8 - cognitive control and inhibition Flashcards
what is cognition?
- basis for ‘intelligent’ behaviour
- overrides reflexive, habitual responses in favour of complex, long-term goals
- key neural structure in mammals: prefrontal cortex
what is the difference between cognitive control and executive function?
often used interchangeably
executive functions used for more specific components e.g. working memory
cognitive control has less clear separation of distinct subcomponents
features of cognitive control/executive functions
- top-down mental processes
- requires effort or attention
- core (e.g. WM) vs high-order (e.g. ToM) abilities
what is working memory?
holding information in mind and mentally working with it
what is cognitive flexibility?
changing perspectives or approaches to a problem, flexibly adjusting to new demands, rules, or priorities
requires or builds on other executive functions
measure using Wisconsin card sorting task
what is Wisconsin card sorting test?
measures cognitive flexibility
cards with different symbols and colours
participant presented with card, they have to decide which category of cards it fits into
receive feedback on whether it was correct or wrong
correct category changes at some point, participant has to adapt
key measure is perseveration errors (number of times participant kept choosing ‘old’ category)
what are current challenges with the Wisconsin card sorting test?
- neurological damage is unique in each patient
- studies attempt to identify more localised involvement
- solving task doesn’t only involve cognitive flexibility
what is inhibition?
controlling one’s attention, behaviour, thoughts and/or emotions to override a strong internal predisposition or external lure
some say simply strengthen specific thoughts and actions
others say we strengthen some and inhibit alternative actions and thoughts
how do response times effect inhibition?
shorter response time = impulsive, incorrect responses
longer response time = thoughtful, correct responses
successful inhibition is suppressing prepotent response, waiting for correct response to come
what is the key function of the frontal lobe?
to inhibit automatic and habitual behaviour
- seen in neurological studies on frontal lobe damage
- seen in utilisation behaviours (give object to patient with use, they use it even if they don’t need it)
what is the difference between directed and competitive inhibition?
directed - explicitly told not to do something
competitive - many actions competing and inhibiting one another
what are the core executive functions?
working memory
inhibitory control
cognitive flexibility
generally relate and connect each other in different ways, cannot be separated
what is behavioural inhibition?
stopping physical actions
what is cognitive inhibition?
stopping mental processes
inhibiting memories, thoughts, perceptions, emotions
what are types of behavioural inhibition?
deferred gratification (stop impulsive choice)
response inhibition (stop impulsive action)
reversal learning (allows for flexibility)
what is reaction time?
time between onset of stimulus and onset of response
varies across individuals and repetitions
what drives variability of reaction time?
the slope of the process
what is the neurophysiology of reaction time variability?
neurons in frontal cortex indicate that reaction times vary due to rate variability in slope of underlying process
before movement onset neuron sharply increases firing rate
difference is in the slope of the firing rate (process)
how is inhibition measured?
using behavioural tasks
e.g. go/NoGo task, stop-signal task
what is a Go / NoGo task?
participant needs to respond to some stimuli (Go stimuli), but not to others (NoGo stimuli)
measure reaction times and number of correct Go and NoGo trials
what are limitations of the Go/NoGo task?
easy task
general in terms of inhibition, not specific
what is the stop-signal task?
participants receive a go signal - “go” trial
occasionally receive a stop signal where they should refrain from responding - “stop” trial
key parameter is stop-signal delay (time between go and stop signal)
how does stop-signal delay effect response?
short delay is easier to inhibit because response not yet imminent
long delay is harder to inhibit because response is imminent
what is measured in the stop-signal task?
reaction times (of go trials and failed stop trials)
number of correct/error trials (% of correct and failed stops)
but never claps = 100% success rate on correct stops
can be used to calculate stop-signal reaction time (SSRT)
what is stop-signal reaction time a measure of?
reactive inhibition - how quickly participants can react to stop signal
includes all 3 components of stopping: stimulus detection, action selection, inhibition
what is the stop-signal reaction time?
the time it takes for an individual to successfully stop a planned action after stop signal is presented
what is the race model of stopping?
stopping can be modelled as a race between two processes:
- one representing response (“go process”)
- another representing inhibition (“stop process”)
process that reaches threshold first determines behaviour
how is the stop-signal reaction time estimated?
using “go” reaction time and stop-signal delay
what is reactive inhibition?
the ability to quickly react to the stop-signal
what is proactive inhibition?
the ability to adjust behaviour in anticipation of potentially having to inhibit a response
we can prepare to stop by exerting proactive control
how is proactive inhibition measured?
change in reaction time in Go trials
using stop-signal task, provide information on the probability of the stop-signal
what are clinical examples of impaired stopping?
Parkinson’s disease
Alcohol dependence
methamphetamine abuse
cocaine abuse
all see longer SSRTs
what happens in Parkinson’s disease?
- death of dopaminergic neurons
- severe motor symptoms
- longer SSRT
