Mapping causal links between prefrontal cortical regions and intra-individual behavioral variability

Area of Science:

• Neuroscience
• Cognitive Science
• Primate Behavior

Background:

• Intra-individual behavioral variability increases with aging and neuropsychological disorders.
• The specific brain regions causally linked to heightened behavioral variability remain largely unknown.
• Understanding these neural underpinnings is crucial for addressing cognitive impairments.

Purpose of the Study:

• To investigate the causal role of distinct frontal cortical regions in modulating response time (RT) variability during decision-making.
• To determine how lesions in specific prefrontal areas affect cognitive flexibility and RT variability.
• To elucidate the neural basis of behavioral variability in rule-guided tasks.

Main Methods:

• Utilized a cohort of 21 macaque monkeys performing a rule-guided decision-making task.
• Implemented selective bilateral lesions in various frontal cortical regions: anterior cingulate cortex (ACC), dorsolateral prefrontal cortex, frontopolar cortex, mid-dorsolateral prefrontal cortex, posterior cingulate cortex, and orbitofrontal cortex (OFC).
• Assessed cognitive flexibility and quantified response time variability post-lesion.

Main Results:

• Lesions in the ACC and dorsolateral prefrontal cortex impaired cognitive flexibility but diminished RT variability.
• Lesions in the frontopolar and mid-dorsolateral prefrontal cortex had no significant effect on cognitive flexibility or RT variability.
• Posterior cingulate cortex lesions increased RT variability without affecting cognitive flexibility.
• Orbitofrontal cortex (OFC) lesions uniquely caused both cognitive flexibility deficits and increased RT variability.

Conclusions:

• Demonstrated dissociable roles of frontal cortical regions in regulating behavioral variability.
• Suggests OFC lesions impair evidence accumulation for decision-making, increasing variability.
• Proposes ACC lesions lead to impulsive responses due to a lowered decision threshold, decreasing variability.