Caudate nucleus

From Wikipedia, the free encyclopedia

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

 

Caudate nucleus
Caudate nucleus (in red) shown within the brain
Transverse Cut of Brain (Horizontal Section), basal ganglia is blue
Details
Part of	dorsal striatum
Identifiers
Latin	nucleus caudatus
MeSH	D002421
NeuroNames	226
NeuroLex ID	birnlex_1373
TA98	A14.1.09.502
TA2	5561
FMA	61833
Anatomical terms of neuroanatomy

The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia. While the caudate nucleus has long been associated with motor processes due to its role in Parkinson's disease, it plays important roles in various other nonmotor functions as well, including procedural learning, associative learning and inhibitory control of action, among other functions. The caudate is also one of the brain structures which compose the reward system and functions as part of the cortico–basal ganglia–thalamic loop.

Structure

Caudate nucleus within the skull

Together with the putamen, the caudate forms the dorsal striatum, which is considered a single functional structure; anatomically, it is separated by a large white matter tract, the internal capsule, so it is sometimes also referred to as two structures: the medial dorsal striatum (the caudate) and the lateral dorsal striatum (the putamen). In this vein, the two are functionally distinct not as a result of structural differences, but merely due to the topographical distribution of function.

The caudate nuclei are located near the center of the brain, sitting astride the thalamus. There is a caudate nucleus within each hemisphere of the brain. Individually, they resemble a C-shape structure with a wider "head" (caput in Latin) at the front, tapering to a "body" (corpus) and a "tail" (cauda). Sometimes a part of the caudate nucleus is referred to as the "knee" (genu). The caudate head receives its blood supply from the lenticulostriate artery while the tail of the caudate receives its blood supply from the anterior choroidal artery.

Transverse view of the caudate nucleus from a structural MR image

The head and body of the caudate nucleus form part of the floor of the anterior horn of the lateral ventricle. After the body travels briefly towards the back of the head, the tail curves back toward the anterior, forming the roof of the inferior horn of the lateral ventricle. This means that a coronal (on a plane parallel to the face) section that cuts through the tail will also cross the body and head of the caudate nucleus.

Neurochemistry

The caudate is highly innervated by dopaminergic neurons that originate from the substantia nigra pars compacta (SNc). The SNc is located in the midbrain and contains cell projections to the caudate and putamen, utilizing the neurotransmitter dopamine. There are also additional inputs from various association cortices.

Motor functions

Spatial mnemonic processing

The caudate nucleus integrates spatial information with motor behavior formulation. Selective impairment of spatial working memory in subjects with Parkinson's disease and the knowledge of the disease's impact on the amount of dopamine supplied to the striatum have linked the caudate nucleus to spatial and nonspatial mnemonic processing. Spatially dependent motor preparation has been linked to the caudate nucleus through event-related fMRI analysis techniques. Activity in the caudate nucleus was demonstrated to be greater during tasks featuring spatial and motoric memory demands than those that involved nonspatial tasks. Specifically, spatial working memory activity has been observed, via fMRI studies of delayed recognition, to be greater in the caudate nucleus when the activity immediately preceded a motor response. These results indicate that the caudate nucleus could be involved in coding a motor response. With this in mind, the caudate nucleus could be involved in the recruitment of the motor system to support working memory performance by the mediation of sensory-motor transformations.

Directed movements

The caudate nucleus contributes importantly to body and limbs posture and the speed and accuracy of directed movements. Deficits in posture and accuracy during paw usage tasks were observed following the removal of caudate nuclei in felines. A delay in initiating performance and the need to constantly shift body position were both observed in cats following partial removal of the nuclei.

Following the application of cocaine to the caudate nucleus and the resulting lesions produced, a "leaping or forward movement" was observed in monkeys. Due to its association with damage to the caudate, this movement demonstrates the inhibitory nature of the caudate nucleus. The "motor release" observed as a result of this procedure indicates that the caudate nucleus inhibits the tendency for an animal to move forward without resistance.

Cognitive functions

Goal-directed action

A review of neuroimaging studies, anatomical studies of caudate connectivity, and behavioral studies reveals a role for the caudate in executive functioning. A study of Parkinson's patients (see below) may also contribute to a growing body of evidence.

A two-pronged approach of neuroimaging (including PET and fMRI) and anatomical studies expose a strong relationship between the caudate and cortical areas associated with executive functioning: "non-invasive measures of anatomical and functional connectivity in humans demonstrate a clear link between the caudate and executive frontal areas."

Meanwhile, behavioral studies provide another layer to the argument: recent studies suggest that the caudate is fundamental to goal-directed action, that is, "the selection of behavior based on the changing values of goals and a knowledge of which actions lead to what outcomes." One such study presented rats with levers that triggered the release of a cinnamon flavored solution. After the rats learned to press the lever, the researchers changed the value of the outcome (the rats were taught to dislike the flavor either by being given too much of the flavor, or by making the rats ill after drinking the solution) and the effects were observed. Normal rats pressed the lever less frequently, while rats with lesions in the caudate did not suppress the behavior as effectively. In this way, the study demonstrates the link between the caudate and goal-directed behavior; rats with damaged caudate nuclei had difficulty assessing the changing value of the outcome. In a 2003-human behavioral study, a similar process was repeated, but the decision this time was whether or not to trust another person when money was at stake. While here the choice was far more complex––the subjects were not simply asked to press a lever, but had to weigh a host of different factors––at the crux of the study was still behavioral selection based on changing values of outcomes.

In short, neuroimagery and anatomical studies support the assertion that the caudate plays a role in executive functioning, while behavioral studies deepen our understanding of the ways in which the caudate guides some of our decision-making processes.

Memory

The dorsal-prefrontal cortex subcortical loop involving the caudate nucleus has been linked to deficits in working memory, specifically in schizophrenic patients. Functional imaging has shown activation of this subcortical loop during working memory tasks in primates and healthy human subjects. The caudate may be affiliated with deficits involving working memory from before illness onset as well. Caudate nucleus volume has been found to be inversely associated with perseverative errors on spatial working memory tasks.

The amygdala sends direct projections to the caudate nucleus. Both the amygdala and the caudate nucleus have direct and indirect projections to the hippocampus. The influence of the amygdala on memory processing in the caudate nucleus has been demonstrated with the finding that lesions involving the connections between these two structures "block the memory-enhancing effects of oxotremorine infused into the caudate nucleus". In a study involving rats given water-maze training, the caudate nucleus was discovered to enhance memory of visually cued training after amphetamine was infused post-training into the caudate.

