cognitive control

Question 1

Liebe (2012)

Answer 1

• monkeys performing visual WM task
• simultaneous recording from lateral PFC and V4
• increased synchrony between theta phases in PFC and V4 during delay period
• stronger synchrony when monkeys successfully maintained info in WM / remembered stimulus
• provides explanation of mechanism for how info is shared between both areas during maintenance of WM
• therefore how PFC exerts cognitive control over lower areas

Question 2

Pasternak (2015)

Answer 2

• delayed match-to-sample task with random dot stimuli of varying motion coherence
• lesion to lateral PFC impaired ability of monkeys to remember direction of motion, but didn’t depend on motion coherence (i.e. stimulus properties)
• also more impaired for same stimulus in certain locations
  suggests PFC plays role in attending to stimuli and shifting attention to motion in other areas

Question 3

Postle (2006)

Answer 3

• retention of info in WM occurs alongside sustained activity in same brain regions responsible for representation of info in non-WM situations, so PFC is not simply a substrate for storage during WM
• instead, role of PFC is to employ control processes (e.g. attentional selection, flexible control etc) that are also required when performing WM task
• so PFC actively focuses attention on relevant sensory representation, selects info and performs executive functions necessary for cognitive processing of selected info

Question 4

Wallis (2001)

Answer 4

• single-cell recordings from PFC (dorsolateral, ventrolateral and orbitofrontal) of monkeys trained to use two abstract rules: indicate whether two images were same or different depending on current rule
• performed task with new images = shows general rule had been abstracted from previous experience
• 50% neurons showed higher activity for match rule and 50% for non-match = selective for specific rule
• ability to abstract rules from direct experience allows these rules to be applied to general situations = intelligent behaviour

Question 5

Asaad (2000)

Answer 5

• recordings from PFC neurons in 2 monkeys during 3 types of task: spatial, object and associative
• for many PFC neurons, activity was modulated by task being performed e.g. different baseline activity
• some neurons always active to same object regardless of task, others active to object only when certain behavioural response was required (so both sensory/perceptual and higher-level decision-making processes)
• increased neuronal activity in delay during object task: could represent impending choice / preparation, or could be inhibition of actions involved in the associative task for same object

Question 6

Milner 1963 / Dias 1997

Answer 6

• impairment on WCST is classic sign of PFC damage in humans
• unable to exert cognitive control / flexibly alter their responses to same stimuli depending on which rule is currently in effect
• Dias = primate analogue

Question 7

Miller (2000)

Answer 7

• humans don’t just reflexively react to immediate sensory info
• we have complex behaviours geared towards internally-generated and often far-removed goals
• mechanisms sculpted through experience/learning control lower-level sensory/motor operations for higher purpose
• forms basis of intelligent behaviour
• PFC must extract goal-relevant features of experiences that can be applied to future / abstract situations
• while HC binds stimuli into long-term memories consisting of specific episodes (e.g. Squire & Zola-Morgan 1991), PFC represents regularities in goals between different episodes = flexibility
• VTA dopaminergic neurons encode unexpected reward / reward prediction / prediction error so encode for associative learning
• DA influx affects plasticity by strengthening associative connections, and protects them against interference from distractors (maintain goal)
• PFC provides excitatory bias signals to other brain structures to flexibly guide flow of activity along task-relevant neural pathways (link to competition bias theory)

Question 8

Miller 1996

Answer 8

• sustained activity to sample in PFC may enhance responses to its repetition in inferior temporal cortex
• PFC therefore provides excitatory bias signals to other brain structures to flexibly guide flow of activity along task-relevant neural pathways (link to competition bias theory)

Question 9

Ragland (2015)

Answer 9

• fMRI and schizophrenic patients
• can engage VLPFC to provide control over semantic encoding of individual items
• but impaired at engaging DLPFC to provide more general control over all task items and only encode those that are task-appropriate
• therefore didn’t display improved episodic memory for target vs non-target items (whereas controls did)
• highlights differential roles for VLPFC and DLPFC in cognitive control

Question 10

Levy (2011)

