Activity-dependent plasticity is a form of functional and structural neuroplasticity that arises from the use of cognitive functions and personal experience; hence, it is the biological basis for learning and the formation of new memories. Activity-dependent plasticity is a form of neuroplasticity that arises from intrinsic or endogenous activity, as opposed to forms of neuroplasticity that arise from extrinsic or exogenous factors, such as electrical brain stimulation- or drug-induced neuroplasticity. The brain's
ability to remodel itself forms the basis of the brain's capacity to
retain memories, improve motor function, and enhance comprehension and
speech amongst other things. It is this trait to retain and form
memories that is associated with neural plasticity and therefore many of
the functions individuals perform on a daily basis. This plasticity occurs as a result of changes in gene expression which are triggered by signaling cascades that are activated by various signaling molecules (e.g., calcium, dopamine, and glutamate, among many others) during increased neuronal activity.
The brain's ability to adapt toward active functions allows
humans to specialize in specific processes based on relative use and
activity. For example, a right-handed person may perform any movement
poorly with their left hand but continuous practice with the
non-dominant hand can cause one to become ambidextrous. Another example is if someone was born with a neurological disorder such as autism or had a stroke
that resulted in a disorder, then they are capable of retrieving much
of their lost function through practice, which in turn "rewires" the
brain to mitigate neurological dysfunction.
History
The idea of neural plasticity was first proposed during 1890 by William James in Principles of Psychology.
During the first half of the 1900s, the word 'plasticity' was directly
and indirectly rejected throughout science. Many scientists found it
hard to receive funding because nearly everyone unanimously supported
the fact that the brain was fully developed at adulthood and specific
regions were unable to change functions after the critical period. It was believed that each region of the brain
had a set and specific function. Despite this, several pioneers pushed
the idea of plasticity through means of various experiments and
research. There are others that helped to the current progress of
activity-dependent plasticity but the following contributed very
effective results and ideas early on.
Pioneers of activity-dependent plasticity
The history of activity-dependent plasticity begins with Paul Bach y Rita.
With conventional ideology being that the brain development is
finalized upon adulthood, Bach y Rita designed several experiments in
the late 1960s and 1970s that proved that the brain is capable of
changing. These included a pivotal visual substitution method for blind
people provided by tactile image projection in 1969.
The basis behind this experiment was to take one sense and use it to
detect another: in this case use the sense of touch on the tongue to
visualize the surrounding. This experiment was years ahead of its time
and led to many questions and applications. A similar experiment was
reported again by Bach y Rita in 1986 where vibrotactile stimulation was
delivered to the index fingertips of naive blindfolded subjects.
Even though the experiment did not yield great results, it supported
the study and proposed further investigations. In 1998, his design was
even further developed and tested again with a 49-point electrotactile
stimulus array on the tongue.
He found that five sighted adult subjects recognized shapes across all
sizes 79.8% of the time, a remarkable finding that has led to the
incorporation of the tongue electrotactile stimulus into cosmetically
acceptable and practical designs for blind people. In later years, he
has published a number of other articles including "Seeing with the
brain" in 2003 where Bach y Rita addresses the plasticity of the brain
relative to visual learning. Here, images are enhanced and perceived by other plastic mechanisms within the realm of information passing to the brain.
Another pioneer within the field of activity-dependent plasticity is Michael Merzenich,
currently a professor in neuroscience at the University of California,
San Francisco. One of his contributions includes mapping out and
documenting the reorganization of cortical regions after alterations due
to plasticity. While assessing the recorded changes in the primary somatosensory cortex
of adult monkeys, he looked at several features of the data including
how altered schedules of activity from the skin remap to cortical
modeling and other factors that affect the representational remodeling
of the brain. His findings within these studies have since been applied
to youth development and children with language-based learning
impairments. Through many studies involving adaptive training exercises
on computer, he has successfully designed methods to improve their
temporal processing skills. These adaptive measures include
word-processing games and comprehension tests that involve multiple
regions of the brain in order to answer. The results later translated
into his development of the Fast ForWord
program in 1996, which aims to enhance cognitive skills of children
between kindergarten and twelfth grade by focusing on developing
"phonological awareness".
It has proven very successful at helping children with a variety of
cognitive complications. In addition, it has led to in depth studies of
specific complications such as autism and intellectual disability and the causes of them.
Alongside a team of scientists, Merzenich helped to provide evidence
that autism probes monochannel perception where a stronger
stimulus-driven representation dominates behavior and weaker stimuli are
practically ignored in comparison.
Structure of neurons
Diagram displaying components of a myelinated vertebrate motorneuron.
Neurons
are the basic functional unit of the brain and process and transmit
information through signals. Many different types of neurons can be
identified based on their function, such as sensory neurons or motor neurons.
Each responds to specific stimuli and sends respective and appropriate
chemical signals to other neurons. The basic structure of a neuron is
shown here on the right and consists of a nucleus that contains genetic information; the cell body, or the soma, which is equipped with dendritic branches that mostly receive the incoming inputs from other neurons; a long, thin axon that bears axon terminals which carry the output information to other neurons. The dendrites and axons are interfaced through a small connection called a synapse.
This component of the neuron contains a variety of chemical messengers
and proteins that allow for the transmission of information. It is the
variety of proteins and effect of the signal that fundamentally lead to
the plasticity feature.
Structures and molecular pathways involved
Activity-dependent
plasticity of one form or another has been observed in most areas of
the brain. In particular, it is thought that the reorganization of
sensory and motor maps involves a variety of pathways and cellular
structures related to relative activity.
Many molecules have been implicated in synaptic plasticity. Notably, AMPA and NMDA
receptors are key molecules in mechanisms of long and short-term
potentiation between neurons. NMDA receptors can detect local activity
due to activation and therefore modify signaling in the post-synaptic
cell. The increased activity and coordination between pre- and
post-synaptic receptors leads to more permanent changes and therefore
result in plasticity. Hebb's postulate addresses this fact by stating
that synaptic terminals are strengthened by correlated activity and will
therefore sprout new branches. However, terminals that experience
weakened and minimal activity will eventually lose their synaptic
connection and deteriorate.
A major target of all molecular signaling is the inhibitory connections made by GABAergic
neurons. These receptors exist at postsynaptic sites and along with the
regulation of local inhibitory synapses have been found to be very
sensitive to critical period alterations. Any alteration to the
receptors leads to changed concentrations of calcium in the affected cells and can ultimately influence dendritic and axonal branching. This concentration change is the result of many kinases being activated, the byproduct of which may enhance specific gene expression.
