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Function of the Anterior Cingulate Cortex

The anterior cingulate cortex (ACC) is involved in high level functions which include,emotion and social regulation, decision making, emotion-based learning, error detecting, performance monitoring, pain perception, and empathy.

Dysfunction of the Anterior Cingulate Cortex

The ACC connects both the emotional limbic system and the cognitive prefrontal cortex; thus, it has an important role as a regulator in these areas .  It can control and manage uncomfortable emotions; research has looked at the ACC for understanding various disorders, such as understanding psychopaths’ negative emotions and behaviours. Dysfunction in this area can cause decision making, attention, reward, impulse control and emotion regulation problems.

Neuropsychological effects

Rostral-ACC (RACC)

Patients with rostral-ACC dysfunction often have issues with emotion regulation and error processing, this is due to the dysfunction of the interconnected regions. Smaller or larger volume of the rostral-ACC can affect its regular function. The lack of or the excess of the neurotransmitter serotonin in this area can also cause issues, too much can cause hyperactivity of the area and a lack of can cause hypo-activity. The amygdala response can be exaggerated by lack of regulation, fear response can increase, perception of anger can also be altered. Those with depression also show an enhanced amygdala response to unattended fear-related stimuli. Dysfunction of the rostral-ACC can also cause lack of integration between the individual's attentional and affective or motivational state, which can result in disturbed or reduced goal-directed behaviour and manifest in the form of negative symptoms (e.g., apathy, avolition, hypo-arousal and anhedonia).

Dorsal-ACC (DACC)

The dorsal-ACC is involved in reward-based decision making, therefore important when thinking about reward, emotion, motivation, cognition and motor control. It is also involved in top-down control on frontal eye field (FEF). Regular function of the dACC, both eyes would be move quick and simultaneous (saccade). Decreased dACC activation correlates with a higher saccade error rate. Furthermore, the dACC mediates or modulates fear expression in humans, therefore is important area to study in relation to anxiety related disorders.

Ventral- ACC (VACC)

Individuals who have lower ventral ACC and higher left lateral prefrontal cortex activation experience greater social pain. Research has found that neurotypical individuals have less activity in the VACC when they are not emotionally supported, those that are not emotionally supported have more activation in this area and report less social pain. The VACC also plays a role in emotion, prior to having cognitive behavioral therapy, activation in the VACC was low. Once the therapy was completed, there was an increase in activation, it is believed that the VACC is negatively correlated with depressive symptoms.

Disorders

Schizophrenia

Dysfunction of the the ACC can explain the symptoms of those with Schizophrenia. The lower volume of the ACC causes hypo-activity within it, therefore it does not regulate properly causing decreased attentional responsiveness. An amino acid decrease of N-acetylaspartate (NAA) has also been found in the ACC which may reflect the dysfunction related to schizophrenia. In addition, there is a decreased blood oxygen in more dorsal regions of the ACC than in healthy participants. Bipolar disorder (BD) is a severe neuro-psychiatric illness that mainly affects mood regulation. Complex alterations of VACC reduces and/or alters the activation to other frontal brain regions correlating with the BD symptoms. Without the regular function of the VACC it explains the erratic mood swings of those with BD, this similarly has been found in those with schizophrenia.

Obsessive Compulsive Disorder

It is also commonly found, increased expression of the ACC is involved in Obsessive Compulsive Disorder (OCD). The opposite to schizophrenia it increases their attentional responsiveness. In a comparison study it was found that both healthy and OCD participants had activation in the rostral-ACC, although more error related responses were due to hyperactivity abnormality within the RACC. More research has found that Glutamine/glutamate ratio is involved in the rACC activation. Looking at healthy and OCD participants, the OCD participants displayed significantly reduced deactivation of the DACC when completing the stroop task, therefore making more errors.

Attention Deficit Hyperactivity Disorder (ADHD)

Research has found those with attention deficit hyperactivity disorder (ADHD) have significantly lower grey matter volume of the ACC than that of a neurortypical person. This gives a biological deficit to the disorder and also an explanation for their smaller attention span and lower executive control. Those with ADHD have significant cortical thinning in the right rostral ACC, they also performance poorly on the stroop task, compared to healthy participants. This is suggests a reason for their lack of behavioral error detection, inhibitory control and their implusivity.

Autism spectrum disorder (ASD)

Research has found that within an ASD group in comparison with a neurotypical group, that increased frontal eye field (FEF) activation and dorsal ACC and FEF functional connectivity were associated with more severe restricted repetitive behaviours. Lack of expression in the ACC has a role in the regulation of social behavior, which indicates the dysfunction in those with Autism spectrum disorder. The study found that increased expression of SHANK 3 in the ACC in those who initially had lower activation improved social regulation. From a meta analysis, it was found that less activation in the ACC was linked to the basic disturbance in social orienting in autism. The ACC is involved in self-awareness and integrates this self-related information to other people (Theory of mind). Joint attention is affected due to this dysfunction, therefore during development it can increase the severity of the symptoms for people with autism. Thus, impairment in the development of this system can result in social and cognitive deficits.

Parkinson's disease (PD)

Parkinson's disease patients with apathy and depression, have early disruptions to the ACC, structural changes cause nondopaminergic projections which is thought to be involved in the neuro-psychiatric symptoms in PD. Also, a low ratio of N-acetyle aspartate/creatine (NAA/Cr) in the ACC plays a role in executive dysfunction and visual hallucinations in PD. There is also a reduction of FDOPA uptake in the anterior cingulate cortex, this alters the dopaminergic function of those with PD, possibly an explanation of personality changes and cognititve decline.

Psychopathy

A lot of research has looked at the ACC for understanding psychopaths’ negative emotions and behaviours . Some individuals have less activation in this area, those with psychopathic traits show less responsiveness in the ACC in response to another's pain as the pain increases . In relation to this, psychopaths have reduced activation of the amygdala and the RACC/ventromedial prefrontal cortex in response to emotional words in the state of emotional memory model .

Testing

Iowa gambling task

Those with dysfunction in this area perform worse on the Iowa gambling task (IGT). It is made up of 4 decks of cards that have a different value of gain and loss. The player must pick from these decks 100 times and aim to win as much as possible. What the player does not know is that decks A+B have a higher value of gain and loss and decks C+D have a lower value of gain and loss. if the player were to keep picking from decks C+D they would finish the task with a larger sum of money than if they choose some or all from decks A+B. The idea of this task is to see if the player can learn from their mistakes and can inhibit the impulsion to win the bigger money. Those with dysfunction in the ACC often struggle with task either because they are too impulsive (lack of emotion regulation) or unable to detect their error (cognitive regulation).

Stroop task

The stroop task is a series of words that are colours, but are in a different colour in contrast to what the word says. Participants are ask to name the word or vice versa the colour of the word, the idea is to see if the participant can inhibit what they are not being asked. Reaction time is measured to estimate inhibitory control. Those dysfunction of the ACC can have abnormal reaction times and often they struggle with this task.

See also

Synapse

Neurotransmitter

MRI

FMRI

Go/No-go task