Anterior cingulate cortex
Encyclopedia
The anterior cingulate cortex (ACC) is the frontal part of the cingulate cortex
, that resembles a "collar" form around the corpus callosum
, the fibrous bundle that relays neural signals
between the right and left cerebral hemisphere
s of the brain
. It includes both the ventral
and dorsal
areas
of the cingulate cortex, and appears to play a role in a wide variety of autonomic
functions, such as regulating blood pressure
and heart rate
, as well as rational
cognitive functions, such as reward anticipation, decision-making, empathy
and emotion
.
), and emotional (ventral) components. The dorsal part of the ACC is connected with the prefrontal cortex
and parietal cortex as well as the motor system and the frontal eye fields
making it a central station for processing top-down and bottom-up stimuli and assigning appropriate control to other areas in the brain. By contrast, the ventral part of the ACC is connected with amygdala
, nucleus accumbens
, hypothalamus
, and anterior insula
, and is involved in assessing the salience of emotion and motivational information. The ACC seems to be especially involved when effort is needed to carry out a task such as in early learning and problem-solving.
and consists of an arrow pointing to the left or right, which is flanked by two distractor arrows creating either compatible (<<<<<) or incompatible (<<<>>) trials. Another very common conflict-inducing stimulus is the Stroop task (Pardo et al., 1990), which involves naming the color ink of words that are either congruent (RED written in red) or incongruent (RED written in blue). Conflict occurs because people’s reading abilities interfere with their attempt to correctly name the word’s ink color. A variation of this task is the Counting-Stroop, during which people count either neutral stimuli (‘dog’ presented four times) or interfering stimuli (‘three’ presented four times) by pressing a button. Another version of the Stroop task named the Emotional Counting Stroop is identical to the Counting Stroop test, except that it also uses segmented or repeated emotional words such as "murder" during the interference part of the task.
, motivation
, and modulation of emotional responses to the ACC.
A similar theory poses that the ACC’s primary function is the monitoring of conflict. In Eriksen flanker task
, incompatible trials produce the most conflict and, the most activation by the ACC. Upon detection of a conflict, the ACC then provides cues to other areas in the brain to cope with the conflicting control systems.
Evidence from electrical studies
Evidence for ACC as having an error detection function comes from observations of error-related negativity
(ERN) uniquely generated within the ACC upon error occurrences. A distinction has been made between an ERP
following incorrect responses (response ERN) and a signal after subjects receive feedback after erroneous responses (feedback ERN).
No-one has clearly demonstrated that the ERN comes from the ACC. Related to this it is striking that patients with lateral PFC damage showed reduced ERNs.
Reinforcement learning ERN theory poses that there is a mismatch between actual response execution and appropriate response execution, which results in an ERN discharge. Furthermore, this theory predicts that, when the ACC receives conflicting input from control areas in the brain, it determines and allocates which area should be given control over the motor system. Varying levels of dopamine are believed to influence the optimization of this filter system by providing expectations about the outcomes of an event. The ERN then, serves as a beacon to highlight the violation of an expectation. Research on the occurrence of the feedback ERN shows evidence that this potential has larger amplitudes when violations of expectancy are large. In other words, if an event is not likely to happen the feedback ERN will be larger if no error is detected. Other studies have examined if the ERN is elicited by varying the cost of an error and the evaluation of a response.
In these trials, feedback is given about whether the participant has gained or lost money after a response. Amplitudes of ERN responses with small gains and small losses were similar. No ERN was elicited for any losses as opposed to an ERN for no wins, even though both outcomes are the same. The finding in this paradigm suggests that monitoring for wins and losses is based on the relative expected gains and losses. If you get a different outcome than expected, the ERN will be larger than for expected outcomes. ERN studies have also localized specific functions of the ACC.
The rostral ACC seems to be active after an error commission, indicating an error response function, whereas the dorsal ACC is active after both an error and feedback, suggesting a more evaluative function (for fMRI evidence, see also ). This evaluation is emotional in nature and highlights the amount of distress associated with a certain error. Summarizing the evidence found by ERN studies it appears to be the case that ACC receives information about a stimulus, selects an appropriate response, monitors the action, and adapts behavior if there is a violation of expectancy.