Answer 10

• fMRI of right vlPFC
• inferior frontal junction (IFJ) = detection of behaviourally relevant stimuli (stopping and reflexive orienting)
• posterior areas of VLPFC = action updating
• other VLPFC areas = motor inhibition
• so has rich functional heterogeneity to allow for complex executive function

Question 11

Anderson (2001; 2016)

Answer 11

• DLPFC responsible for inhibitory control over behaviour via retrieval suppression (top-down modulation of HC activity) - although Aron (2007) argued against existence of this kind of inhibition
• form of executive control, prevents activation of HC episodic memories
  process also implicated in forgetting

Question 12

Curtis & D’Esposito (2003)

Answer 12

DLPFC activation reflects top-down biasing control over posterior lower-level regions that store sensory representations = cognitive control during WM task

Question 13

Wager (2004)

Answer 13

fMRI showed lateral PFC more active when performing tasks that demand cognitive flexibility

Question 14

Damasio (1994)

Answer 14

• phineas gage: ventromedial PFC / OFC damage from tamping iron, loss of cognitive control
• impaired rational decision-making and processing of emotion = inappropriate behaviour in social situations (dysexecutive syndrome)
• impulsive, irresponsible
• but good performance on perceptual, memory and motor skills, and normal IQ

Question 15

Schoenbaum (2006)

Answer 15

• rats and outcome devaluation: food devaluated by adding poison
• despite showing they had learnt association between food and nausea (so had learned devaluation the same as normal rats), rats with OFC lesions still tried to get food
• inability to use stored memory of emotional event / outcome expectancies to guide action

Question 16

Bechara (1997)

Answer 16

• iowa gambling task (use emotional responses to learn rule and pick from decks C and D, not A and B)
• either OFC or amygdala lesion disrupts SCRs in this task
• patients can’t use emotional value of wins and losses to guide behaviour and win money in task. need both amygdala and OFC to do this

Question 17

Stokes (2013)

Answer 17

• used dynamic pattern analysis to determine how PFC establishes, maintains and uses flexible cognitive states for task-dependent decision making
• coding initially reflected physical properties of choice stimulus, then differentiated between two alternative decision values: “go” vs “no-go”
• neuronal activity in delay period represents distinct neurophysiological state triggered during cue processing, where the tuning profile of PFC neurons have temporarily been set according to task demands i.e. tuned to classify each choice stimulus as “go” or “no-go” response signal
• so PFC processes input as function of task relevance
• can switch between behavioural responses depending on neuronal activation in PFC which is dictated by task demands

Question 18

McGuire (2010)

Answer 18

• lateral PFC fMRI activity correlated with costs (e.g. computationally demanding, subjectively effortful) in cue-switching task
• individual differences so highest LPFC activity in subjects who had highest aversion to cognitively demanding tasks
• internal costs may represent degree to which brain regions responsible for control / executive function mechanisms are recruited
• so level of LPFC activity could predict how effortful subjects will report task as?
• human decision-making involves balance of motive to maximise gains and motive to minimise decision costs e.g. effort-accuracy tradeoffs
• cognitive misers! (Taylor 1981)
• demonstrated in simple, highly controlled lab task. how does this relate to complex real life decisions?
• looked at avoidance, but how does internal cost drive strategy selection? probably interesting IDs here too e.g. might choose strategy best suited to their personal abilities

Question 19

Edwards (2010)

Answer 19

• focused cognitive control training in Sz: direct encoding of contextual cues and updating response goals in accordance with cue information
• before training = impaired ability to use contextual cue info and reduced cue-related activity in LPFC
• after training = more able to use this info (similar to controls)
• suggests focused strategy training improves cognitive task performance in Sz by changing dynamics of activity in control-related brain regions
• shift in activity in LPFC = more proactive pattern (less reactive strategy)
• also pre-training results were similar to results from healthy older adults = shift from proactive to reactive control could be final common pathway that results from various etiologies/pathologies?

Question 20

Braver (2013)

Answer 20

• dual mechanisms framework for cognitive control
• proactive = sustained and anticipatory maintenance of goal-relevant info with LPFC which enables optimal cognitive performance (early selection)
• reactive = transient, stimulus-driven goal reactivation which activates LPFC due to episodic associations etc