Learning

In a 2005 study, subjects were asked to learn to categorize visual stimuli by classifying images and receiving feedback on their responses. Activity associated with successful classification learning (correct categorization) was concentrated to the body and tail of the caudate, while activity associated with feedback processing (the result of incorrect categorization) was concentrated to the head of the caudate.

Sleep

Bilateral lesions in the head of the caudate nucleus in cats were correlated with a decrease in the duration of deep slow wave sleep during the sleep-wakefulness cycle. With a decrease in total volume of deep slow wave sleep, the transition of short-term memory to long-term memory may also be affected negatively. However, the effects of caudate nuclei removal on the sleep-wakefulness pattern of cats have not been permanent. Normalization has been discovered after a period of three months following caudate nuclei ablation. This discovery could be due to the inter-related nature of the roles of the caudate nucleus and the frontal cortex in controlling levels of central nervous system activation. The cats with caudate removal, although permanently hyperactive, had a significant decrease in rapid eye movement sleep (REMS) time that only lasted for about two months. However, afrontal cats had a permanent decrease in REMS time and only a temporary period of hyperactivity.

Contrasting with associations between "deep", REM sleep and the caudate nucleus, a study involving EEG and fMRI measures during human sleep cycles has indicated that the caudate nucleus demonstrates reduced activity during non-REM sleep across all sleep stages. Additionally, studies of human caudate nuclei volume in congenital central hypoventilation syndrome (CCHS) subjects established a correlation between CCHS and a significant reduction in left and right caudate volume. CCHS is a genetic disorder that affects the sleep cycle due to a reduced drive to breathe. Therefore, the caudate nucleus has been suggested to play a role in human sleep cycles.

Emotion

The caudate nucleus has been implicated in responses to visual beauty, and has been suggested as one of the "neural correlates of romantic love".

Approach-attachment behavior and affect are also controlled by the caudate nucleus. Cats with bilateral removal of the caudate nuclei persistently approached and followed objects, attempting to contact the target, while exhibiting a friendly disposition by the elicitation of treading of the forelimbs and purring. The magnitude of the behavioral responses was correlated to the extent of the removal of the nuclei. Reports of human patients with selective damage to the caudate nucleus show unilateral caudate damage resulting in loss of drive, obsessive-compulsive disorder, stimulus-bound perseverative behavior, and hyperactivity. Most of these deficits can be classified as relating to approach-attachment behaviors, from approaching a target to romantic love.

Language

Neuroimaging studies reveal that people who can communicate in multiple languages activate exactly the same brain regions regardless of the language. A 2006 publication studies this phenomenon and identifies the caudate as a center for language control. In perhaps the most illustrative case, a trilingual subject with a lesion to the caudate was observed. The patient maintained language comprehension in her three languages, but when asked to produce language, she involuntarily switched between the three languages. In short, "these and other findings with bilingual patients suggest that the left caudate is required to monitor and control lexical and language alternatives in production tasks."

Local shape deformations of the medial surface of the caudate have been correlated with verbal learning capacity for females and the number of perseverance errors on spatial and verbal fluency working memory tasks for males. Specifically, a larger caudate nucleus volume has been linked with better verbal fluency performance.

A neurological study of glossolalia showed a significant reduction in activity in the left caudate nucleus during glossolalia compared to singing in English.

Threshold control

The brain contains large collections of neurons reciprocally connected by excitatory synapses, thus forming large network of elements with positive feedback. It is difficult to see how such a system can operate without some mechanism to prevent explosive activation. There is some indirect evidence that the caudate may perform this regulatory role by measuring the general activity of cerebral cortex and controlling the threshold potential.

Clinical significance

Alzheimer's disease

A 2013 study has suggested a link between Alzheimer's patients and the caudate nucleus. MRI images were used to estimate the volume of caudate nuclei in patients with Alzheimer's and normal volunteers. The study found a "significant reduction in the caudate volume" in Alzheimer's patients when compared to the normal volunteers. While the correlation does not indicate causation, the finding may have implications for early diagnosis.

Parkinson's disease

Parkinson's disease is likely the most studied basal ganglia disorder. Patients with this progressive neurodegenerative disorder often first experience movement related symptoms (the three most common being tremors at rest, muscular rigidity, and akathisia) which are later combined with various cognitive deficiencies, including dementia. Parkinson's disease depletes dopaminergic neurons in the nigrostriatal tract, a dopamine pathway that is connected to the head of the caudate. As such, many studies have correlated the loss of dopaminergic neurons that send axons to the caudate nucleus and the degree of dementia in Parkinson's patients. And while a relationship has been drawn between the caudate and Parkinson's motor deficiencies, the caudate has also been associated with Parkinson's concomitant cognitive impairments. One review contrasts the performance of patients with Parkinson's and patients that strictly suffered from frontal-lobe damage in the Tower of London test. The differences in performance between the two types of patients (in a test that, in short, requires subjects to select appropriate intermediate goals with a larger goal in mind) draws a link between the caudate and goal-directed action. However, the studies are not conclusive. While the caudate has been associated with executive function (see "Goal-Directed Action"), it remains "entirely unclear whether executive deficits in [Parkinson's patients] reflect pre-dominantly their cortical or subcortical damage."

Huntington's disease

In Huntington's disease, a genetic mutation occurs in the HTT gene which encodes for Htt protein. The Htt protein interacts with over 100 other proteins, and appears to have multiple biological functions. The behavior of this mutated protein is not completely understood, but it is toxic to certain cell types, particularly in the brain. Early damage is most evident in the striatum, but as the disease progresses, other areas of the brain are also more conspicuously affected. Early symptoms are attributable to functions of the striatum and its cortical connections—namely control over movement, mood and higher cognitive function.

Attention-deficit hyperactivity disorder

A 2002 study draws a relationship between caudate asymmetry and symptoms related to ADHD. The authors used MR images to compare the relative volumes of the caudate nuclei (as the caudate is a bilateral structure), and drew a connection between any asymmetries and symptoms of ADHD: "The degree of caudate asymmetry significantly predicted cumulative severity ratings of inattentive behaviors." This correlation is congruent with previous associations of the caudate with attentional functioning. A more recent 2018 study replicated these findings, and demonstrated that the caudate asymmetries related to ADHD were more pronounced in the dorsal medial regions of the caudate.