Evidence against error detection and conflict monitoring theory
Studies examining task performance related to error and conflict processes in patients with ACC damage, cast doubt on the necessity of this region for these functions. The error detection and conflict monitoring theories cannot explain some evidence obtained by electrical studies that demonstrate the effects of giving feedback after responses because the theory describes the ACC as strictly monitoring conflict, not as having evaluative properties.
It has been stated that "The cognitive consequences of anterior cingulate lesions remain rather equivocal, with a number of case reports of intact general neuropsychological and executive function in the presence of large anterior dorsal cingulate lesions.See Review by Critchely related to this For an alternative view of anterior cingulate, see Rushworth's review (2007).
The dorsal and rostral areas of the ACC both seem to be affected by rewards and losses associated with errors. During one study, participants received monetary rewards and losses for correct and incorrect responses respectively.
Largest activation in the dACC was shown during loss trials. This stimulus did not elicit any errors, and, thus, error detection and monitoring theories cannot fully explain why this ACC activation would occur. The dorsal part of the ACC seems to play a key role in reward-based decision-making and learning. The rostral part of the ACC, on the other hand, is believed to be more involved with affective responses to errors. In an interesting expansion of the previously described experiment, the effects of rewards and costs on ACC’s activation during error commission was examined. Participants performed a version of the Eriksen flanker task
using a set of letters assigned to each response button instead of arrows.
Targets were flanked by either a congruent or an incongruent set of letters. Using an image of a thumb (up, down, or neutral), participants received feedback on how much money they gained or lost. The researchers found greater rostral ACC activation when participants lost money during the trials. The participants reported being frustrated when making mistakes. Because the ACC is intricately involved with error detection and affective responses, it may very well be that this area forms the bases of self-confidence. Taken together, these findings indicate that both the dorsal and rostral areas are involved in evaluating the extent of the error and optimizing subsequent responses. A study confirming this notion explored the functions of both the dorsal and rostral areas of the ACC involved using a saccade task.
Participants were shown a cue that indicated whether they had to make either a pro-saccade or an anti-saccade. An anti-saccade requires suppression of a distracting cue because the target appears in the opposite location causing the conflict. Results showed differing activation for the rostral and dorsal ACC areas. Early correct anti-saccade performance was associated with rostral activation. The dorsal area, on the other hand, was activated when errors were committed, but also for correct responses.
Whenever the dorsal area was active, fewer errors were committed providing more evidence that the ACC is involved with effortful
performance. The second finding showed that, during error trials, the ACC activated later than for correct responses, clearly indicating a kind of evaluative function.
The idea of awareness being associated with the ACC has some evidence with it, in that it seems to be the case that, when subjects' responses are not congruent with actual responses, a larger ERN is produced.
One study found an ERN even when subjects were not aware of their error. Awareness may not be necessary to elicit an ERN, but it could influence the effect of the amplitude of the feedback ERN. Relating back to the reward-based learning theory, awareness could modulate expectancy violations. Increased awareness could result in decreased violations of expectancies and decreased awareness could achieve the opposite effect. Further research is needed to completely understand the effects of awareness on ACC activation.
demonstrated a correlation between larger development of the ACC and left political orientation versus larger development of the amygdala
in right political orientation.
in neurosurgical studies has been shown to improve depression in a portion of test subjects.
Studying the effects of damage to the ACC provides insights into the type of functions it serves in the intact brain. Behavior that is associated with lesions in the ACC includes: inability to detect errors, severe difficulty with resolving stimulus conflict in a Stroop task, emotional instability, inattention, and akinetic mutism
. There is evidence that damage to ACC is present in patients with schizophrenia
, where studies have shown patients have difficulty in dealing with conflicting spatial locations in a Stroop-like task and having abnormal ERNs. Participants with ADHD were found to have reduced activation in the dorsal area of the ACC when performing the Stroop task. Together these findings corroborate results from imaging and electrical studies about the variety of functions attributed to the ACC.
There is evidence that this area may have a role in obsessive–compulsive disorder due to the fact that what appears to be an unnaturally low level of glutamate activity in this region has been observed in patients with the disorder, in strange contrast to many other brain regions that are thought to have excessive glutamate activity in OCD. Recent SDM meta-analyses
of voxel-based morphometry studies comparing people with OCD and healthy controls has 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 cortex. 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.