Illustration
of the elements incorporated in synaptic transmission. An action
potential is generated and travels down the axon to the axon terminal,
where it is released and provokes a neurotransmitter release that acts
on the post-synaptic end.
In addition, it has been identified that the Wg
postsynaptic pathway, which is responsible for the coding and
production of many molecules for development events, can be
bidirectionally stimulated and is responsible for the downstream
alteration of the postsynaptic
neuron. When the Wg presynaptic pathway is activated, however, it
alters cytoskeletal structure through transcription and translation.
Cell adhesion molecules (CAMs) are also important in plasticity as they help coordinate the signaling across the synapse. More specifically, integrins,
which are receptors for extracellular matrix proteins and involved with
CAMs, are explicitly incorporated in synapse maturation and memory
formation. They play a crucial role in the feedback regulation of
excitatory synaptic strength, or long-term potentiation (LTP), and help to control synaptic strength by regulating AMPA receptors, which result in quick, short synaptic currents.
But, it is the metabotropic glutamate receptor 1 (mGlu1) that has been
discovered to be required for activity-dependent synaptic plasticity in
associative learning.
Activity-dependent plasticity is seen in the primary visual cortex,
a region of the brain that processes visual stimuli and is capable of
modifying the experienced stimuli based on active sensing and arousal
states. It is known that synaptic communication trends between excited
and depressed states relative to the light/dark cycle. By
experimentation on rats, it was found that visual experience during
vigilant states leads to increased responsiveness and plastic changes in
the visual cortex.
More so, depressed states were found to negatively alter the stimulus
so the reaction was not as energetic. This experiment proves that even
the visual cortex is capable of achieving activity-dependent plasticity
as it is reliant on both visual exploration and the arousal state of the
animal.
Role in learning
Activity-dependent
plasticity plays a very important role in learning and in the ability
of understanding new things. It is responsible for helping to adapt an
individual's brain according to the relative amount of usage and
functioning. In essence, it is the brain's ability to retain and develop
memories based on activity-driven changes of synaptic strength that
allow stronger learning of information. It is thought to be the growing
and adapting quality of dendritic spines that provide the basis for synaptic plasticity connected to learning and memory.
Dendritic spines accomplish this by transforming synaptic input into
neuronal output and also by helping to define the relationship between
synapses.
In recent studies, a specific gene has also been identified as
having a strong role in synapse growth and activity-dependent
plasticity: the microRNA 132 gene (miR132).
This gene is regulated by the cAMP response element-binding (CREB)
protein pathway and is capable of enhancing dendritic growth when
activated. The miR132 gene is another component that is responsible for
the brain's plasticity and helps to establish stronger connections
between neurons.
Another plasticity-related gene involved in learning and memory is Arc/Arg3.1. The Arc gene is activity-regulated and the transcribed mRNA is localized to activated synaptic sites where the translated protein plays a role in AMPA receptor trafficking. Arc is a member of a class of proteins called immediate early genes
(IEG) that are rapidly transcribed in response to synaptic input. Of
the estimated 30-40 genes that comprise the total neuronal IEG response,
all are prototypical activity-dependent genes and a number have been
implicated in learning and memory. For example, zif268, Arc, beta-activin, tPA, Homer, and COX-2 have all been implicated in long-term potentiation (LTP), a cellular correlate of learning and memory.
Mechanisms involved
There are a variety of mechanisms involved in activity-dependent plasticity. These include LTP, long-term depression (LTD), synaptic elimination, neurogenesis, and synaptogenesis. The mechanisms of activity-dependent plasticity result in membrane depolarization and calcium influx, which in turn trigger cellular changes that affect synaptic connections and gene transcription. In essence, neuronal activity regulates gene expression related to dendritic branching and synapse development. Mutations
in activity-dependent transcription-related genes can lead to
neurological disorders. Each of the studies' findings aims to help
proper development of the brain while improving a wide variety of tasks
such as speech, movement, comprehension, and memory. More so, the
findings better explain the development induced by plasticity.
It is known that during postnatal life a critical step to nervous
system development is synapse elimination. The changes in synaptic
connections and strength are results from LTP and LTD and are strongly
regulated by the release of brain-derived neurotrophic factor (BDNF), an activity-dependent synapse-development protein. In addition to BDNF, Nogo-66 receptors, and more specifically NgR1, are also involved in the development and regulation of neuronal structure. Damage to this receptor leads to pointless
LTP and attenuation of LTD. Both situations imply that NgR1 is a
regulator of synaptic plasticity. From experiments, it has been found
that stimulation inducing LTD leads to a reduction in synaptic strength
and loss of connections but, when coupled simultaneously with
low-frequency stimulation, helps the restructuring of synaptic contacts.
The implications of this finding include helping people with receptor
damage and providing insight into the mechanism behind LTP.
Another research model of activity-dependent plasticity includes
the excitatory corticostriatal pathway that is involved in information
processing related to adaptive motor behaviors and displays long-lasting
synaptic changes. The change in synaptic strength is responsible for
motor learning and is dependent on the simultaneous activation of
glutamatergic corticostriatal and dopaminergic nigrostriatal pathways.
These are the same pathways affected in Parkinson's disease, and the degeneration of synapses within this disorder may be responsible for the loss of some cognitive abilities.
Relationship to behavior
Intellectual disability
Since
plasticity is such a fundamental property of brain function due to its
involvement in brain development, brain repair, and cognitive processes,
its proper regulation is necessary for normal physiology. Mutations
within any of the genes associated with activity-dependent plasticity
have been found to positively correlate with various degrees of intellectual disability. The two types of intellectual disability
related to plasticity depend on dysfunctional neuronal development or
alterations in molecular mechanisms involved in synaptic organization.
Complications within either of these types can greatly reduce brain
capability and comprehension.
Stroke rehabilitation
On
the other hand, people with such conditions have the capacity to
recover some degree of their lost abilities through continued challenges
and use. An example of this can be seen in Norman Doidge's The Brain That Changes Itself. Bach y Rita's father had a disabling stroke
that left the 65-year-old man half-paralyzed and unable to speak.
After one year of crawling and unusual therapy tactics including playing
basic children's games and washing pots, his father's rehabilitation
was nearly complete and he went back to his role as a professor at City
College in New York.