Schizophrenia

The volume of white matter in the caudate nucleus has been linked with patients diagnosed with Schizophrenia. A 2004 study uses magnetic resonance imaging to compare the relative volume of white matter in the caudate among Schizophrenia patients. Those patients who suffer from the disorder have "smaller absolute and relative volumes of white matter in the caudate nucleus than healthy subjects."

Bipolar type I

A 2014 study found Type I Bipolar patients had relatively higher volume of gray and white matter in the caudate nucleus and other areas associated with reward processing and decision making, compared to controls and Bipolar II subjects. Overall the amount of gray and white matter in Bipolar patients was lower than controls.

Obsessive-compulsive disorder

It has been theorized that the caudate nucleus may be dysfunctional in persons with obsessive compulsive disorder (OCD), in that it may perhaps be unable to properly regulate the transmission of information regarding worrying events or ideas between the thalamus and the orbitofrontal cortex.

A neuroimaging study with positron emission tomography found that the right caudate nucleus had the largest change in glucose metabolism after patients had been treated with paroxetine. Recent SDM meta-analyses of voxel-based morphometry studies comparing people with OCD and healthy controls have found people with OCD to have increased grey matter volumes in bilateral lenticular nuclei, extending to the caudate nuclei, while decreased grey matter volumes in bilateral dorsal medial frontal/anterior cingulate gyri. These findings contrast with those in people with other anxiety disorders, who evince decreased (rather than increased) grey matter volumes in bilateral lenticular / caudate nuclei, while also decreased grey matter volumes in bilateral dorsal medial frontal/anterior cingulate gyri.

 

Curiosity

From Wikipedia, the free encyclopedia

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

Curious children gather around photographer Toni Frissell, looking at her camera (circa 1945)

Curiosity (from Latin cūriōsitās, from cūriōsus "careful, diligent, curious", akin to cura "care") is a quality related to inquisitive thinking such as exploration, investigation, and learning, evident by observation in humans and other animals. Curiosity is heavily associated with all aspects of human development, in which derives the process of learning and desire to acquire knowledge and skill.

The term curiosity can also be used to denote the behavior or emotion of being curious, in regard to the desire to gain knowledge or information. Curiosity as a behavior and emotion is attributed over millennia as the driving force behind not only human development, but developments in science, language, and industry.

Causes

Children peer over shoulders to see what their friends are reading.

Curiosity can be seen as an innate quality of many different species. It is common to human beings at all ages from infancy through adulthood, and is easy to observe in many other animal species; these include apes, cats, and rodents. Early definitions cite curiosity as a motivated desire for information. This motivational desire has been said to stem from a passion or an appetite for knowledge, information, and understanding.

These traditional ideas of curiosity have recently expanded to look at the difference between curiosity as the innate exploratory behavior that is present in all animals and curiosity as the desire for knowledge that is specifically attributed to humans.

Daniel Berlyne recognized three major variables playing a role in evoking curiosity; namely, psychophysical variables, ecological variables, and collative variables. Psychophysical variables correspond to physical intensity, while ecological variables to motivational significance and task relevance. Collative variables are called “collative” because they involve a comparison between different stimuli or features, which may be actually perceived or which may be recalled from memory. Berlyne mentioned four collative variables; namely, novelty, complexity, uncertainty, and conflict. At the same time, he suggested that all collative variables probably involve conflict. Additionally, he considered three variables supplementary to novelty, namely change, surprisingness, and incongruity. Finally, curiosity may not only be aroused by the perception of some stimulus associated with the aforementioned variables ("specific exploration"), but also by a lack of stimulation, out of “boredom” ("diversive exploration").

Curiosity-driven behavior

Curiosity-driven behavior is often defined as behavior through which knowledge is gained, and should therefore encompass all behaviors that provide access to or increase sensory information. Berlyne divided curiosity-driven behavior into three categories; namely, orienting responses, locomotor exploration, and investigatory responses, or, investigatory manipulation. Previously, Berlyne had already suggested that curiosity also includes verbal activities, such as asking questions, and symbolic activities, consisting of internally fueled mental processes such as thinking ("epistemic exploration").

Theories

Like other desires and need states that take on an appetitive quality (e.g. food), curiosity is linked with exploratory behavior and experiences of reward. Curiosity can be described as positive emotions and acquiring knowledge; when one's curiosity has been aroused it is considered inherently rewarding and pleasurable. Discovering new information may also be rewarding because it can help reduce undesirable states of uncertainty rather than stimulating interest. Theories have arisen in attempts to further understand this need to rectify states of uncertainty and the desire to participate in pleasurable experiences of exploratory behaviors.

Curiosity-drive theory

Curiosity-drive theory relates to the undesirable experiences of "uncertainty". The reduction of these unpleasant feelings, in turn, is rewarding. This theory suggests that people desire coherence and understanding in their thought processes. When this coherence is disrupted by something that is unfamiliar, uncertain, or ambiguous, it is curiosity-drive that attempts to gather information and knowledge of the unfamiliar to restore coherent thought processes. Through this theory, the general concept dictates that curiosity is developed strictly out of the desire to make sense of unfamiliar aspects of one's environment through interaction of exploratory behaviors. Once understanding of the unfamiliar has been achieved and coherence has been restored, these behaviors and desires will subside.

Subsets of curiosity-drive theory differ on whether curiosity is a primary or secondary drive and if this curiosity-drive is originated due to one's need to make sense of and regulate their environment or if it is caused by an external stimulus. Causes can range from basic needs that need to be satisfied (e.g. hunger, thirst) to needs in fear induced situations. Each of these subset theories state that whether the need is primary or secondary curiosity is developed from experiences that create a sensation of uncertainty or perceived unpleasantness. Curiosity then acts as a means in which to dispel this uncertainty. By exhibiting curious and exploratory behavior, one is able to gain knowledge of the unfamiliar and thus reduce the state of uncertainty or unpleasantness. This theory, however, does not address the idea that curiosity can often be displayed even in the absence of new or unfamiliar situations. This type of exploratory behavior is common in many species. Take the example of a human toddler who, if bored in his current situation devoid of arousing stimuli, will walk about until something interesting is found. The observation of curiosity even in the absence of novel stimuli pinpoints one of the major shortcomings in the curiosity-drive model.

