Frequent Terms in Neuroscience
From time to time in Buddhsim 1-2-3 classes, we have discussed how neuroscientists are increasing their understanding of Buddhist practices, especially chanting and meditation, and how they might affect the brain.
As a gloss on frequent terms, Dharma Friend Akira Sumida assembled these definitions. Akira also supplied the content for the posting “Your Brain on Nembutsu.” See the short gloss below and then scroll down for more detailed discussion.
Short Definition of Terms
ACC (Anterior Cingulate Cortex)
Emotions, motivation, effort, attention allocation, reward anticipation, decision-making, ethics and morality, impulse control (e.g. performance monitoring and error detection), and emotion.
AG (Angular Gyrus)
Complex language functions (reading, writing, and interpuretation), attention, awareness, memory retrival.
dlPFC (Dorsolateral Prefrontal Cortex)
Working memory and selective attention, risky and moral decision making, overriding prepotent emotional biases.
mPFC (Medial Prefrontal Cortex)
Excutive function, memory, and attention: planning complex cognitive behavior, personality expression, decision making, moderating social behavior, concrete rule learning, and rule learning at higher levels of abstraction.
PPC (Posterior Parietal Cortex)
Attention, motor function, language, understanding of numbers and arithmetic.
SMG (Supramarginal Gyrus)
Perception of space and limbs location, identifying postures and gestures of other people, emotional regulation, empathy.
Expanded Definition of Terms
Anterior Cingulate Cortex (ACC)
The ACC 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.
It is also involved in certain higher-level functions, such as attention allocation, reward anticipation, decision-making, ethics and morality, impulse control (e.g. performance monitoring and error detection), and emotion.
The most basic form of ACC theory states that the ACC is involved with error detection. 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.
The ACC area in the brain is associated with many functions that 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 is supported by some evidence, in that it seems to be the case that, when subjects' responses are not congruent with actual responses, a larger error-related negativity (ERN) is produced.
Angular Gyrus (AG)
Angular gyrus is significance in transferring visual information to Wernicke's area, in order to make meaning out of visually perceived words. It is also involved in a number of processes related to language, number processing and spatial cognition, memory retrieval, attention, and theory of mind.
The angular gyrus is the part of the brain associated with complex language functions (i.e. reading, writing and interpretation of what is written). Lesion to this part of the brain shows symptoms of the Gerstmann syndrome: effects include finger agnosia, alexia (inability to read), acalculia (inability to use arithmetic operations), agraphia (inability to copy), and left-right confusion.
Attention: The right angular gyrus has been associated with spatiovisual attention toward salient features. It may allocate attention by employing a bottom-up strategy which draws on the area’s ability to attend to retrieved memories. For example, the angular gyrus plays a critical role in distinguishing left from right, by integrating conceptual understanding of the language term "left" or "right" with its location in space. Furthermore, the angular gyrus has been associated with orienting in three dimensional space, not because it interprets space, but because it may control attention shifts in space.
Awareness: The angular gyrus reacts differently to intended and consequential movement. This suggests that the angular gyrus monitors the self's intended movements, and uses the added information to compute differently as it does for consequential movements. By recording the discrepancy, the angular gyrus maintains an awareness of the self.
Memory Retrieval: Activation of the angular gyrus shows that not only does it mediate memory retrieval, but also it notes contradictions between what is expected from the retrieval, and what is unusual. The angular gyrus can access both content and episodic memories, and is useful in inferring from these the intentions of human characters.Furthermore, the angular gyrus may use a feedback strategy to ascertain whether a retrieval is expected or unusual.
Out-of-Body Experiences: Recent experiments have demonstrated the possibility that stimulation of the right angular gyrus is the cause of out-of-body experiences. Stimulation of the left angular gyrus in one experiment caused a woman to perceive a shadowy person lurking behind her. The shadowy figure is actually a perceived double of the self. Another such experiment gave the test subject the sensation of being on the ceiling. This is attributed to a discrepancy in the actual position of the body, and the mind's perceived location of the body.
Dorsolateral Prefrontal Cortex (dlPFC)
The dorsolateral prefrontal cortex is a region of the frontal lobes that is most typically associated with executive functions including working memory and selective attention. Through connections with parietal cortex, dorsolateral prefrontal cortex is a key node in dorsal attention networks that support basic cognitive selection of sensory information and response. Although this region does not project directly to emotion generators, it may influence emotional reactivity by altering higher-order perceptual attention systems.
The DLPFC is known for its involvement in the executive functions, which is an umbrella term for the management of cognitive processes, including working memory, cognitive flexibility, and planning. A couple of tasks have been very prominent in the research on the DLPFC, such as the A-not-B task, the delayed response task and object retrieval tasks. The behavioral task that is most strongly linked to DLPFC is the combined A-not-B/delayed response task, in which the subject has to find a hidden object after a certain delay. This task requires holding information in mind (working memory), which is believed to be one of the functions of DLPFC.
The DLPFC is involved in both risky and moral decision making; when individuals have to make moral decisions like how to distribute limited resources, the DLPFC is activated This region is also active when costs and benefits of alternative choices are of interest. Similarly, when options for choosing alternatives are present, the DLPFC evokes a preference towards the most equitable option and suppresses the temptation to maximize personal gain.