This remarkable recovery from a stroke proves that even someone with
abnormal behavior and severe medical complications can recover nearly
all of the normal functions by much practice and perseverance.
Recent studies have reported that a specific gene, FMR1, is highly involved in activity-dependent plasticity and fragile X syndrome
(FraX) is the result of this gene's loss of function. The FMR1 gene
produces protein FMRP, which mediates activity-dependent control of
synaptic structure. The loss or absence of this gene almost certainly
leads to both autism and intellectual disability.
Dr. Gatto has found that early introduction of the product FMRP results
in nearly complete restructuring of the synapses. This method is not as
effective, though, when introduced into a mature subject and only
partially accommodates for the losses of FMR1.
The discovery of this gene provides a possible location for
intervention for young children with these abnormalities as this gene
and its product act early to construct synaptic architecture.
Stress
A common issue amongst most people in the United States is high levels of stress
and also disorders associated with continuous stress. Many regions of
the brain are very sensitive to stress and can be damaged with extended
exposure. More importantly, many of the mechanisms involved with
increased memory retention, comprehension,
and adaptation are thought to involve LTP and LTD, two
activity-dependent plasticity mechanisms that stress can directly
suppress. Several experiments have been conducted in order to discover
the specific mechanisms for this suppression and also possible
intervention methods. Dr. Li and several others have actually identified
the TRPV1 channel as a target to facilitate LTP and suppress LTD,
therefore helping to protect the feature of synaptic plasticity and
retention of memory from the effects of stress.
Future studies
The
future studies and questions for activity-dependent plasticity are
nearly endless because the implications of the findings will enable many
treatments. Despite many gains within the field, there are a wide
variety of disorders that further understanding of activity-dependent
mechanisms of plasticity would help treat and perhaps cure. These
include autism, different severities of intellectual disability, schizophrenia, Parkinson's disease, stress, and stroke.
In addition to a better understanding of the various disorders,
neurologists should and will look at the plasticity incurred by the immune system, as it will provide great insight into diseases and also give the basis of new immune-centered therapeutics.
A better perspective of the cellular mechanisms that regulate neuronal
morphology is the next step to discovering new treatments for learning
and memory pathological conditions.
The psychological and physiological effects of meditation have been studied. In recent years, studies of meditation have increasingly involved the use of modern instruments, such as functional magnetic resonance imaging and electroencephalography, which are able to observe brain physiology and neural activity in living subjects, either during the act of meditation itself or before and after meditation. Correlations can thus be established between meditative practices and brain structure or function.
Since the 1950s hundreds of studies on meditation have been
conducted, but many of the early studies were flawed and thus yielded
unreliable results. Another major review article also cautioned about possible misinformation and misinterpretation of data related to the subject.
Contemporary studies have attempted to address many of these flaws with
the hope of guiding current research into a more fruitful path.
However, the question of meditation's place in mental health care
is far from settled and there is no general consensus among experts.
Though meditation is generally deemed useful its superiority has been
challenged in several recent meta-analyses that only show
small-to-moderate effect sizes. This means that meditation is no better
than the standard measures of self-care like sleep, exercise, nutrition
and social intercourse. Importantly, it has a worse safety profile than
these standard measures (see section on adverse-effects).
A recent meta-analysis also indicates that the increased mindfulness
experienced by mental health patients may not be the result of explicit
mindfulness interventions but more of an artefact of their mental health
condition (e.g., depression, anxiety) as it is equally experienced by
the participants that were placed in the control condition (e.g., active
controls, waiting list). This raises further questions as to what
exactly meditation does, if anything, that is significantly different
from the heightened self-monitoring and self-care that follows in the
wake of spontaneous recovery or from the positive effects of
encouragement and care that is usually provided in ordinary health-care
settings (see section on the difficulties studying meditation).
There also seems to be a critical moderation of the effects of
meditation according to individual differences. In one meta-analysis
from 2022, involving a total of 7782 participants, the researchers found
that a higher baseline level of psychopathology (e.g., depression) was
associated with deterioration in mental health after a meditation
intervention, and thus was contraindicated.
Effects of mindfulness meditation
A
previous study commissioned by the US Agency for Healthcare Research
and Quality found that meditation interventions reduce multiple negative
dimensions of psychological stress. Other systematic reviews and meta-analyses show that mindfulness meditation has several mental health benefits such as bringing about reductions in depression symptoms, improvements in mood, stress-resilience and attentional control. Mindfulness interventions also appear to be a promising intervention for managing depression in youth.
Mindfulness meditation is useful for managing stress, anxiety and also appears to be effective in treating substance use disorders.
A recent meta-analysis by Hilton et al. (2016) including 30 randomized
controlled trials found high quality evidence for improvement in
depressive symptoms.
Other review studies have shown that mindfulness meditation can enhance
the psychological functioning of breast cancer survivors, is effective for people with eating disorders and may also be effective in treating psychosis.
Studies have also shown that rumination and worry contribute to mental illnesses such as depression and anxiety, and mindfulness-based interventions are effective in the reduction of worry.Some
studies suggest that mindfulness meditation contributes to a more
coherent and healthy sense of self and identity, when considering
aspects such as sense of responsibility, authenticity, compassion,
self-acceptance and character.
The analgesic effect of mindfulness meditation may involve multiple brain mechanisms, of which, chronic pain is shown to have a small decrease when performing meditation.
Current research demonstrates a lack of high-quality data to support a
strong case for clinical prescription of mediation, however future
research may further change our understanding of chronic pain treatment
and mindfulness, but there are too few studies to allow conclusions about its effects on chronic pain.
The act of mindful meditation creates alterations in the brain that lead to a heightened ability to improve emotions.
In an 8-week mindfulness meditation study, Gotink et al. discovered
that amygdala, insula, cingulate cortex, and hippocampus activity
decreased.
Importantly, these short-term changes are often equated to a brain with
longer time spent doing mindfulness meditation and interventions, such
as months or years. There is a clear benefit for performing mindful
meditation even if for a short duration. Another meta-analysis found
preliminary evidence for effects in the prefrontal cortex and other
brain regions associated with body awareness.
However, these results should be interpreted with caution as funnel
plots indicate that publication bias is an issue in meditation research.
A 2016 review using 78 functional neuroimaging studies suggests that
different meditation styles are associated with different brain
activity. While other studies have found structural changes in the brain may occur, but most studies have utilized weak methodology.