Optimal-arousal theory

Optimal-arousal theory developed out of the need to explain the desire for some to seek out opportunities to engage in exploratory behaviors without the presence of uncertain or ambiguous situations. Optimal-arousal theory attempts to explain this aspect of curiosity by suggesting that one can be motivated to maintain a pleasurable sense of arousal through these exploratory behaviors.

The concept of optimal-arousal of curiosity suggests that there is a tendency to maintain an optimal level of arousal. When a stimulus is encountered that is associated with complexity, uncertainty, conflict, or novelty, this will increase arousal, and exploratory behavior is employed to learn about that stimulus and thereby reduce arousal again. In contrast, if the environment is boring and lacks excitement, arousal is reduced and exploratory behavior will be engaged in order to increase information input and stimulation, and thereby increasing arousal again. This theory addresses both curiosity elicited by uncertain or unfamiliar situations and curiosity elicited in the absence of such situations.

Cognitive-consistency theory

Cognitive-consistency theories assume that "when two or more simultaneously active cognitive structures are logically inconsistent, arousal is increased, which activates processes with the expected consequence of increasing consistency and decreasing arousal." Similar to optimal-arousal theory, cognitive-consistency theory suggests that there is a tendency to maintain arousal at a preferred, or expected, level, but it also explicitly links the amount of arousal to the amount of experienced inconsistency between an expected situation and the actually perceived situation. When this inconsistency is small, exploratory behavior triggered by curiosity is employed to gather information with which expectancy can be updated through learning to match perception, thereby reducing inconsistency. This approach puts curiosity in a broader perspective, also involving aggression and fear. That is, if the inconsistency is larger, fear or aggressive behavior may be employed to alter the perception in order to make it match expectancy, depending on the size of the inconsistency as well as the specific context. Aggressive behavior is assumed to alter perception by forcefully manipulating it into matching the expected situation, while uninhibited fear results in fleeing, thereby removing the inconsistent stimulus from the perceptual field and resolving the inconsistency.

Integration of the reward pathway into theory

Taking into account the shortcomings of both curiosity-drive and optimal-arousal theories, attempts have been made to integrate neurobiological aspects of reward, wanting, and pleasure into a more comprehensive theory for curiosity. Research suggests that the act of wanting and desiring new information directly involves mesolimbic pathways of the brain that directly account for dopamine activation. The use of these pathways and dopamine activation may account for the assigning of value to new information and then interpreting as reward. This aspect of neurobiology can accompany curiosity-drive theory in motivating exploratory behavior.

Role of neurological aspects and structures

Although the phenomenon of curiosity is widely regarded, its root causes are relatively unknown beyond theory. However, recent studies have provided some insight into the neurological mechanisms that make up what is known as the reward pathway which may impact characteristics associated with curiosity, such as learning, memory, and motivation. Due to the complex nature of curiosity, research that focuses on specific neural processes with these characteristics can help create a better understanding the phenomenon of curiosity as a whole. The following are characteristics of curiosity and their links to neural aspects that can be thought of as essential in creating exploratory behaviors.

Motivation and reward

Dopamine Pathway in the Brain

The drive to learn new information or perform some action is often initiated by the anticipation of reward. In this way, the concepts of motivation and reward are naturally tied to the notion of curiosity.

This idea of reward is defined as the positive reinforcement of an action that encourages a particular behavior by using the emotional sensations of relief, pleasure, and satisfaction that correlate with happiness. Many areas in the brain are used to process reward and come together to form what is called the reward pathway. In this pathway many neurotransmitters play a role in the activation of the reward sensation, including dopamine, serotonin and opioid chemicals.

Dopamine is linked to the process of curiosity, as it is responsible for assigning and retaining reward values of information gained. Research suggests higher amounts of dopamine is released when the reward is unknown and the stimulus is unfamiliar, compared to activation of dopamine when stimulus is familiar.

Nucleus accumbens

The nucleus accumbens is a formation of neurons and is important in reward pathway activation. As previously mentioned, the reward pathway is an integral part in the induction of curiosity. The release of dopamine in investigating response to novel or exciting stimuli. The fast dopamine release observed during childhood and adolescence is important in development, as curiosity and exploratory behavior are the largest facilitators of learning during early years.

In addition, the sensation pleasure of "liking" can occur when opioids are released by nucleus accumbens. This helps someone evaluate the unfamiliar situation or environment and attach value to the novel object. These processes of both wanting and liking play a role in activating the reward system of the brain, and perhaps in the stimulation of curious or information-seeking tendencies as well.

Caudate nucleus

The caudate nucleus, is a region of the brain that is highly responsive to dopamine. The caudate nucleus is another component of the reward pathway. Research has suggested the role of the caudate nucleus anticipates the possibility of and is in anticipation of reward of exploratory behavior and gathered information, thus contributing to factors of curiosity.

Anterior cortices

Regions of the anterior cortices correspond to both conflict and arousal and, as such, seem to reinforce certain exploratory models of curiosity.

Cortisol

Cortisol is a chemical known for its role in stress regulation. However, cortisol may also be associated with curious or exploratory behavior. Findings in recent studies suggesting the role of cortisol with curiosity support the idea of optimal arousal theory. It is suggested the release of a small amount cortisol causing stress encourages curious behavior, while too much stress can initiate a "back away" response.

Attention

Attention is important to the understanding of curiosity because it directly correlates with one's abilities to selectively focus and concentrate on particular stimuli in the surrounding environment. As there are limited cognitive and sensory resources to understand and evaluate various stimuli, attention allows the brain to better focus on what it perceives to be the most important or relevant of these stimuli. Individuals tend to focus their energies on stimuli that are particularly stimulating or engaging. Indicating that the more attention a stimulus garners, the more frequent one's energy and focus will be directed towards that stimulus. This idea suggests an individual will focus their attention on new or unfamiliar stimuli in an effort to better understand or make sense of the unknown over the more familiar or repetitive stimuli, creating the idea that curiosity demands attention.

Striatum

The striatum is a part of the brain which coordinates motivation with body movement. It would seem natural that the striatum plays a role in attention and reward anticipation, both of which are important in the provocation of curiosity.

Precuneus

The precuneus is a region of the brain that is involved in attention, episodic memory, and visuospatial processing. There has been a correlation found between the amount of grey matter in the precuneus and levels of curious and exploratory behaviors; suggesting that the precuneus density has an influence on levels of curiosity.