Recent studies suggest its specific involvement in overriding prepotent emotional biases, such as when delaying gratification or making utilitarian decisions in the context of moral dilemmas. The dlPFC is also activated by unfair offers in the ultimatium game (UG), which subjects are more likely to accept when dlPFC activation exceeds anterior insula activation .This has led to the hypothesis that UG decisions, and difficult social decisions more generally, often involve competition between emotional processing and higher-level controlled or deliberative processing that bias decision making in opposite ways. Emotional processes are driven by the subcortical, limbic, and paralimbic structures, whereas the deliberative processes rely on the anterior and dorsolateral regions of prefrontal cortex, as well as areas of posterior parietal cortex. Further evidence in support of the a role for the dlPFC in social decision making is provided by studies showing that application of repetitive transcranial magnetic stimulation (rTMS) to the dlPFC influences decision making in the UG. Finally, dlPFC activation is also associated with the choice to defect in the prisoners dilema game, suggesting that most people may in fact have a prepotent emotional bias to cooperate in the game.
Medial Prefrontal Cortex (MPC)
The medial prefrontal cortex is a midline frontal region typically associated with self-processing and other-processing. Dorsomedial prefrontal cortex, working with other structures, is considered to be a necessary node in the default mode network that enables humans to project themselves outside the present moment and focus on things other than the self in the here-and-now. Consistent with this idea, dorsomedial prefrontal cortex is often active during tasks in which participants must focus on the perspectives and feelings of other people. The dorsomedial prefrontal cortex is also active during certain types of emotion regulation (eg, reappraisal), which may reflect the fact that reappraisal requires people to reconsider the perspectives of others and the significance of emotional situations.
Left to our own devices, we tend to react with “low road” solutions, because we’re uncomfortable and we want to do something now. However, scientists are discovering that it is possible to train the brain to prefer “high road” solutions through practices that favor the part of the mPFC that are associated with deliberative choices rather than the part associated with habits and emotions.
mPFC has been shown to play a fundamental role in a wide range of social cognitive abilities such as self-reflection, person perception, and theory of mind/mentalizing. This involvement of mPFC in social cognition and interaction has lead to the notion that mPFC serves as a key region in understanding self and others. It is also involved in feedback categorization, performance monitoring, and task monitoring, and may contribute to the online regulation of reinforcement learning (RL) parameters that would affect decision-making processes.
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 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.In The Astonishing Hypothesis, Francis Crick identifies the anterior cingulate, to be specific the anterior cingulate sulcus, as a likely candidate for the center of free will in humans. Crick bases this suggestion on scans of patients with specific lesions that seem to interfere with their sense of independent will, such as alien hand syndrome.
Posterior Parietal Cortex (PPC)
The posterior parietal cortex receives input from a collection of sensory areas as well as a variety of other regions of the brain, and is thought to integrate that input to facilitate the execution of functions that require diverse information. It has been associated with a number of these functions, which are sometimes called "higher-order" functions; it is probably best known, however, for its role in attention.
Through attempts to find the brain regions that facilitate attention, researchers have identified two attention-related networks that involve the posterior parietal cortex; these are termed the dorsal and ventral fronto-parietal systems. The dorsal system is thought to be involved with what is known as "endogenous attention," which involves attention that is directed based on individual goals or desires. For example, if you are attempting to focus your attention to read this article, you are utilizing endogenous attention.
The ventral system seems to be involved more in what is termed "exogenous attention," or attention that is directed towards external stimuli that are not being attended to by endogenous attentional processes. For example, if you were reading this article in a library and someone a few tables over shouted, breaking the complete silence of the room, you would suddenly and reflexively direct your attention to the person who shouted. This type of attention is not associated with your own goals or desires, and falls under the rubric of exogenous attention.
The importance of the posterior parietal cortex to attention is perhaps best exemplified by a condition that can occur after damage to the posterior parietal cortex known as hemispatial or contralateral neglect. Hemispatial neglect is most frequently associated with damage to the posterior parietal cortex in the right cerebral hemisphere (due to stroke, head trauma, etc.), after which the patient ceases to devote attention to the left side of their body and visual field. These patients can act as if they don't perceive anything in a certain part of their visual field; if asked to draw a picture, they will often not include a significant portion (up to half) of the item drawn, they may eat only about half of the food off of a plate, and shave or put makeup on only half of their face. Some patients may even deny that part of their body on the neglected side is theirs in an attempt to reject the idea that they are suffering from a neurological condition.
The posterior parietal cortex is also believed to be involved in some aspects of motor function, such as planning movements and integrating visual information with movement to facilitate actions like reaching and grasping. Additionally, the posterior parietal cortex is thought to be involved in language as well as the ability to understand numbers and arithmetic. Thus, its functions span a large spectrum ranging from attention to movement to number processing.
Supramarginal Gyrus
The supramarginal gyrus is part of the somatosensory association cortex, which interprets tactile sensory data and is involved in perception of space and limbs location. It is also involved in identifying postures and gestures of other people, and is thus a part of the mirror neuron system.
The right-hemisphere supramarginal gyrus appears to play a central role in controlling our empathy towards other people. When this structure isn't working properly or when we have to make very quick judgments, our empathy becomes severely limited. Research has shown that disrupting the neurons in the right supramarginal gyrus causes humans to project our emotions on others, inhibiting our ability to be empathetic. In addition, this disruption also causes people to be more egocentric, mainly because they aren't able to perceive the emotions of those around them. Both the left and right supramarginal gyri of healthy, right-handed individuals are shown to be active when making phonological word choices. Individuals who had lesions to the left hemisphere had more difficulty than those with lesions to the right hemisphere, reinforcing the dominance of the left hemisphere in language.
Note: In most cases definitions are pulled from Wikipedia, referenced October 2019.