. This indicates that long-term memories can be called upon by various different associations that were made with the memory without the conscious effort of the person. With an increasing belief that memories are largely supported by functional and structural plasticity deriving from F-actin polymerization in postsynaptic dendritic spines at excitatory synapses. Recent research has been done to target this F-actin polymerization by using direct actin depolymerization or a myosin II inhibitor to disrupt the polymerized F-actin associated with METH memory associations. The study indicated types of associations can be disrupted days to weeks after consolidation. Although the depolymerization techniques had no effect on food reward based associations or shock based associations the results demonstrate the idea that meth associated memories' actin cytoskeleton is constantly changing making it uniquely sensitive to depolymerization during the maintenance phase. This is some of the first evidence showing that memories made with different associations are actively maintained using different molecular substrates. These results also show that the actin cytoskeleton may be a promising target for selective disruption of unwanted long-term memories.

Selective memory suppression

Selective memory suppression is the idea that someone can consciously block an unwanted memory. Several different therapeutic techniques or training have been attempted to test this idea with varied success. Many of these techniques focus on blocking the retrieval of a memory using suppression techniques to slowly teach the brain to suppress the memory. Although some of these techniques have been useful for some people it has not been shown to be a clear cut solution to forgetting memories. Because these memories are not truly erased but merely suppressed the question of how permanent the solution is and what actually happens to the memories can be troubling for some.

Selective memory suppression is also something that can occur without a person being consciously aware of suppressing the creation and retrieval of unwanted memories. When this occurs without the person knowing it is usually referred to as memory inhibition; the memory itself is called a repressed memory.

Interruption of memory reconsolidation

One of the ways scientists have attempted to erase these memories through suppression is by interrupting the reconsolidation of a memory. Memory consolidation of a memory is when a person recalls a memory, usually a fearful one, it becomes susceptible to alteration, and then gets stored again. This has led many researchers to believe that this time period is the best time for memories to be altered or erased. Studies have shown that through behavioral training results showed that they were able to erase memories by tampering with memories during the reconsolidation phase.

Destruction of neurons

With evidence showing that different memories excite different neurons or system of neurons in the brain^[23] the technique of destroying select neurons in the brain to erase specific memories is also being researched. Studies have started to investigate the possibility of using distinct toxins along with biotechnology that allows the researchers to see which areas of the brain are being used during the reward learning process of making a memory to destroy target neurons. In a paper published in 2009, authors showed that neurons in the lateral amygdala that had a higher level of cyclic adenosine monophosphate response element-binding protein (CREB) were activated primarily over other neurons by fear memory expression. This indicated to them that these neurons were directly involved in the making of the memory trace for that fear memory. They then proceeded to train mice using auditory fear training to produce a fear memory. They proceeded to check which of the neurons were overexpressing CREB and then, using an inducible diphtheria-toxin strategy, they destroyed those neurons, resulting in persistent and strong memory erasure of the fear memory.

Researchers have also found that the levels of the neurotransmitter, acetylcholine, can also effect which memories are most prominent in our minds.

Due to the lack of understanding of the brain this technique of destroying neurons may have a much larger effect on the patient than just the removal of the intended memories. Due to this complex nature of the brain treatment that would stun the neurons instead of destroying them could be another approach that could be taken.

Optogenetics

A way of selectively erasing memories may be possible through optogenetics, a type of gene therapy that targets specific neurons. In 2017, researchers at Stanford demonstrated a technique for observing hundreds of neurons firing in the brain of a live mouse, in real time, and have linked that activity to long-term information storage. By using a virus to trigger production of a light-sensitive protein in neurons linked to a fear, they could erase the memory by weakening the pathways using light.

Measurement issues

Further information: Mass action principle (neuroscience) and Memory consolidation § Multiple trace theory

There is an epistemological issue in determining whether the absence of evidence (i.e., memory trace) is evidence of absence. In experimental studies, the absence of behavior indicative of memory is sometimes interpreted as the absence of the memory trace; however, the memory impairment may be temporary due to deficits in recall. Alternatively, the memory trace be latent and demonstrable via its indirect effects on new learning^. The measurement issue is compounded by the fact that memory processes are dynamic and may not always manifest in single locations or in static and easily identifiable changes detectable by current technologies.