Helen S. Mayberg
and two collaborators described how they cured 4 of 6 depressed people — individuals virtually catatonic with depression despite years of talk therapy, drugs, even shock therapy — with pacemakerlike electrodes in area 25. A decade earlier, Mayberg
had identified area 25 as a key conduit of neural traffic between the "thinking" frontal cortex and the phylogenetically older central limbic region that gives rise to emotion. She subsequently found that area 25 appeared overactive in these depressed people — "like a gate left open," as she puts it — allowing negative emotions to overwhelm thinking and mood. Inserting the electrodes closed this gate and rapidly alleviated the depression of two-thirds of the trial's patients.
It has also been suggested to have possible links with Social Anxiety, along with the amygdala part of the brain, but is still in the early stages of research.
A 2008 study of brain MRIs taken on adults that had previously participated in the Cincinnati Lead Study demonstrated that people that had suffered higher levels of lead poisoning
as children had decreased brain size as adults. This effect was most pronounced in the ACC (Cecil et al., 2008) and is thought to relate to the cognitive and behavioral deficits of affected individuals.
Cingulate cortex
The cingulate cortex is a part of the brain situated in the medial aspect of the cortex. It includes the cortex of the cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus...
, that resembles a "collar" form around the corpus callosum
Corpus callosum
The corpus callosum , also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication...
, the fibrous bundle that relays neural signals
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
between the right and left cerebral hemisphere
Cerebral hemisphere
A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...
s of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. It includes both the ventral
Brodmann area 24
-Human:In the human this area is known as ventral anterior cingulate area 24, and it refers to a subdivision of the cytoarchitecturally defined cingulate cortex region of cerebral cortex . It occupies most of the anterior cingulate gyrus in an arc around the genu of corpus callosum. Its outer...
and dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
areas
Brodmann area 32
The Brodmann area 32, also known in the human brain as the dorsal anterior cingulate area 32, refers to a subdivision of the cytoarchitecturally defined cingulate region of cerebral cortex. In the human it forms an outer arc around the anterior cingulate gyrus...
of the cingulate cortex, and appears to play a role in a wide variety of autonomic
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
functions, such as regulating blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
and heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
, as well as rational
Rationality
In philosophy, rationality is the exercise of reason. It is the manner in which people derive conclusions when considering things deliberately. It also refers to the conformity of one's beliefs with one's reasons for belief, or with one's actions with one's reasons for action...
cognitive functions, such as reward anticipation, decision-making, empathy
Empathy
Empathy is the capacity to recognize and, to some extent, share feelings that are being experienced by another sapient or semi-sapient being. Someone may need to have a certain amount of empathy before they are able to feel compassion. The English word was coined in 1909 by E.B...
and emotion
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
.
Anatomy
The anterior cingulate cortex can be divided anatomically based on cognitive (dorsalDorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
), and emotional (ventral) components. The dorsal part of the ACC is connected with the prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
and parietal cortex as well as the motor system and the frontal eye fields
Frontal eye fields
The frontal eye fields is a region located in the premotor cortex, which is part of the frontal cortex of the primate brain.-Function:...
making it a central station for processing top-down and bottom-up stimuli and assigning appropriate control to other areas in the brain. By contrast, the ventral part of the ACC is connected with amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
, nucleus accumbens
Nucleus accumbens
The nucleus accumbens , also known as the accumbens nucleus or as the nucleus accumbens septi , is a collection of neurons and forms the main part of the ventral striatum...
, hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
, and anterior insula
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
, and is involved in assessing the salience of emotion and motivational information. The ACC seems to be especially involved when effort is needed to carry out a task such as in early learning and problem-solving.
Tasks
A typical task that activates the ACC involves eliciting some form of conflict within the participant that can potentially result in an error. One such task is called the Eriksen flanker taskEriksen flanker task
This term refers to a group of response inhibition tests used in cognitive psychology to assess the ability to supress responses that are inappropriate in a particular context. In the flanker paradigm, a directional response is made to a central target stimulus...
and consists of an arrow pointing to the left or right, which is flanked by two distractor arrows creating either compatible (<<<<<) or incompatible (<<<>>) trials. Another very common conflict-inducing stimulus is the Stroop task (Pardo et al., 1990), which involves naming the color ink of words that are either congruent (RED written in red) or incongruent (RED written in blue). Conflict occurs because people’s reading abilities interfere with their attempt to correctly name the word’s ink color. A variation of this task is the Counting-Stroop, during which people count either neutral stimuli (‘dog’ presented four times) or interfering stimuli (‘three’ presented four times) by pressing a button. Another version of the Stroop task named the Emotional Counting Stroop is identical to the Counting Stroop test, except that it also uses segmented or repeated emotional words such as "murder" during the interference part of the task.
