Inhibition processes are dissociable and lateralized in human prefrontal cortex

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• The prefrontal cortex (PFC) is crucial for executive functions, but its specific role in inhibition remains unclear.
• Previous lesion studies on inhibition have yielded inconsistent results.
• Inhibition, the ability to suppress prepotent responses, is a key executive function.

Purpose of the Study:

• To investigate the relationship between focal unilateral PFC lesions, inhibition, and fluid intelligence.
• To determine the precise neural substrates of inhibition using voxel-based lesion symptom mapping (VLSM).
• To explore whether different inhibitory tasks engage distinct PFC circuits.

Main Methods:

• Cognitive and neuroimaging investigations on patients with focal unilateral PFC lesions.
• Utilized the Hayling Part 2 and Stroop Colour-Word Tests to assess verbal inhibition.
• Employed voxel-based lesion symptom mapping (VLSM) to correlate lesion location with task performance, controlling for fluid intelligence.

Main Results:

• PFC patients showed significant impairments in inhibition on both the Hayling and Stroop tasks compared to healthy controls, even after accounting for fluid intelligence.
• Performance on the Hayling suppression measures was linked to the right lateral PFC, specifically the superior and middle frontal gyri.
• Performance on the Stroop task was associated with the left lateral PFC, specifically the superior and middle frontal gyri.

Conclusions:

• Inhibition is not a unitary function but comprises qualitatively different forms with distinct neural substrates in the PFC.
• The Hayling and Stroop tasks likely assess dissociable components of executive functions, mediated by lateralized PFC circuits.
• Findings have clinical implications for diagnosing and treating disinhibition impairments following PFC lesions, emphasizing the need for varied assessment tools and targeted treatments.