Michael Davis, researcher at Emory University, argues that complete erasure can only be confidently concluded if all of the biological events that occurred when the memory was formed revert to their original status. The current state of technology and methodology may not be sensitive enough to detect all types of memory traces. Davis contends that because making these measurements in a complex organism is implausible, the concept of complete memory erasure (what he deems "strong form of forgetting") is not useful scientifically.

Ethics

As with most new technologies the idea of being able to erase memories comes with many ethical questions. One ethical question that arises is the idea that although there are some extremely painful memories that some people (for example PTSD patients) would like to be rid of, not all unpleasant memories are bad. The ability to soften or erase memories could have drastic effects on how society functions. The ability to remember unpleasant effects from one's past has a huge impact on the future actions they may take. Remembering and learning from past mistakes is crucial in the emotional development of a person and helps to ensure they do not repeat previous errors. The ability to erase memory could also have a massive impact on the law. When it comes to determining the outcome of a trial, the ability to modify memory could have a massive impact on the judicial system. Another ethical question that arises is to how the government will use this technology and what restrictions would need to be put in place. Some worry that if soldiers can go into battle knowing that the memories created during that time period can simply be erased they may not uphold military morale and standards. Many are also skeptical with who should be able to have procedures done on them, so they are urging for a set of laws to determine this.

In fiction

Memory erasure has also been a common topic of interest in science fiction and other fiction. Several notable comics, TV shows and movies feature mindwipes, including Telefon, Total Recall, Men in Black, Eternal Sunshine of the Spotless Mind, Black Mirror, The Bourne Identity, NBC's Heroes and Dollhouse. Novels that feature memory erasure include The Invincible by Stanisław Lem, some of the Harry Potter novels (including Harry Potter and the Chamber of Secrets) by J. K. Rowling, and The Giver by Lois Lowry. Several works by Philip K. Dick are about mindwipes, including "Paycheck", "We Can Remember It for You Wholesale" (which served as the inspiration for Total Recall).

Robotic pet

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Robotic_pet

Robotic pets are artificially intelligent machines that are made to resemble actual pets. While the first robotic pets produced in the late 1990s, were not too advanced, they have since grown technologically. Many now use machine learning (algorithms that allow machines to adapt to experiences independent of humans), making them much more realistic. Most consumers buy robotic pets with the aim of getting similar companionship that real pets offer, without some of the drawbacks that come with caring for live animals. The pets on the market currently have a wide price range, from the low hundreds into the several thousands of dollars. Multiple studies have been done to show that we treat robotic pets in a similar way as actual pets, despite their obvious differences. However, there is some controversy regarding how ethical using robotic pets is, and whether or not they should be widely adopted in elderly care.

History

The first known robotic pet was a robot dog called Sparko, built by the American company Westinghouse in 1940. It never got sold due to poor public interest.

The first robotic pets to be put on the market were Hasbro's Furby in 1998 and Sony's AIBO in 1999. Since then, robotic pets have grown increasingly advanced.

The shapes of the robotic pet includes:

• familiar animals
• nonfamiliar animals
• imaginary animals or characters

Some popular robotic pets today are:

• Joy for All (by Hasbro) Companion Pets
• Zoomer Interactive Animals (Usually Kittens and Puppies)
• PARO Robot Seals by Intelligent Systems Co.
• AIBO (upgraded) by Sony
• FurReal Friends by Hasbro
• Little Live Pets by Moose Toys
• EMO Pet by Living AI
• Hatchimals
• Pets Alive by the Hong Kong-based company ZURU
• Present Pets by Spin Master

Common Uses

The primary consumer group is elderly people that live alone or in nursing homes, who often suffer from loneliness and social isolation. For this group, robotic pets can be helpful because they often are unable to consistently walk, feed, or otherwise take care of an actual pet. Robotic pets are also marketed towards dementia patients, who are people that suffer from loss of memory and thinking skills. These people often suffer extreme loneliness due to not remembering their loved ones, but having physical contact and constant reminders of a robotic pet can lessen that feeling. For example, a study done in Texas and Kansas found that dementia residents who had group sessions with a PARO (brand of robotic pet) for three months showed decreased anxiety and less behavioral problems, when compared to a control group that experienced activities in a traditional nursing home, such as music and physical activity.