Functions
Many studies attribute functions such as error detection, anticipation of tasks, attentionAttention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
, motivation
Motivation
Motivation is the driving force by which humans achieve their goals. Motivation is said to be intrinsic or extrinsic. The term is generally used for humans but it can also be used to describe the causes for animal behavior as well. This article refers to human motivation...
, and modulation of emotional responses to the ACC.
Error detection and conflict monitoring
The most basic form of ACC theory states that the ACC is involved with error detection. Evidence has been derived from studies involving a Stroop task. However, ACC is also active during correct response and this has been shown using a letter task, whereby participants had to respond to the letter X after an A was presented and ignore all other letter combinations with some letters being more competitive than others. They found that for more competitive stimuli ACC activation was greater.A similar theory poses that the ACC’s primary function is the monitoring of conflict. In Eriksen flanker task
Eriksen flanker task
This term refers to a group of response inhibition tests used in cognitive psychology to assess the ability to supress responses that are inappropriate in a particular context. In the flanker paradigm, a directional response is made to a central target stimulus...
, incompatible trials produce the most conflict and, the most activation by the ACC. Upon detection of a conflict, the ACC then provides cues to other areas in the brain to cope with the conflicting control systems.
Evidence from electrical studies
Evidence for ACC as having an error detection function comes from observations of error-related negativity
Error-related negativity
Error-related negativity , , is a component of an event-related potential . ERPs are electrical activity in the brain as measured through electroencephalography and time-locked to an external event...
(ERN) uniquely generated within the ACC upon error occurrences. A distinction has been made between an ERP
Event-related potential
An event-related potential is any measured brain response that is directly the result of a thought or perception. More formally, it is any stereotyped electrophysiological response to an internal or external stimulus....
following incorrect responses (response ERN) and a signal after subjects receive feedback after erroneous responses (feedback ERN).
No-one has clearly demonstrated that the ERN comes from the ACC. Related to this it is striking that patients with lateral PFC damage showed reduced ERNs.
Reinforcement learning ERN theory poses that there is a mismatch between actual response execution and appropriate response execution, which results in an ERN discharge. Furthermore, this theory predicts that, when the ACC receives conflicting input from control areas in the brain, it determines and allocates which area should be given control over the motor system. Varying levels of dopamine are believed to influence the optimization of this filter system by providing expectations about the outcomes of an event. The ERN then, serves as a beacon to highlight the violation of an expectation. Research on the occurrence of the feedback ERN shows evidence that this potential has larger amplitudes when violations of expectancy are large. In other words, if an event is not likely to happen the feedback ERN will be larger if no error is detected. Other studies have examined if the ERN is elicited by varying the cost of an error and the evaluation of a response.
In these trials, feedback is given about whether the participant has gained or lost money after a response. Amplitudes of ERN responses with small gains and small losses were similar. No ERN was elicited for any losses as opposed to an ERN for no wins, even though both outcomes are the same. The finding in this paradigm suggests that monitoring for wins and losses is based on the relative expected gains and losses. If you get a different outcome than expected, the ERN will be larger than for expected outcomes. ERN studies have also localized specific functions of the ACC.
The rostral ACC seems to be active after an error commission, indicating an error response function, whereas the dorsal ACC is active after both an error and feedback, suggesting a more evaluative function (for fMRI evidence, see also ). This evaluation is emotional in nature and highlights the amount of distress associated with a certain error. Summarizing the evidence found by ERN studies it appears to be the case that ACC receives information about a stimulus, selects an appropriate response, monitors the action, and adapts behavior if there is a violation of expectancy.
Evidence against error detection and conflict monitoring theory
Studies examining task performance related to error and conflict processes in patients with ACC damage, cast doubt on the necessity of this region for these functions. The error detection and conflict monitoring theories cannot explain some evidence obtained by electrical studies that demonstrate the effects of giving feedback after responses because the theory describes the ACC as strictly monitoring conflict, not as having evaluative properties.