Attention and mindfulness
Attention networks and mindfulness meditation
Psychological and Buddhist conceptualizations of mindfulness
both highlight awareness and attention training as key components, in
which levels of mindfulness can be cultivated with practice of
mindfulness meditation.
Focused attention meditation (FAM) and open monitoring meditation (OMM)
are distinct types of mindfulness meditation; FAM refers to the
practice of intently maintaining focus on one object, whereas OMM is the
progression of general awareness of one's surroundings while regulating
thoughts.
Focused attention meditation is typically practiced first to
increase the ability to enhance attentional stability, and awareness of
mental states with the goal being to transition to open monitoring
meditation practice that emphasizes the ability to monitor
moment-by-moment changes in experience, without a focus of attention to
maintain. Mindfulness meditation may lead to greater cognitive flexibility.
In an active randomized controlled study completed in 2019,
participants who practiced mindfulness meditation demonstrated a greater
improvement in awareness and attention than participants in the active control condition. Alpha waveneural oscillationpower
(which is normally associated with an alert resting state) has been
shown to be increased by mindfulness in both healthy subjects and
patients.
Sustained attention
Tasks of sustained attention
relate to vigilance and the preparedness that aids completing a
particular task goal. Psychological research into the relationship
between mindfulness meditation and the sustained attention network have
revealed the following:
In a continuous performance task an association was found between higher dispositional mindfulness and more stable maintenance of sustained attention.
In an electroencephalography study, the attentional blink effect was reduced, and P3b ERP amplitude decreased in a group of participants who completed a mindfulness retreat. The incidence of reduced attentional blink effect relates to an increase in detectability of a second target.
A greater degree of attentional resources may also be reflected in
faster response times in task performance, as was found for participants
with higher levels of mindfulness experience.
Selective attention
Selective attention as linked with the orientation network, is involved in selecting the relevant stimuli to attend to.
Performance in the ability to limit attention to potentially sensory
inputs (i.e. selective attention) was found to be higher following the
completion of an eight-week MBSR course, compared to a one-month retreat
and control group (with no mindfulness training).
The ANT task is a general applicable task designed to test the three
attention networks, in which participants are required to determine the
direction of a central arrow on a computer screen.
Efficiency in orienting that represent the capacity to selectively
attend to stimuli was calculated by examining changes in the reaction
time that accompanied cues indicating where the target occurred relative
to the aid of no cues.
Meditation experience was found to correlate negatively with reaction times on an Eriksen flanker task
measuring responses to global and local figures. Similar findings have
been observed for correlations between mindfulness experience in an
orienting score of response times taken from Attention Network Task
performance.
Participants who engaged in the Meditation Breath Attention Score
exercise performed better on anagram tasks and reported greater focused
attention on this task compared to those who did not undergo this
exercise.
Executive control attention
Executive
control attention include functions of inhibiting the conscious
processing of distracting information. In the context of mindful
meditation, distracting information relates to attention grabbing mental
events such as thoughts related to the future or past.
More than one study have reported findings of a reduced Stroop effect following mindfulness meditation training.
The Stroop effect indexes interference created by having words printed
in color that differ to the read semantic meaning e.g. green printed in
red. However findings for this task are not consistently found. For instance the MBSR may differ to how mindful one becomes relative to a person who is already high in trait mindfulness.
Using the Attention Network Task (a version of Eriksen flanker task) it was found that error scores that indicate executive control performance were reduced in experienced meditators and following a brief five-session mindfulness training program.
A neuroimaging study supports behavioral research findings that
higher levels of mindfulness are associated with greater proficiency to
inhibit distracting information. As greater activation of the rostral
anterior cingulate cortex (ACC) was shown for mindfulness meditators
than matched controls.
Participants with at least 6 years of experience meditating
performed better on the Stroop Test compared to participants who had not
had experience meditating. The group of meditators also had lower reaction times during this test than the group of non-meditators.
Following a Stroop test, reduced amplitude of the P3
ERP component was found for a meditation group relative to control
participants. This was taken to signify that mindfulness meditation
improves executive control functions of attention. An increased
amplitude in the N2
ERP component was also observed in the mindfulness meditation group,
thought to reflect more efficient perceptual discrimination in earlier
stages of perceptual processing.
Emotion regulation and mindfulness
Research shows meditation practices lead to greater emotional regulation
abilities. Mindfulness can help people become more aware of thoughts in
the present moment, and this increased self-awareness leads to better
processing and control over one's responses to surroundings or
circumstances.
Positive effects of this heightened awareness include a greater
sense of empathy for others, an increase in positive patterns of
thinking, and a reduction in anxiety. Reductions in rumination
also have been found following mindfulness meditation practice,
contributing to the development of positive thinking and emotional
well-being.
Evidence of mindfulness and emotion regulation outcomes
Emotional reactivity can be measured and reflected in brain regions related to the production of emotions.
It can also be reflected in tests of attentional performance, indexed
in poorer performance in attention related tasks. The regulation of
emotional reactivity as initiated by attentional control capacities can
be taxing to performance, as attentional resources are limited.
Patients with social anxiety disorder (SAD) exhibited reduced
amygdala activation in response to negative self-beliefs following an
MBSR intervention program that involves mindfulness meditation practice.
The LPP ERP component indexes arousal and is larger in amplitude for emotionally salient stimuli relative to neutral.
Individuals higher in trait mindfulness showed lower LPP responses to
high arousal unpleasant images. These findings suggest that individuals
with higher trait mindfulness were better able to regulate emotional
reactivity to emotionally evocative stimuli.
Participants who completed a seven-week mindfulness training program
demonstrated a reduction in a measure of emotional interference
(measured as slower responses times following the presentation of
emotional relative to neutral pictures). This suggests a reduction in
emotional interference.
Following a MBSR intervention, decreases in social anxiety symptom
severity were found, as well as increases in bilateral parietal cortex
neural correlates. This is thought to reflect the increased employment
of inhibitory attentional control capacities to regulate emotions.
Participants who engaged in emotion-focus meditation and breathing
meditation exhibited delayed emotional response to negatively valanced
film stimuli compared to participants who did not engage in any type of
meditation.
Controversies in mindful emotion regulation
It is debated as to whether top-down executive control regions such as the dorsolateral prefrontal cortex (DLPFC), are required or not
to inhibit reactivity of the amygdala activation related to the
production of evoked emotional responses. Arguably an initial increase
in activation of executive control regions developed during mindfulness
training may lessen with increasing mindfulness expertise.