Robotic Pets can be helpful when it comes to patients unable to perform consistent physical action because AIBO performs slower than a live animal. In addition, patients unable to contact their loved ones due to infectious diseases can be eased the loneliness feeling when interacting with AIBO. The new AIBO ERS-1000 AIBO model can be used in household use or therapy. Furthermore, a Qualitative study associated with National Centre for Child Health and Development (NCCHD) has shown the bright future of robot-assisted therapy during special medical care. The experiment was conducted with children who were hospitalised in NCCHD; two physicians observed the participants throughout the experiment and rendered a qualitative analysis to evaluate the possibility of applying robotic Pet in medical. The result of the experiments in National Centre for Child Health and Development (NCCHD) was given out a dominant positive result when the children interact with AIBO (ERS-1000); the research has proved that robot-assisted therapy effectively in medical purposed, especially in this case is a paediatric ward.

Affordability

When robotic pets were first introduced into the market, they were not very financially feasible for most people. Even now, there remains a large price gap between different types of robotic pets. For example, PAROs robotic pet seals cost $6,120, making them unaffordable to most individual consumers. They are therefore bought more by nursing homes, hospitals, or other institutions. On the other end of the price spectrum are Joy For All's Companion Pets. These only cost about $120, which makes it more realistic for individual consumers, such as elderly adults who live alone.

Currently, there is very little insurance coverage available for robotic pet owners. Medicare only covers the costs of certain robotic pets (PARO) for use by therapists, not by any individuals. However, Medicaid and some private insurers are exploring the idea of including robotic pets in their healthcare. If this were to happen, it would significantly boost the sales of the pets.

In 2018, Sony relaunched their discontinued AIBO with a friendly puppy appearance; the new model was released with various significant upgrades compared to the ERS-7 model. The price for a 2018 AIBO (ERS-1000) falls around US$3.000; the price has gone up due to a new design with state of the art sensors integrated into the ERS-1000 model.

Effectiveness

Since the effectiveness of a robotic pet depends heavily on how much consumers see it as a real animal, multiple studies have been done comparing robotic pets to other things, such as live animals and inanimate objects (toys). The studies often focus on whether the robot / animal / toy is seen to have the following characteristics:

Characteristic	Definition	Example Question
Biological / Physical Essence	Whether or not something is alive	Can it eat?
Mental State	Whether or not something can have feelings	Can it be happy?
Sociability	Whether or not something is capable of being a companion	Can you be friends with it?
Moral Standing	Whether or not something is responsible for their actions	Can you justify physically punishing it if it does something wrong?

Robotic Pet vs Stuffed Animal

One study in 2004 compared how children interacted with Sony's AIBO versus with a stuffed dog. The researchers did this by letting the children play with either the stuffed toy or the AIBO for three minutes, and then asking the children a series of questions to determine how they viewed each one. The study found that, when the children were asked questions about the characteristics of either AIBO or the stuffed animal, they responded in similar ways. This held true when they were asked questions concerning biological essence, mental states, sociability, and moral standing. However, there were differences in how the children behaved with AIBO versus the stuffed animal. For example, in the questionnaire the children responded that both the AIBO and the stuffed dog could hear verbal commands. But when the researchers observed how the children interacted with the AIBO or stuffed dog, they found that more children gave verbal commands to the AIBO.

Robotic Pet vs Live Animal

Another study in 2005 compared children's interactions with the AIBO and with a live dog. The researchers did this by letting the children play freely with either the AIBO or the real dog for five minutes, and then asking the children a series of questions to determine how they viewed each one. The study found that more children preferred to play with the live dog over the AIBO, and more children affirmed that the live dog had a physical essence, a mental state, sociability, and moral standing. However, the researchers found that the AIBO was given some dog-like attributes, even if not treated entirely like the dog. For example, many of the children thought the AIBO could have feelings, such as happiness or sadness. Some also thought that the AIBO could be their friend, and that it wasn't okay to kick the AIBO if it did something bad.

