NRSC 2249 - Cognitive Control

mammalian PFC

• present in all mammals, but larger in primates

  • more expansion in white matter (axons) than gray (cell bodies)

• human-unique cognitive capabilities more about connections than size

adult human PFC

• massively interconnected network:

  • motor, perceptual, limbic (memory/emotion)

  • reciprocal with parietal and temporal

  • thalamus → PFC → basal ganglia, cerebellum, brainstem nuclei

  • cortical and subcortical areas

• coordinating and integrating information

subdivisions of the PFC

lateral prefrontal, frontal pole, orbitofrontal, medial frontal

lateral PFC

• executive function: strategic planning, complex decisions, multiple goals

• behavioral control: behavioral rules, instinct inhibition, selective attention

• abstract knowledge

frontal pole

• complex processes: abstract thinking, decision-making, integrating information, long-term planning

• social cognition: understanding other perspectives, self-reflection

• hypothetical scenarios

• most anterior in frontal lobe

orbitofrontal cortex

• emotional regulation: reward vs. punishments, emotional value of stimuli, impulse control

• social behavior: empathy, social nuances, social interactions

medial frontal cortex

• ACC: selective attention, error detection, risk vs. reward

• rational functioning: logical thinking, problem-solving

• emotional regulation: empathy, emotional awareness and processing

ventral-dorsal gradient

• mirrors what (ventral) vs how (dorsal) distinctions of visual pathways

  • ventral: details about objects

  • dorsal: planning and executing actions

• allows for integration of cognitive processes

• reflects hierarchical organization of brain

anterior-posterior gradient

• anterior: abstract concepts

• posterior: concrete tasks

  • posterior PFC: working memory

  • PMA: translation of abstract intentions into actions

lateral-medial gradient

• source of information affecting working memory

  • lateral: external cues, integrating external information

  • medial: internal drives, emotional states

PFC lobotomy

• aimed to treat illnesses such as schizophrenia, bipolar disorder, epilepsy

• patients experienced less spontaneity, responsiveness, emotional dullness, narrowed intellectual capacity

  • emotionally blunted, impacted IQ

frontotemporal dementia

• degeneration (atrophy) of frontal and temporal lobes

  • more pronounced sulci, shrunken gyri

• significant changes to personality and social behaviors

• associated with various aphasias

behavioral variant FTD (bvFTD)

• most prevalent form of FTD

• changes in personality, apathy, loss of empathy, disinhibition, deficits in complex thinking

• may involve progressive semantic dementia

PFC lesion studies

• focal injuries to prefrontal cortex

• often mirror behavior of bvFTD

• may be difficult to diagnose based on everyday

common deficits in cognitive control

• bilateral lesions result in severe impairments

• deficits in cognitive control / executive function associated with: depression, schizophrenia, OCD, ADHD

• external factors: stress, emotional distress, poor health

• drug addiction disrupts PFC functioning

Wisconsin Card Sort

• psychological assessment tool used to evaluate cognitive flexibility and problem-solving

• participants asked to sort cards based on a changing rule from trial and error

• impairment with damage to dorsolateral and superior medial PFC

n-back test

• participants required to press a button upon repeated stimulus: requires maintenance and refreshing of working memory

• increase in LPFC activity with increase in complexity

  • role in active manipulation of info in working memory

maintenance (working memory)

holding task-relevant information in awareness

manipulation (working memory)

interacting with held information, working towards a goal

working memory

• hindered with damage to the LPFC

• maintenance of task-relevant info and manipulation towards goal

delayed-response task

• used to measure working memory

• monkeys must remember location of food after a delay without external cues (working)

• association of a consistent visual cue requires LTM

  • not impaired with damage to the LPFC

what-where cells

• specialized cells within the LPFC (about half of cells)

  • what: respond to specific objects during delay

  • where: respond to specific locations during delay

neural basis of delayed-response task

• lateral PFC sustains representation of task goal

  • rises during encoding, remains high during delay, extends to retrieval period

• temporal cortex rises earlier and drops during delay period

rule-switching (working memory)

• responsiveness of PFC cells is adaptable: same cells can shift responsiveness to new set of stimuli

• distinction from IT cortex: maintain selectivity regardless of task demands

decisions can be…

• goal oriented: based on assessment of outcome

• habitual: independent of immediate rewards

theories about decision making can be…

• normative: how people ought to make decisions, often fails to predict actual behavior

• descriptive: what people do vs. what they should do

decision making can be…

• model-based: based on internal representations of the world

• model-free: direct stimulus-response mappings

external factors of decision-making

commodity, quantity, delay, risk, ambiguity, cost

internal factors of decision-making

motivation, patience, risk attitude, ambiguity attitude

temporal discounting

• tendency in decision-making to value immediate rewards over future ones

  • varies widely among individuals

expected value (EV)

average outcome of a risky event when considering all possible outcomes and probabilities

neural basis of value (decision-making)

• patients with OFC damage exhibits damage in decision-making

• not willing to wait for better rewards, prefer immediate outcomes

brain structures associated with reward

• basal ganglia, hypothalamus, amygdala

• dopamine: substantia nigra, ventral regimental area

  • related more to the anticipation/expectation of a reward than the actual amount or magnitude of reward

reward prediction error (RPE)

• thought to be encoded by DA neurons in SN and VTA

• difference between expected and received rewards

  • guides learning and decision making based on rewards

• diminished response when expectation aligns with outcome

GABA neurons (reward)

• sends inhibitory signal to DA neurons

• signals reward expectancy

challenge to DA RPE

• DA activity could code consequences of prediction and learning: reflect salience/desirability

  • valence neurons (VTA): increase activity to stimuli predictive of a reward, similar to RPE

  • salience neurons (SN): increase activity with reinforcement probability

flexibility

• ability to adapt to changes in the environment and update action plans in accordance

• relies on PFC, ACC, basal ganglia, and thalamus

filtering task-relevant information

• choosing what to pay attention to and ignoring irrelevant tasks

• requires focusing attention on perceptual features or informarion

• lateral PFC

inhibitory control

• ability to change when about to take an action

  • activity in right inferior frontal cortex when about to abort a planned response for successful and failed stop

  • activity in motor cortex for go and failed stop, successful stop peaks later

ACC: executive attention hypothesis

• MFC and ACC serve as top level of attentional hierarchy, coordinating activity across attention systems

• empirical support: increased activity during divided attention, changes as attention demands decrease

• critiques: no specification of recruitment of ACC or kinds of representations, unclear how is used for cognitive control

ACC: error detection hypothesis

• ACC is involved in monitoring behavior through error detection to increase or reallocate cognitive control

• empirical support: activity correlated with occurrence of errors

• critiques: activity not limited to errors, feedback-negativity could be unexpected outcome rather than error

ACC: response conflict hypothesis

• ACC and MFC assess response conflict, which is high in unfamiliar or complex situations

• empirical evidence: LPFC reflects degree of difficulty for selection/task; ACC reflects degree of response conflict