Memory and learning

Memory plays an important role in the understanding of curiosity. If curiosity is the desire to seek out and understand unfamiliar or novel stimuli, one's memory is important in determining if the stimuli is indeed unfamiliar.

Memory is the process by which the brain can store and access information. In order to determine if the stimulus is novel, an individual must remember if the stimulus has been encountered before. Thus, memory plays an integral role in dictating the level of novelty or unfamiliarity, and the level of need for curiosity.

It can also be suggested that curiosity can affect memory. As previously mentioned, stimuli that are novel tend to capture more of our attention. Additionally, novel stimuli usually have a reward value associated with them, the anticipated reward of what learning that new information may bring. With stronger associations and more attention devoted to a stimulus, it is probable that the memory formed from that stimulus will be longer lasting and easier to recall, both of which facilitate better learning.

Hippocampus and the parahippocampal gyrus

The hippocampus is important in memory formation and recall and therefore instrumental in determining the novelty of various stimuli. Research suggests the hippocampus is involved in generating the underlying motivation to explore for the purpose of learning.

The parahippocampal gyrus (PHG), the area of grey matter surrounding the hippocampus, has recently been implicated in the process of curiosity. This finding suggests that the PHG may be involved in the amplification of curiosity more so than the primary induction of curiosity.

Amygdala

The amygdala often is associated with emotional processing, particularly for the emotion of fear, as well as memory. It is suggested the amygdala is important in processing emotional reactions towards novel or unexpected stimuli and the induction of exploratory behavior. This implies a potential connection between curiosity levels and the amygdala. However, more research is needed on direct correlation.

Early development

Jean Piaget is considered to be the most influential child researcher. He argued that babies and children are constantly trying to make sense of their reality and that it contributed to their intellectual development. According to Piaget, children develop hypotheses, conduct experiments and then reassess their hypotheses depending on what they observe. Piaget was the first to closely document children's actions and interpret them as consistent, calculated effort to test and learn about their environment.

There is no universally accepted definition for curiosity in children. Most research on curiosity has been focused on adults and which typically used self-report measures are inappropriate and inapplicable for studying children. Curiosity is mostly thought of as attributable to a mature person and is characterized in young children as a fledgling feature of their outlook on the world.

Exploratory behaviour is commonly observed in children and is associated with their curiosity development. Several studies look at children's curiosity by simply observing their interaction with novel and familiar toys.

There has been evidence found of a relationship between the anxiety children might feel and their curiosity. One study found that object curiosity in 11-year-olds was negatively related to psychological maladjusted so children who exhibit more anxiety in classroom settings engaged in less curious behaviour. It has also been suggested that certain aspects of classroom learning is dependent on curiosity which can be affected by students' anxiety.

Other measures of childhood curiosity have used exploratory behaviour as a basis but differing on how which parts of this behaviour is best to focus on. Some studies have examined children's preference for complexity/the unknown as a basis for their curiosity measure; others have relied on novelty preference as their basis.

Researchers have also looked at the relationship between a child's reaction to surprise and curiosity. It has been suggested that children are further motivated to learn when dealing with uncertainty. It is argued that their reactions to not having their expectations met would fuel their curiosity more than the introduction of a novel or complex object would.

Ethicality

There is a widely held belief that children's curiosity becomes discouraged throughout the process of formal education: "Children are born scientists. From the first ball they send flying to the ant they watch carry a crumb, children use science's tools—enthusiasm, hypotheses, tests, conclusions—to uncover the world's mysteries. But somehow students seem to lose what once came naturally." 

Sir Ken Robinson discusses a similar phenomenon in his TED Talk titled "Do schools kill creativity?" When curiosity in young people leads to knowledge-gathering it is widely seen as a positive.

Impact from disease

Left: normal brain. Right: AD afflicted brain. Severe degeneration of areas implicated in curiosity

Different neurodegenerative diseases or other psychological disorders can affect various characteristics of curiosity, for instance Alzheimer's disease's effects on memory or depression on motivation and reward. Alzheimer's is a neurodegenerative disease that directly affects the capability and capacity for memory. Depression is a mood disorder that is characterized by a lack of interest in one's environment and feelings of sadness or hopelessness. A lack of curiosity for novel stimuli might also be used as a potential predictor for these and other illnesses.

Morbid curiosity

A crowd mills around the site of a car accident in Czechoslovakia in 1980.

Morbid curiosity exemplifies an aspect of curiosity that can be seen as focused on objects of death, violence, or any other event that may cause harm physically or emotionally.

The idea of morbid curiosity typically is described as having an addictive quality. This addictive aspect of the need to understand or make sense of topics that surround harm, violence or death can be attributed to the idea of one's need to relate unusual and often difficult circumstances to a primary emotion or experience of their own, described as meta-emotions.

Understanding these difficult circumstances dates back to Aristotle in his Poetics, stating, "We enjoy and admire paintings of objects that in themselves would annoy or disgust us."

State and trait curiosity

There are two distinct classifications of types of curiosity: state and trait curiosity. Both types determine whether curiosity comes from within or outside of a person. State curiosity is external such as wondering why things happen for the sake of just curiousness, for example, wondering why most stores open at 8 a.m. This type of curiosity tends to be the most relatable for people on a day-to-day basis since state curiosity relates to high levels of reward. On the other hand, trait curiosity relates to people who are interested in learning. Generally, it could be trying out a new sport or food, or traveling to a new unknown place. One can look at curiosity as the urge that draws people out of their comfort zones and fears as the agent that keeps them within those zones.

Curiosity in artificial intelligence

AI agents are able to display curiosity, and curiosity in AI can be useful for improving the success of an AI agent at various tasks. In artificial intelligence, curiosity is typically defined quantitatively, as the uncertainty the agent has in predicting its own actions given its current state.

In 2019, a study trained AI agent to play video games, but they were rewarded only for curiosity. The agents reliably learned advantageous game behaviors based solely on the curiosity reward.

Suffering

From Wikipedia, the free encyclopedia

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

Tragic mask on the façade of the Royal Dramatic Theatre in Stockholm, Sweden.