Both these studies concluded that robotic pets such as AIBO often aren't categorized as either alive or inanimate, but rather in a new category in between the other two. For example, children in the first study treated the AIBO differently than they treated the stuffed toy, even though they stated that the two were very similar. In contrast, the children in the second study stated that the live dog was different from the AIBO, but ended up treating the two similarly. These findings show that we consciously identify robotic pets as inanimate objects, but we behave as if they are closer to real pets than they are to toys.

Animal Assisted Therapy vs Robot-Assisted Therapy

A study in the United States was conducted on animal-assisted therapy (AAT); the study was carried out to evaluate the effectiveness of the therapy pet method. Participants interact with animals as a pet owner plays with their Pet; the experiment's outcomes were reported with many physical and mental improvements for the participants. However, the concern of transmitted diseases from animals posed a reconsideration from institutions when they consider animal-assisted therapy. In addition, A qualified therapy animal requires a well-trained session and a licensed caregiver, which randomly escalate the operating fees to the service. Opposite to animal-assisted therapy, robot-assisted therapy overcomes the draws back of animal-assisted therapy, and there are studies conducted to justify the possibility of robotic Pet in the medical field. In the study, AIBO is the selected subject for the research. AIBO was used to companion Elderly and hospitalised children. The robot-assisted method has already been applied to many cases, namely aged care, workplace, vulnerable social groups. Robot-assisted therapy comes at a lower cost than animal-assisted therapy. The robot does not need to feed or a licensed professional trainer; ultimately, the robotic Pet hygienic standard is higher than live animals. AIBO-assisted therapy has given positive results, such as stimulating social-emotional function for vulnerable social groups and mental health well-being with elders in the aged-care facility.

The conclusion from the above studies, animal-assisted therapy (AAT) or robot-assisted therapy (RAT) has shown positive results from patients. Robot-assisted therapy can replace animal-assisted therapy in the particular unavoidable situation as social activity support for infectious illness patients, restricted movement patients, elderly whose vulnerable to animal transmitted diseases. In contrast, the animal-assisted therapy study's result shows the positive level of participants higher than robot-assisted therapy; this method was still limited by the cultural beliefs about the cleanliness of the animals; notably, the budget for this method is more pricey than the alternative therapy. Ultimately, with the advancement in robotic technology, robot-assisted therapy gradually can replace live animal therapy because of the safeness of the vulnerable target patient. also, the robot-assisted therapy had proved delightful positive results when it was conducted in a large scale study.

Controversy

While robotic pets have proven to be beneficial to many consumers, especially those who are elderly, there remains some controversy about certain ethical issues. One study from 2016 attempted to discuss two main ethical considerations: elderly consumers may not be able to recognize that the robots aren't actual pets, and that the robot pets will come to replace human interaction. Those who participated in the study came to the conclusion that for most consumers, neither issue is major concern. They found that most robotic pet owners understood that the robot pet was animated, even if they formed a pet-like relationship with it. Additionally, the study participants argued that the robotic pets would more likely be used in a way that facilitated more social interactions in a group setting, such as at a dog park. However, these issues continue to cause debate because there is a minority of consumers, including many dementia patients, who may fail to recognize that the robot is animated.

A robotic pet can mimic animal gestures, and the pet robot's design can look close to a natural pet. In this situation, AIBO ERS-1000 inherited an appearance close to a puppy, and the behaviour can be developed based on the owner interactions. The new AIBO was integrated with cloud memory. The data will be sent online to process and keep AIBO updated; with this function, AIBO behaviours can develop from a new puppy to a mature dog. A financial statistical about own a robot dog to compare with a domestic pet has visualised a financial picture that owns a robotic pet will save the owner from many unexpected issues as veterinary cost when a domestic pet need medical care, food and vaccination, adopt fee, training fee.