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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