Emotions
Acceptance Affection Amusement Anger Angst Anguish Annoyance Anticipation Anxiety Apathy Arousal Awe Boredom Confidence Contempt Contentment Courage Curiosity Depression Desire Disappointment Disgust Distrust Doubt Ecstasy Embarrassment Empathy Enthusiasm Envy Euphoria Faith Fear Frustration Gratification Gratitude Greed Grief Guilt Happiness Hatred Hope Horror Hostility Humiliation Interest Jealousy Joy Kindness Loneliness Love Lust Nostalgia Outrage Panic Passion Pity Pleasure Pride Rage Regret Rejection Remorse Resentment Sadness Self-pity Shame Shock Shyness Social connection Sorrow Suffering Surprise Trust Wonder Worry

Suffering, or pain in a broad sense, may be an experience of unpleasantness and aversion associated with the perception of harm or threat of harm in an individual. Suffering is the basic element that makes up the negative valence of affective phenomena. The opposite of suffering is pleasure or happiness.

Suffering is often categorized as physical or mental. It may come in all degrees of intensity, from mild to intolerable. Factors of duration and frequency of occurrence usually compound that of intensity. Attitudes toward suffering may vary widely, in the sufferer or other people, according to how much it is regarded as avoidable or unavoidable, useful or useless, deserved or undeserved.

Suffering occurs in the lives of sentient beings in numerous manners, often dramatically. As a result, many fields of human activity are concerned with some aspects of suffering. These aspects may include the nature of suffering, its processes, its origin and causes, its meaning and significance, its related personal, social, and cultural behaviors, its remedies, management, and uses.

Terminology

The word suffering is sometimes used in the narrow sense of physical pain, but more often it refers to psychological pain, or more often yet it refers to pain in the broad sense, i.e. to any unpleasant feeling, emotion or sensation. The word pain usually refers to physical pain, but it is also a common synonym of suffering. The words pain and suffering are often used both together in different ways. For instance, they may be used as interchangeable synonyms. Or they may be used in 'contradistinction' to one another, as in "pain is physical, suffering is mental", or "pain is inevitable, suffering is optional". Or they may be used to define each other, as in "pain is physical suffering", or "suffering is severe physical or mental pain".

Qualifiers, such as physical, mental, emotional, and psychological, are often used to refer to certain types of pain or suffering. In particular, mental pain (or suffering) may be used in relationship with physical pain (or suffering) for distinguishing between two wide categories of pain or suffering. A first caveat concerning such a distinction is that it uses physical pain in a sense that normally includes not only the 'typical sensory experience of physical pain' but also other unpleasant bodily experiences including air hunger, hunger, vestibular suffering, nausea, sleep deprivation, and itching. A second caveat is that the terms physical or mental should not be taken too literally: physical pain or suffering, as a matter of fact, happens through conscious minds and involves emotional aspects, while mental pain or suffering happens through physical brains and, being an emotion, involves important physiological aspects.

The word unpleasantness, which some people use as a synonym of suffering or pain in the broad sense, may refer to the basic affective dimension of pain (its suffering aspect), usually in contrast with the sensory dimension, as for instance in this sentence: "Pain-unpleasantness is often, though not always, closely linked to both the intensity and unique qualities of the painful sensation." Other current words that have a definition with some similarity to suffering include distress, unhappiness, misery, affliction, woe, ill, discomfort, displeasure, disagreeableness.

Philosophy

Ancient Greek philosophy

Many of the Hellenistic philosophies addressed suffering.

In Cynicism (philosophy) suffering is alleviated by achieving mental clarity or lucidity (ἁτυφια) (literally "freedom from smoke (τύφος)" which signified false belief, mindlessness, folly, and conceit), developing self-sufficiency (αὐτάρκεια), equanimity, arete, love of humanity, parrhesia, and indifference to the vicissitudes of life (adiaphora ἁδιαφορία).

For Pyrrhonism, suffering comes from dogmas (i.e. beliefs regarding non-evident matters), most particularly beliefs that certain things are either good or bad by nature. Suffering can be removed by developing epoche (suspension of judgment) regarding beliefs, which leads to ataraxia (mental tranquility).

Epicurus (contrary to common misperceptions of his doctrine) advocated that we should first seek to avoid suffering (aponia) and that the greatest pleasure lies in ataraxia, free from the worrisome pursuit or the unwelcome consequences of ephemeral pleasures. Epicureanism's version of Hedonism, as an ethical theory, claims that good and bad consist ultimately in pleasure and pain.

For Stoicism, the greatest good lies in reason and virtue, but the soul best reaches it through a kind of indifference (apatheia) to pleasure and pain: as a consequence, this doctrine has become identified with stern self-control in regard to suffering.

Jeremy Bentham developed hedonistic utilitarianism, a popular doctrine in ethics, politics, and economics. Bentham argued that the right act or policy was that which would cause "the greatest happiness of the greatest number". He suggested a procedure called hedonic or felicific calculus, for determining how much pleasure and pain would result from any action. John Stuart Mill improved and promoted the doctrine of hedonistic utilitarianism. Karl Popper, in The Open Society and Its Enemies, proposed a negative utilitarianism, which prioritizes the reduction of suffering over the enhancement of happiness when speaking of utility: "I believe that there is, from the ethical point of view, no symmetry between suffering and happiness, or between pain and pleasure. (...) human suffering makes a direct moral appeal for help, while there is no similar call to increase the happiness of a man who is doing well anyway." David Pearce, for his part, advocates a utilitarianism that aims straightforwardly at the abolition of suffering through the use of biotechnology (see more details below in section Biology, neurology, psychology). Another aspect worthy of mention here is that many utilitarians since Bentham hold that the moral status of a being comes from its ability to feel pleasure and pain: therefore, moral agents should consider not only the interests of human beings but also those of (other) animals. Richard Ryder came to the same conclusion in his concepts of 'speciesism' and 'painism'. Peter Singer's writings, especially the book Animal Liberation, represent the leading edge of this kind of utilitarianism for animals as well as for people.

Another doctrine related to the relief of suffering is humanitarianism (see also humanitarian principles, humanitarian aid, and humane society). "Where humanitarian efforts seek a positive addition to the happiness of sentient beings, it is to make the unhappy happy rather than the happy happier. (...) [Humanitarianism] is an ingredient in many social attitudes; in the modern world it has so penetrated into diverse movements (...) that it can hardly be said to exist in itself."

Pessimists hold this world to be mainly bad, or even the worst possible, plagued with, among other things, unbearable and unstoppable suffering. Some identify suffering as the nature of the world and conclude that it would be better if life did not exist at all. Arthur Schopenhauer recommends us to take refuge in things like art, philosophy, loss of the will to live, and tolerance toward 'fellow-sufferers'.