It has been stated that "The cognitive consequences of anterior cingulate lesions remain rather equivocal, with a number of case reports of intact general neuropsychological and executive function in the presence of large anterior dorsal cingulate lesions.See Review by Critchely related to this For an alternative view of anterior cingulate, see Rushworth's review (2007).
Reward-based learning theory
A more comprehensive and recent theory describes the ACC as a more active component and poses that it detects and monitors errors, evaluates the degree of the error, and then suggests an appropriate form of action to be implemented by the motor system. Earlier evidence from electrical studies indicate the ACC has an evaluative component, which is indeed confirmed by fMRI studies.The dorsal and rostral areas of the ACC both seem to be affected by rewards and losses associated with errors. During one study, participants received monetary rewards and losses for correct and incorrect responses respectively.
Largest activation in the dACC was shown during loss trials. This stimulus did not elicit any errors, and, thus, error detection and monitoring theories cannot fully explain why this ACC activation would occur. The dorsal part of the ACC seems to play a key role in reward-based decision-making and learning. The rostral part of the ACC, on the other hand, is believed to be more involved with affective responses to errors. In an interesting expansion of the previously described experiment, the effects of rewards and costs on ACC’s activation during error commission was examined. Participants performed a version of the Eriksen flanker task
Eriksen flanker task
This term refers to a group of response inhibition tests used in cognitive psychology to assess the ability to supress responses that are inappropriate in a particular context. In the flanker paradigm, a directional response is made to a central target stimulus...
using a set of letters assigned to each response button instead of arrows.
Targets were flanked by either a congruent or an incongruent set of letters. Using an image of a thumb (up, down, or neutral), participants received feedback on how much money they gained or lost. The researchers found greater rostral ACC activation when participants lost money during the trials. The participants reported being frustrated when making mistakes. Because the ACC is intricately involved with error detection and affective responses, it may very well be that this area forms the bases of self-confidence. Taken together, these findings indicate that both the dorsal and rostral areas are involved in evaluating the extent of the error and optimizing subsequent responses. A study confirming this notion explored the functions of both the dorsal and rostral areas of the ACC involved using a saccade task.
Participants were shown a cue that indicated whether they had to make either a pro-saccade or an anti-saccade. An anti-saccade requires suppression of a distracting cue because the target appears in the opposite location causing the conflict. Results showed differing activation for the rostral and dorsal ACC areas. Early correct anti-saccade performance was associated with rostral activation. The dorsal area, on the other hand, was activated when errors were committed, but also for correct responses.
Whenever the dorsal area was active, fewer errors were committed providing more evidence that the ACC is involved with effortful
Effortfulness
In psychology effortfulness is the subjective experience of exertion in connection with an activity, but especially the mental aspects of an activity. In many applications, effortfulness is simply reported by a patient, client, or experimental subject. There has been some work establishing an...
performance. The second finding showed that, during error trials, the ACC activated later than for correct responses, clearly indicating a kind of evaluative function.
Role in consciousness
The ACC area in the brain is associated with many functions which are correlated with conscious experience. Greater ACC activation levels were present in more emotionally-aware female participants when shown short ‘emotional’ video clips. Better emotional awareness is associated with improved recognition of emotional cues or targets, which is reflected by ACC activation.The idea of awareness being associated with the ACC has some evidence with it, in that it seems to be the case that, when subjects' responses are not congruent with actual responses, a larger ERN is produced.
One study found an ERN even when subjects were not aware of their error. Awareness may not be necessary to elicit an ERN, but it could influence the effect of the amplitude of the feedback ERN. Relating back to the reward-based learning theory, awareness could modulate expectancy violations. Increased awareness could result in decreased violations of expectancies and decreased awareness could achieve the opposite effect. Further research is needed to completely understand the effects of awareness on ACC activation.
Role in registering pain
The ACC registers physical pain as shown in functional MRI studies which showed an increase in signal intensity, typically in the posterior part of area 24 of the ACC, that was correlated with pain intensity. When this pain-related activation was accompanied by attention-demanding cognitive tasks (verbal fluency), the attention-demanding tasks increased signal intensity in a region of the ACC anterior and/or superior to the pain-related activation region.Role in political orientation
A widely publicized study by the University College LondonUniversity College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of London...
demonstrated a correlation between larger development of the ACC and left political orientation versus larger development of the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
in right political orientation.