Furthermore, current research data is inconclusive and incomplete
in linking positive effects of mindful meditation with a variety of
reported positive effects. Additional high-fidelity studies are needed
before a more complete understanding of the full effects of mindfulness
can be reached.
Stress reduction
Research has shown stress reduction benefits from mindfulness. A 2019 study tested the effects of meditation on the psychological
well-being, work stress, and blood pressure of employees working in the
United Kingdom. One group of participants were instructed to meditate
once a day using a mindfulness app on their smartphones, while the
control group did not engage in meditation. Measurements of well-being,
stress, and perceived workplace support were taken for both groups
before the intervention and then again after four months. Based on
self-report questionnaires, the participants who engaged in meditation
showed a significant increase in psychological well-being and perceived
workplace support. The meditators also reported a significant decrease
in anxiety and stress levels.
Another study conducted to understand association between
mindfulness, perceived stress and work engagement indicated that
mindfulness was associated with lower perceived stress and higher work
engagement.
Other research shows decreased stress levels in people who engage
in meditation after shorter periods of time as well. Evidence of
significant stress reduction was found after only three weeks of
meditation intervention.
Brief, daily meditation sessions can alter one's behavioral response to
stressors, improving coping mechanisms and decreasing the adverse
impact caused by stress.
A study from 2016 examined anxiety and emotional states of naive
meditators before and after a seven-day meditation retreat in Thailand.
Results displayed a significant reduction in perceived stress after this
traditional Buddhist meditation retreat.
Insomnia and sleep
Chronic insomnia is often associated with anxious hyperarousal and frustration over inability to sleep.
Mindfulness has been shown to reduce insomnia and improve sleep
quality, although self-reported measures show larger effects than
objective measures.
Future directions
A
large part of mindfulness research is dependent on technology. As new
technology continues to be developed, new imaging techniques will become
useful in this field. Real-time fMRI might give immediate feedback and
guide participants through the programs. It could also be used to more
easily train and evaluate mental statesFunctional magnetic resonance
imaging during meditation itself.
Effects of other types of meditation
Insight (Vipassana) meditation
Vipassana
or "insight" meditation is a form of mindfulness meditation believed to
have been taught by the Buddha himself. As such, it is one of the most
ancient forms of meditation. The practice aims to increase a sense of
awareness of the present moment. The practitioner becomes a quiet
observer of their thoughts, emotions, and sensations; allowing them to
come and go without passing judgement.
A plethora of evidence now exists to suggest that vipassana meditation
does indeed lead to increased mindfulness, but the benefits of the
practice do not stop there. It has also been found to reduce stress and
increase both self-kindness and overall well-being.
Electroencephalography studies on Vipassana meditators seemed to indicate significant increase in parieto-occipitalgamma rhythms in experienced meditators (35–45 Hz).
In another study conducted by NIMHANS
on Vipassana meditators, researchers found readings associated with
improved cognitive processing after a session of meditation, with
distinct and graded difference in the readings between novice meditators
and experienced meditators.
Khoury and colleagues (2017) conducted a meta-analysis including a
total of 21 studies and 2,912 participants. The study aimed to evaluate
the effects of traditional vipassana meditation retreats in various
populations including advanced meditators, novice meditators, and
incarcerated individuals. More specifically, it explored the
psychological outcomes including anxiety symptoms, depressive symptoms,
and stress following the retreats, evaluated the impacts of the retreats
on levels of mindfulness, and explored variables moderating the
effectiveness of traditional retreats. Results suggested that
traditional vipassana meditation retreats were moderately effective at
improving psychological outcomes, with novice meditators and members of
the general population experiencing particularly large reductions in
anxiety, depression, and stress when compared to both experienced
meditators and incarcerated individuals. Moreover, the results suggested
an increased capacity for emotional regulation, acceptance, compassion,
and mindfulness as well as higher quality of life scores following the
retreats across all populations. These results held steady even at
follow-up.
An essential component to the Vipassana mediation approach is the
focus on awareness, referring to bodily sensations and psychological
status. In a study conducted by Zeng et al. (2013), awareness was
described as the acknowledgement of consciousness which is monitoring
all aspects of the environment.
This definition differentiates the concept of awareness from
mindfulness. The emphasis on awareness, and the way it assists in
monitoring emotion, is unique to this meditative practice.
Kundalini yoga
Kundalini yoga
has proved to increase the prevention of cognitive decline and evaluate
the response of biomarkers to treatment, thereby shedding light on the
underlying mechanisms of the link between Kundalini Yoga and cognitive
impairment. For the study, 81 participants aged 55 and older who had
subjective memory complaints and met criteria for mild cognitive
impairment, indicated by a total score of 0.5 on the Clinical Dementia
Rating Scale. The results showed that at 12 weeks, both the yoga group
showed significant improvements in recall memory and visual memory and
showed a significant sustained improvement in memory up to the 24-week
follow-up, the yoga group showed significant improvement in verbal
fluency and sustained significant improvements in executive functioning
at week 24. In addition, the yoga cohort showed significant improvement
in depressive symptoms, apathy, and resilience from emotional stress.
This research was provided by Helen Lavretsky, M.D. and colleagues.
In another study, Kundalini Yoga did not show significant effectiveness
in treating obsessive-compulsive disorders compared with
Relaxation/Meditation.
Sahaja yoga and mental silence
Sahaja yoga meditation is regarded as a mental silence meditation, and has been shown to correlate with particular brain and brain wave
characteristics. One study has led to suggestions that Sahaja
meditation involves 'switching off' irrelevant brain networks for the
maintenance of focused internalized attention and inhibition of
inappropriate information. Sahaja meditators appear to benefit from lower depression and scored above control group for emotional well-being and mental health measures on SF-36 ratings.
A study comparing practitioners of Sahaja Yoga meditation with a
group of non-meditators doing a simple relaxation exercise, measured a
drop in skin temperature in the meditators compared to a rise in skin
temperature in the non-meditators as they relaxed. The researchers noted
that all other meditation studies that have observed skin temperature
have recorded increases and none have recorded a decrease in skin
temperature. This suggests that Sahaja Yoga meditation, being a mental
silence approach, may differ both experientially and physiologically
from simple relaxation.
Transcendental Meditation
In a 2006 review, Transcendental Meditation proved comparable with other kinds of relaxation therapies in reducing anxiety. In another 2006 review, study participants demonstrated a one Hertz reduction in electroencephalography alpha wave frequency relative to controls.