Friedrich Nietzsche, first influenced by Schopenhauer, developed afterward quite another attitude, arguing that the suffering of life is productive, exalting the will to power, despising weak compassion or pity, and recommending us to embrace willfully the 'eternal return' of the greatest sufferings.

Philosophy of pain is a philosophical speciality that focuses on physical pain and is, through that, relevant to suffering in general.

Religion

Mahaviratorch-bearer of ahimsa

Suffering plays an important role in a number of religions, regarding matters such as the following: consolation or relief; moral conduct (do no harm, help the afflicted, show compassion); spiritual advancement through life hardships or through self-imposed trials (mortification of the flesh, penance, asceticism); ultimate destiny (salvation, damnation, hell). Theodicy deals with the problem of evil, which is the difficulty of reconciling the existence of an omnipotent and benevolent god with the existence of evil: a quintessential form of evil, for many people, is extreme suffering, especially in innocent children, or in creatures destined to an eternity of torments (see problem of hell).

The 'Four Noble Truths' of Buddhism are about dukkha, a term often translated as suffering. They state the nature of suffering, its cause, its cessation, and the way leading to its cessation, the Noble Eightfold Path. Buddhism considers liberation from dukkha and the practice of compassion (karuna) as basic for leading a holy life and attaining nirvana.

Hinduism holds that suffering follows naturally from personal negative behaviors in one's current life or in a past life (see karma in Hinduism). One must accept suffering as a just consequence and as an opportunity for spiritual progress. Thus the soul or true self, which is eternally free of any suffering, may come to manifest itself in the person, who then achieves liberation (moksha). Abstinence from causing pain or harm to other beings, called ahimsa, is a central tenet of Hinduism, and even more so of another Indian religion, Jainism.

In Judaism, suffering is often seen as a punishment for sins and a test of a person's faith, like the Book of Job illustrates.

For Christianity, redemptive suffering is the belief that human suffering, when accepted and offered up in union with the Passion of Jesus, can remit the just punishment for sins and allow to grow in the love of God, others and oneself.

In Islam, the faithful must endure suffering with hope and faith, not resist or ask why, accept it as Allah's will and submit to it as a test of faith. Allah never asks more than can be endured. One must also work to alleviate the suffering of others, as well as one's own. Suffering is also seen as a blessing. Through that gift, the sufferer remembers God and connects with him. Suffering expunges the sins of human beings and cleanses their soul for the immense reward of the afterlife, and the avoidance of hell.

According to the Bahá'í Faith, all suffering is a brief and temporary manifestation of physical life, whose source is the material aspects of physical existence, and often attachment to them, whereas only joy exists in the spiritual worlds.

Arts and literature

Landscape with the Fall of Icarusby Pieter Brueghel the Elder

Artistic and literary works often engage with suffering, sometimes at great cost to their creators or performers. The Literature, Arts, and Medicine Database offers a list of such works under the categories art, film, literature, and theater. Be it in the tragic, comic or other genres, art and literature offer means to alleviate (and perhaps also exacerbate) suffering, as argued for instance in Harold Schweizer's Suffering and the remedy of art.

This Brueghel painting is among those that inspired W. H. Auden's poem Musée des Beaux Arts:

About suffering they were never wrong,
The Old Masters; how well, they understood
Its human position; how it takes place
While someone else is eating or opening a window or just walking dully along;
(...)
In Breughel's Icarus, for instance: how everything turns away
Quite leisurely from the disaster; (...)

Social sciences

Social suffering, according to Arthur Kleinman and others, describes "collective and individual human suffering associated with life conditions shaped by powerful social forces". Such suffering is an increasing concern in medical anthropology, ethnography, mass media analysis, and Holocaust studies, says Iain Wilkinson, who is developing a sociology of suffering.

The Encyclopedia of World Problems and Human Potential is a work by the Union of International Associations. Its main databases are about world problems (56,564 profiles), global strategies and solutions (32,547 profiles), human values (3,257 profiles), and human development (4,817 profiles). It states that "the most fundamental entry common to the core parts is that of pain (or suffering)" and "common to the core parts is the learning dimension of new understanding or insight in response to suffering".

Ralph G.H. Siu, an American author, urged in 1988 the "creation of a new and vigorous academic discipline, called panetics, to be devoted to the study of the infliction of suffering", The International Society for Panetics was founded in 1991 to study and develop ways to reduce the infliction of human suffering by individuals acting through professions, corporations, governments, and other social groups.

In economics, the following notions relate not only to the matters suggested by their positive appellations, but to the matter of suffering as well: Well-being or Quality of life, Welfare economics, Happiness economics, Gross National Happiness, Genuine Progress Indicator.

In law, "Pain and suffering" is a legal term that refers to the mental distress or physical pain endured by a plaintiff as a result of injury for which the plaintiff seeks redress. Assessments of pain and suffering are required to be made for attributing legal awards. In the Western world these are typical made by juries in a discretionary fashion and are regarded as subjective, variable, and difficult to predict, for instance in the US, UK, Australia, and New Zealand.

In management and organization studies, drawing on the work of Eric Cassell, suffering has been defined as the distress a person experiences when they perceive a threat to any aspect of their continued existence, whether physical, psychological, or social. Other researchers have noted that suffering results from an inability to control actions that usually define one's view of one's self and that the characteristics of suffering include the loss of autonomy, or the loss of valued relationships or sense of self. Suffering is therefore determined not by the threat itself but, rather, by its meaning to the individual and the threat to their personhood.

Biology, neurology, psychology

Suffering and pleasure are respectively the negative and positive affects, or hedonic tones, or valences that psychologists often identify as basic in our emotional lives. The evolutionary role of physical and mental suffering, through natural selection, is primordial: it warns of threats, motivates coping (fight or flight, escapism), and reinforces negatively certain behaviors (see punishment, aversives). Despite its initial disrupting nature, suffering contributes to the organization of meaning in an individual's world and psyche. In turn, meaning determines how individuals or societies experience and deal with suffering.