Pathology
Stimulation of the anterior cingulate (also known as Area 25) with low dosages of electric currentElectric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
in neurosurgical studies has been shown to improve depression in a portion of test subjects.
Studying the effects of damage to the ACC provides insights into the type of functions it serves in the intact brain. Behavior that is associated with lesions in the ACC includes: inability to detect errors, severe difficulty with resolving stimulus conflict in a Stroop task, emotional instability, inattention, and akinetic mutism
Akinetic mutism
Akinetic mutism is a medical term describing patients who tend neither to speak nor move . It is the result of severe frontal lobe injury in which the pattern of inhibitory control is one of increasing passivity and gradually decreasing speech and motion.An example of a cause of this disorder...
. There is evidence that damage to ACC is present in patients with schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, where studies have shown patients have difficulty in dealing with conflicting spatial locations in a Stroop-like task and having abnormal ERNs. Participants with ADHD were found to have reduced activation in the dorsal area of the ACC when performing the Stroop task. Together these findings corroborate results from imaging and electrical studies about the variety of functions attributed to the ACC.
There is evidence that this area may have a role in obsessive–compulsive disorder due to the fact that what appears to be an unnaturally low level of glutamate activity in this region has been observed in patients with the disorder, in strange contrast to many other brain regions that are thought to have excessive glutamate activity in OCD. Recent SDM meta-analyses
Signed differential mapping
Signed differential mapping or SDM is a statistical technique for meta-analyzing studies on differences in brain activity or structure which used neuroimaging techniques such as fMRI, VBM, DTI or PET...
of voxel-based morphometry studies comparing people with OCD and healthy controls has found people with OCD to have increased grey matter
Grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil , glial cells and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts...
volumes in bilateral lenticular nuclei, extending to the caudate nuclei
Caudate nucleus
The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system.-Anatomy:...
, while decreased grey matter volumes in bilateral dorsal medial frontal
Medial frontal gyrus
The superior frontal gyrus is situated above the superior frontal sulcus and is continued on to the medial surface of the hemisphere, the medial frontal gyrus...
/anterior cingulate cortex. These findings contrast with those in people with other anxiety disorders, who evince decreased (rather than increased) grey matter
Grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil , glial cells and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts...
volumes in bilateral lenticular / caudate nuclei
Caudate nucleus
The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system.-Anatomy:...
, while also decreased grey matter volumes in bilateral dorsal medial frontal
Medial frontal gyrus
The superior frontal gyrus is situated above the superior frontal sulcus and is continued on to the medial surface of the hemisphere, the medial frontal gyrus...
/ anterior cingulate gyri.
Helen S. Mayberg
Helen S. Mayberg
Helen S. Mayberg, M.D. was born in 1956 in California. She is an American neurologist.Dr. Mayberg is known in particular for her work delineating abnormal brain function in patients with major depression using functional neuroimaging...
and two collaborators described how they cured 4 of 6 depressed people — individuals virtually catatonic with depression despite years of talk therapy, drugs, even shock therapy — with pacemakerlike electrodes in area 25. A decade earlier, Mayberg
Helen S. Mayberg
Helen S. Mayberg, M.D. was born in 1956 in California. She is an American neurologist.Dr. Mayberg is known in particular for her work delineating abnormal brain function in patients with major depression using functional neuroimaging...
had identified area 25 as a key conduit of neural traffic between the "thinking" frontal cortex and the phylogenetically older central limbic region that gives rise to emotion. She subsequently found that area 25 appeared overactive in these depressed people — "like a gate left open," as she puts it — allowing negative emotions to overwhelm thinking and mood. Inserting the electrodes closed this gate and rapidly alleviated the depression of two-thirds of the trial's patients.
It has also been suggested to have possible links with Social Anxiety, along with the amygdala part of the brain, but is still in the early stages of research.
A 2008 study of brain MRIs taken on adults that had previously participated in the Cincinnati Lead Study demonstrated that people that had suffered higher levels of lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
as children had decreased brain size as adults. This effect was most pronounced in the ACC (Cecil et al., 2008) and is thought to relate to the cognitive and behavioral deficits of affected individuals.