A 2012 meta-analysis published in Psychological Bulletin,
which reviewed 163 individual studies, found that Transcendental
Meditation performed no better overall than other meditation techniques
in improving psychological variables.
A 2013 statement from the American Heart Association said that Transcendental Meditation could be considered as a treatment for hypertension,
although other interventions such as exercise and device-guided
breathing were more effective and better supported by clinical evidence.
A 2014 review found moderate evidence for improvement in anxiety,
depression and pain with low evidence for improvement in stress and
mental health-related quality of life.
Transcendental Meditation may reduce blood pressure, according to a 2015 review that compared it to control groups.
A trend over time indicated that practicing Transcendental Meditation
may lower blood pressure. Such effects are comparable to other lifestyle interventions. Conflicting findings across reviews and a potential risk of bias indicated the necessity of further evidence.
Effects of loving, kindness, and compassion
Several
meta-analyses have examined the effects of mindful meditation on one’s
loving, kindness, and compassionate disposition and behaviors.
Significant increases in self-reported self-compassion. Compassion, and
well-being were reported alongside decreases in depression and anxiety. Another study indicated an increase in positive emotions.
There may be further benefits that are yet to be discovered, with only
preliminary data on mindfulness and mediation. Further studies and
explorations into the effects of mindful meditation on the self are
needed to draw further conclusions.
Research on unspecified or multiple types of meditation
The medial prefrontal and posterior cingulate
cortices have been found to be relatively deactivated during meditation
by experienced meditators using concentration, loving-kindness, and
choiceless awareness meditation.
In addition experienced meditators were found to have stronger coupling
between the posterior cingulate, dorsal anterior cingulate, and
dorsolateral prefrontal cortices both when meditating and when not
meditating. Over time meditation can actually increase the integrity of both gray and white matter.
The added amount of gray matter found in the brain stem after
meditation improves communication between the cortex and all other areas
within the brain. Meditation often stimulates a large network of cortical regions including the frontal and parietal regions, lateral occipital lobe, the insular cortex, thalamic nuclei, basal ganglia, and the cerebellum
region in the brain. These parts of the brain are connected with
attention and the default network of the brain which is associated to
day dreaming.
Strengthening of the caudate has been found in avid meditators and yogis.
In addition, both meditation and yoga have been found to have impacts on the brain, specifically the caudate. Strengthening of the caudate
has been shown in meditators as well as yogis. The increased
connectedness of the caudate has potential to be responsible for the
improved well-being that is associated with yoga and meditation.
Changes in the brain
Meditation is under preliminary research to assess possible changes in grey matter concentrations.
Published research suggests that meditation can facilitate
neuroplasticity and connectivity in brain regions specifically related
to emotion regulation and attention.
Attention and mind wandering
Non-directive
forms of meditation where the meditator lets their mind wander freely
can actually produce higher levels of activity in the default mode
network when compared to a resting state or having the brain in a
neutral place.
These Non directive forms of meditation allows the meditators to have
better control over thoughts during everyday activities or when focusing
on specific task due to a reduced frustration at the brains mind
wandering process.
When given a specific task, meditation can allow quicker response to
changing environmental stimuli. Meditation can allow the brain to
decrease attention to unwanted responses of irrelevant environmental
stimuli and a reduces the Stroop effect.
Those who meditate have regularly demonstrated more control on what
they focus their attention on while maintaining a mindful awareness on
what is around them. Experienced meditators have been shown to have an increased ability when it comes to conflict monitoring and find it easier to switch between competing stimuli.
Those who practice meditation experience an increase of attentional
resources in the brain and steady meditation practice can lead to the
reduction of the attentional blink due to a decreased mental exertion when identifying important stimuli.
Perception
Studies
have shown that meditation has both short-term and long-term effects on
various perceptual faculties. In 1984 a study showed that meditators
have a significantly lower detection threshold for light stimuli of
short duration.
In 2000 a study of the perception of visual illusions by zen masters,
novice meditators, and non-meditators showed statistically significant
effects found for the Poggendorff Illusion but not for the Müller-Lyer Illusion.
The zen masters experienced a statistically significant reduction in
initial illusion (measured as error in millimeters) and a lower
decrement in illusion for subsequent trials.
Tloczynski has described the theory of mechanism behind the changes in
perception that accompany mindfulness meditation thus: "A person who
meditates consequently perceives objects more as directly experienced
stimuli and less as concepts… With the removal or minimization of
cognitive stimuli and generally increasing awareness, meditation can
therefore influence both the quality (accuracy) and quantity (detection)
of perception."
Brown points to this as a possible explanation of the phenomenon: "[the
higher rate of detection of single light flashes] involves quieting
some of the higher mental processes which normally obstruct the
perception of subtle events."
In other words, the practice may temporarily or permanently alter some
of the top-down processing involved in filtering subtle events usually
deemed noise by the perceptual filters.
Memory
Meditation enhances memory capacity specifically in the working memory and increases executive functioning by helping participants better understand what is happening moment for moment.Those who meditate regularly have demonstrated the ability to better process and distinguish important information from the working memory and store it into long-term memory with more accuracy than those who do not practice meditation techniques.
Meditation may be able to expand the amount of information that can be
held within working memory and by so doing is able to improve IQ scores
and increase individual intelligence.
The encoding process for both audio and visual information has been
shown to be more accurate and detailed when meditation is used.
Though there are limited studies on meditation's effects on long-term
memory, because of meditations ability to increase attentional
awareness, episodic long-term memory
is believed to be more vivid and accurate for those who meditate
regularly. Meditation has also shown to decrease memory complaints from
those with Alzheimer's disease which also suggests the benefits
meditation could have on episodic long-term memory which is linked to
Alzheimer's.
Calming and relaxation
Electroencephalography activity slows as a result of meditation. Some types of meditation may lead to a calming effect by reducing sympathetic nervous system activity while increasing parasympathetic nervous system activity. Or, equivalently, that meditation produces a reduction in arousal and increase in relaxation.
Herbert Benson, founder of the Mind-Body Medical Institute, which is affiliated with Harvard University
and several Boston hospitals, reports that meditation induces a host of
biochemical and physical changes in the body collectively referred to
as the "relaxation response".
The relaxation response includes changes in metabolism, heart rate,
respiration, blood pressure and brain chemistry. Benson and his team
have also done clinical studies at Buddhist monasteries in the Himalayan Mountains. Benson wrote The Relaxation Response to document the benefits of meditation, which in 1975 were not yet widely known.
