2 Neuroscience2.7 Neural circuits
2.7.1.14 Executive function, hypofrontality and impulsivity
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Written by Resident Doctor Committee · Published
Components of executive function
Process | What it does | Failure |
|---|---|---|
Inhibition | Withholds or cancels dominant responses | Acting before checking |
Working memory updating | Holds relevant information and replaces outdated content | Losing a task sequence |
Cognitive flexibility | Changes set with context or feedback | Persisting with an obsolete rule |
Perseveration is failure to abandon a response or rule once it no longer applies. It is a frontal lobe sign of lost prefrontal cognitive flexibility.
Frontal regions
Region | Contribution | Damage |
|---|---|---|
Dorsolateral prefrontal | Maintains goals and rules, organises steps | Poor organisation despite knowing the goal |
Orbitofrontal | Updates value after feedback | Repeated maladaptive choices |
Ventromedial prefrontal | Integrates reward, bodily state and social consequences | Poor everyday judgement despite normal testing |
Hypofrontality
Hypofrontality means reduced frontal activation, blood flow or metabolism relative to a defined comparison.
Ingvar and Franzén described reduced frontal blood flow in schizophrenia in 1974.
In schizophrenia it is the most replicated regional blood flow deficit: the dorsolateral prefrontal cortex fails to activate during executive tasks.
Task, baseline, performance and medication all affect the signal, and similar findings occur in other disorders.
Forms of impulsivity
Form | Behaviour | Probe |
|---|---|---|
Impulsive action | Premature responding | Reaction time or continuous performance tasks |
Impaired stopping | Failure to cancel an initiated action | Stop signal task |
Impulsive choice | Preference for smaller immediate rewards | Delay discounting |
These three forms correlate imperfectly, so normal stopping does not imply normal delay tolerance.