Neuroimaging sheds light on the seat of suffering

Many brain structures and physiological processes are involved in suffering (particularly the anterior insula and cingulate cortex, both implicated in nociceptive and empathic pain). Various hypotheses try to account for the experience of suffering. One of these, the pain overlap theory takes note, thanks to neuroimaging studies, that the cingulate cortex fires up when the brain feels suffering from experimentally induced social distress or physical pain as well. The theory proposes therefore that physical pain and social pain (i.e. two radically differing kinds of suffering) share a common phenomenological and neurological basis.

According to David Pearce’s online manifesto "The Hedonistic Imperative," suffering is the avoidable result of Darwinian genetic design. Pearce promotes replacing the pain/pleasure axis with a robot-like response to noxious stimuli or with gradients of bliss, through genetic engineering and other technical scientific advances.

Hedonistic psychology, affective science, and affective neuroscience are some of the emerging scientific fields that could in the coming years focus their attention on the phenomenon of suffering.

Health care

Disease and injury may contribute to suffering in humans and animals. For example, suffering may be a feature of mental or physical illness such as borderline personality disorder and occasionally in advanced cancer. Health care addresses this suffering in many ways, in subfields such as medicine, clinical psychology, psychotherapy, alternative medicine, hygiene, public health, and through various health care providers.

However..."If people feel unhappy when burdened by negative life events, this is no mental disorder, but “healthy suffering” . It is of great importance not to medicalize such everyday problems."

Health care approaches to suffering, however, remain problematic. Physician and author Eric Cassell, widely cited on the subject of attending to the suffering person as a primary goal of medicine, has defined suffering as "the state of severe distress associated with events that threaten the intactness of the person". Cassell writes: "The obligation of physicians to relieve human suffering stretches back to antiquity. Despite this fact, little attention is explicitly given to the problem of suffering in medical education, research or practice." Mirroring the traditional body and mind dichotomy that underlies its teaching and practice, medicine strongly distinguishes pain from suffering, and most attention goes to the treatment of pain. Nevertheless, physical pain itself still lacks adequate attention from the medical community, according to numerous reports. Besides, some medical fields like palliative care, pain management (or pain medicine), oncology, or psychiatry, do somewhat address suffering 'as such'. In palliative care, for instance, pioneer Cicely Saunders created the concept of 'total pain' ('total suffering' say now the textbooks), which encompasses the whole set of physical and mental distress, discomfort, symptoms, problems, or needs that a patient may experience hurtfully.

Relief and prevention in society

Since suffering is such a universal motivating experience, people, when asked, can relate their activities to its relief and prevention. Farmers, for instance, may claim that they prevent famine, artists may say that they take our minds off our worries, and teachers may hold that they hand down tools for coping with life hazards. In certain aspects of collective life, however, suffering is more readily an explicit concern by itself. Such aspects may include public health, human rights, humanitarian aid, disaster relief, philanthropy, economic aid, social services, insurance, and animal welfare. To these can be added the aspects of security and safety, which relate to precautionary measures taken by individuals or families, to interventions by the military, the police, the firefighters, and to notions or fields like social security, environmental security, and human security.

The nongovernmental research organization Center on Long-Term Risk, formerly known as the Foundational Research Institute, focuses on reducing risks of astronomical suffering (s-risks) from emerging technologies. Another organization also focused on research, the Center on Reducing Suffering, has a similar focus, with a stress on clarifying what priorities there should be at a practical level to attain the goal of reducing intense suffering in the future.

Uses

Philosopher Leonard Katz wrote: "But Nature, as we now know, regards ultimately only fitness and not our happiness (...), and does not scruple to use hate, fear, punishment and even war alongside affection in ordering social groups and selecting among them, just as she uses pain as well as pleasure to get us to feed, water and protect our bodies and also in forging our social bonds."

People make use of suffering for specific social or personal purposes in many areas of human life, as can be seen in the following instances:

• In arts, literature, or entertainment, people may use suffering for creation, for performance, or for enjoyment. Entertainment particularly makes use of suffering in blood sports and violence in the media, including violent video games depiction of suffering. A more or less great amount of suffering is involved in body art. The most common forms of body art include tattooing, body piercing, scarification, human branding. Another form of body art is a sub-category of performance art, in which for instance the body is mutilated or pushed to its physical limits.
• In business and various organizations, suffering may be used for constraining humans or animals into required behaviors.
• In a criminal context, people may use suffering for coercion, revenge, or pleasure.
• In interpersonal relationships, especially in places like families, schools, or workplaces, suffering is used for various motives, particularly under the form of abuse and punishment. In another fashion related to interpersonal relationships, the sick, or victims, or malingerers, may use suffering more or less voluntarily to get primary, secondary, or tertiary gain.
• In law, suffering is used for punishment; victims may refer to what legal texts call "pain and suffering" to get compensation; lawyers may use a victim's suffering as an argument against the accused; an accused's or defendant's suffering may be an argument in their favor; authorities at times use light or heavy torture in order to get information or a confession.
• In the news media, suffering is often the raw material.
• In personal conduct, people may use suffering for themselves, in a positive way. Personal suffering may lead, if bitterness, depression, or spitefulness is avoided, to character-building, spiritual growth, or moral achievement; realizing the extent or gravity of suffering in the world may motivate one to relieve it and may give an inspiring direction to one's life. Alternatively, people may make self-detrimental use of suffering. Some may be caught in compulsive reenactment of painful feelings in order to protect them from seeing that those feelings have their origin in unmentionable past experiences; some may addictively indulge in disagreeable emotions like fear, anger, or jealousy, in order to enjoy pleasant feelings of arousal or release that often accompany these emotions; some may engage in acts of self-harm aimed at relieving otherwise unbearable states of mind.
• In politics, there is purposeful infliction of suffering in war, torture, and terrorism; people may use nonphysical suffering against competitors in nonviolent power struggles; people who argue for a policy may put forward the need to relieve, prevent or avenge suffering; individuals or groups may use past suffering as a political lever in their favor.
• In religion, suffering is used especially to grow spiritually, to expiate, to inspire compassion and help, to frighten, to punish.
• In rites of passage, rituals that make use of suffering are frequent.
• In science, humans and animals are subjected on purpose to aversive experiences for the study of suffering or other phenomena.
• In sex, especially in a context of sadism and masochism or BDSM, individuals may use a certain amount of physical or mental suffering (e.g. pain, humiliation).
• In sports, suffering may be used to outperform competitors or oneself; see sports injury, and no pain, no gain; see also blood sport and violence in sport as instances of pain-based entertainment.