Aging
There is no good evidence to indicate that meditation affects the brain in aging.
Happiness and emotional well-being
Studies
have shown meditators to have higher happiness than control groups,
although this may be due to non-specific factors such as meditators
having better general self-care.
Positive relationships have been found between the volume of gray matter in the right precuneus area of the brain and both meditation and the subject's subjective happiness score. A recent study found that participants who engaged in a body-scan
meditation for about 20 minutes self-reported higher levels of happiness
and decrease in anxiety compared to participants who just rested during
the 20-minute time span. These results suggest that an increase in
awareness of one's body through meditation causes a state of
selflessness and a feeling of connectedness. This result then leads to
reports of positive emotions.
A technique known as mindfulness-based stress reduction
(MBSR) displays significant benefits for mental health and coping
behaviors. Participants who had no prior experience with MBSR reported a
significant increase in happiness after eight weeks of MBSR practice.
Focus on the present moment and increased awareness of one's thoughts
can help monitor and reduce judgment or negative thoughts, causing a
report of higher emotional well-being. The MBSR program and evidence for its effectiveness is described in Jon Kabat-Zinn's book Full Catastrophe Living.
Meditation has been shown to reduce pain perception. An intervention known as mindfulness-based pain management (MBPM) has been subject to a range of studies demonstrating its effectiveness.
Adverse effects and limits of meditation and mindfulness
Meditation and mindfulness have also been correlated with unpleasant
experiences, but the potential for adverse effects from meditation has
received limited attention in scientific articlesand the popular press.
Contemplative traditions
According to Farias et al. (2020) the most common adverse effects of meditation are anxiety and depression. Other adverse affects may include depersonalization or altered sense of self or the world,
distorted emotions or thoughts, and, in a few cases, visual and
auditory psychosis, and with pre-existing historical factors suicide.
Schlosser et al. (2019) reported that, of 1,232 regular
meditators with at least two months of meditation experience, about a
quarter reported having had particularly unpleasant meditation-related
experiences (such as anxiety, fear, distorted emotions or thoughts,
altered sense of self or the world), which they thought may have been
caused by their meditation practice. Meditators with high levels of
repetitive negative thinking and those who only engage in deconstructive
meditation were more likely to report unpleasant side effects. Adverse
effects were less frequently reported in women and religious meditators.
Meditation also has an addictive potential as it both offers
biochemical rewards and socially acceptable avenues for escapism (like
internet use, social media, substance abuse). Using spiritual ideas and practices "to sidestep or avoid facing
unresolved emotional issues, psychological wounds, and unfinished
developmental tasks" is known as Spiritual bypass, a term introduced in the mid 1980s by John Welwood, a Buddhist teacher and psychotherapist.
"Zen sickness", exhaustion caused by prolonged intense practice and self-neglect is described by Hakuin and Bankei.
Mindfulness
In
recent years both the soundness of the scientific foundations and the
desirability of the societal effects of mindfulness have been
questioned.
Britton et al. (2019), in a study on the effects of
mindfulness-based programs (MBPs), found negative side-effects in 37% of
the sample while lasting bad effects in 6–14% of the sample. Most of the side effects were related to signs of dysregulated arousal (i.e., hyperarousal and dissociation).
The majority of these adverse events occurred as a result of regular
practice at home or during class something that challenges the notion
that it is only intense practice that can give rise to negative
experiences; as it turns out intense all-day retreats or working with
difficulty practice accounts for only 6% of adverse effects. The
symptoms most readily recognized as negative were those of hyperarousal
(e.g., anxiety and insomnia). On the other hand, while dissociation symptoms (e.g., emotional blunting, derealization,
and self-disturbance) were both less frequent and less likely to be
appraised as negative, they were still associated with more than 5–10
times greater risk for lasting bad effects… This means that re-appraisal
of dissociative symptoms via non-judgmental acceptance is not
sufficient to prevent impairment in functioning and should not
constitute the only response. Instead, training in how to recognize
dissociative symptoms as potential indicators of the need for
intervention, which have recently been added to some mindfulness teacher
training programs may be important.
There is also mounting evidence that mindfulness can disturb various prosocial behaviors. By blunting emotions,
in particular the social emotions of guilt and shame, it may produce
deficits in the feelings of empathy and remorse thus creating calm but
callous practitioners. Hafenbrack et al. (2022), in a study on
mindfulness with 1400 participants, found that focused-breathing
meditation can dampen the relationship between transgressions and the
desire to engage in reparative prosocial behaviors. Poullin et al. (2021) found that mindfulness can increase the trait of selfishness.
The study, consisting of two interrelated parts and totaling 691
participants, found that a mindfulness induction, compared to a control
condition, led to decreased prosocial behavior. This effect was
moderated by self-construals such that people with relatively
independent self-construals became less prosocial while people with
relatively interdependent self-construals became more so. In the western
world where independent self-construals generally predominate
meditation may thus have potentially detrimental effects.
These new findings about mindfulness' socially problematic
effects imply that it can be contraindicated to use mindfulness as a
tool to handle acute personal conflicts or relational difficulties; in
the words of Andrew Hafenbrack, one of the authors of the study, “If we
'artificially' reduce our guilt by meditating it away, we may end up
with worse relationships, or even fewer relationships”.
In line with this, a meta-analysis by Kreplin et al. (2018) concluded
that meditation only has a limited effect in increasing prosocial
behaviours (e.g., empathy, compassion).
Mindfulness is not helpful if it used to avoid facing ongoing
problems or emerging crises in the meditator's life, in which case it
will function as just another form of experiential avoidance and
potentially exacerbate the crisis. In such situations, it may instead be
helpful to apply mindful attitudes while actively engaging with current problems. According to the NIH,
meditation and mindfulness should not be used as a replacement for
conventional health care or as a reason to postpone seeing a doctor.
Support
Organizations such as Cheetah House and Meditating in Safety
document research on problems arising in meditation, and offer help for
meditators in distress or those recovering from meditation-related
health problems. In some cases, adverse effects may be attributed to
"improper use of meditation"
or the aggravation of a preexisting condition; however, developing
research in this area suggests the need for deeper engagement with the
causes of severe distress, which previous "meditation teachers have
perhaps too quickly and rather insensitively dismissed as pre-existing
or unrelated psychopathology". Where meditation is prescribed or offered as a treatment,
principles of informed consent
require that treatment choice be based in part on the balance of
benefits to harms, and therefore can only be made if harms are
adequately measured and known.
Difficulties in the scientific study of meditation
Weaknesses in historic meditation and mindfulness research
A comparison of the effect of various meditation techniques on systolic blood pressure
Scientific research on meditation
practices does not appear to have a common theoretical perspective and
is characterized by poor methodological quality. Future research on
meditation practices must be more rigorous in the design and execution
of studies and in the analysis and reporting of results. (p. 6)
It noted that there is no theoretical explanation of health effects from meditation common to all meditation techniques.
A version of this report subsequently published in the Journal of Alternative and Complementary Medicine
in 2008 stated: "Most clinical trials on meditation practices are
generally characterized by poor methodological quality with significant
threats to validity in every major quality domain assessed." This was despite a statistically significant
increase in quality of all reviewed meditation research, in general,
over time between 1956 and 2005. Of the 400 clinical studies, 10% were
found to be good quality. A call was made for rigorous study of
meditation.
These authors also noted that this finding is not unique to the area of
meditation research and that the quality of reporting is a frequent
problem in other areas of complementary and alternative medicine (CAM)
research and related therapy research domains.
Of more than 3,000 scientific studies that were found in a comprehensive search of 17 relevant databases, only about 4% had randomised controlled trials (RCTs), which are designed to exclude the placebo effect.
In a 2013 meta-analysis, Awasthi argued that meditation is
defined poorly and despite the research studies showing clinical
efficacy, exact mechanisms of action remain unclear.
A 2017 commentary was similarly mixed,
with concerns including the particular characteristics of individuals
who tend to participate in mindfulness and meditation research.
Position statements
A 2013 statement from the American Heart Association
evaluated the evidence for the effectiveness of Transcendental
Meditation as a treatment for hypertension as "unknown/unclear/uncertain
or not well-established", and stated: "Because of many negative studies
or mixed results and a paucity of available trials... other meditation
techniques are not recommended in clinical practice to lower BP at this
time."
According to the American Heart Association, while there are promising
results about the impact of meditation in reducing blood pressure and
managing insomnia, depression and anxiety, it is not a replacement for
healthy lifestyle changes and is not a substitute for effective
medication.
Methodological obstacles
The term meditation
encompasses a wide range of practices and interventions rooted in
different traditions, but research literature has sometimes failed to
adequately specify the nature of the particular meditation practice(s)
being studied. Different forms of meditation practice may yield different results depending on the factors being studied.
The presence of a number of intertwined factors including the
effects of meditation, the theoretical orientation of how meditation
practices are taught, the cultural background of meditators, and generic
group effects complicates the task of isolating the effects of
meditation:
Numerous studies have demonstrated
the beneficial effects of a variety of meditation practices. It has been
unclear to what extent these practices share neural correlates.
Interestingly, a recent study compared electroencephalogram activity
during a focused-attention and open monitoring meditation practice from
practitioners of two Buddhist
traditions. The researchers found that the differences between the two
meditation traditions were more pronounced than the differences between
the two types of meditation. These data are consistent with our findings
that theoretical orientation of how a practice is taught strongly
influences neural activity during these practices. However, the study
used long-term practitioners from different cultures, which may have
confounded the results.
Quantum mysticism, sometimes referred pejoratively to as quantum quackery or quantum woo, is a set of metaphysical beliefs and associated practices that seek to relate consciousness, intelligence, spirituality, or mystical worldviews to the ideas of quantum mechanics and its interpretations. Quantum mysticism is considered pseudoscience and quackery by quantum mechanics experts.
Before the 1970s the term was usually used in reference to the von Neumann–Wigner interpretation, but was later more closely associated with the purportedly pseudoscientific views espoused by New Age thinkers such as Fritjof Capra and other members of the Fundamental Fysiks Group, who were influential in popularizing the modern form of quantum mysticism.
Olav Hammer said that "Schrödinger’s studies of Hindu mysticism never compelled him to pursue the same course as quantum metaphysicists such as David Bohm or Fritjof Capra."
Schrödinger biographer Walter J. Moore said that Schrödinger's two
interests of quantum physics and Hindu mysticism were "strangely
dissociated".
In his 1961 paper "Remarks on the mind–body question", Eugene Wigner suggested that a conscious observer played a fundamental role in quantum mechanics, a concept which is part of the von Neumann–Wigner interpretation. While his paper served as inspiration for later mystical works by others, Wigner's ideas were primarily philosophical and were not considered overtly pseudoscientific like the mysticism that followed. By the late 1970s, Wigner had shifted his position and rejected the role of consciousness in quantum mechanics.
Harvard historian Juan Miguel Marin suggests that "consciousness [was]
introduced hypothetically at the birth of quantum physics, [and] the
term 'mystical' was also used by its founders, to argue in favor of and
against such an introduction."
Mysticism was argued against by Albert Einstein.
Einstein's theories have often been falsely believed to support
mystical interpretations of quantum theory. Einstein said, with regard
to quantum mysticism, "No physicist believes that. Otherwise he wouldn't
be a physicist." He debates several arguments about the approval of mysticism, even suggesting Bohr and Pauli to be in support of and to hold a positive belief in mysticism which he believes to be false.
Niels Bohr denied quantum mysticism and had rejected the
hypothesis that quantum theory requires a conscious observer as early as
1927,
despite having been "sympathetic towards the hypothesis that
understanding consciousness might require an extension of quantum theory
to accommodate laws other than those of physics".
In contrast to the mysticism of the early 20th century, today quantum mysticism typically refers to New Age beliefs that combine ancient mysticism with the language of quantum mechanics. Called a pseudoscience
and a "hijacking" of quantum physics, it draws upon "coincidental
similarities of language rather than genuine connections" to quantum
mechanics. Physicist Murray Gell-Mann coined the phrase "quantum flapdoodle" to refer to the misuse and misapplication of quantum physics to other topics.
An example of such use is New Age guru Deepak Chopra's "quantum theory" that aging is caused by the mind, expounded in his books Quantum Healing (1989) and Ageless Body, Timeless Mind (1993). In 1998, Chopra was awarded the parody Ig Nobel Prize
in the physics category for "his unique interpretation of quantum
physics as it applies to life, liberty, and the pursuit of economic
happiness". In 2012, Stuart Hameroff
and Chopra proposed that the "quantum soul" could exist "apart from the
body" and "in space-time geometry, outside the brain, distributed
nonlocally".
