A 60-year-old man with frontotemporal dementia (FTD) shows marked disinhibition, perseveration, utilisation behaviour, and lack of empathy. Which frontal lobe circuit is primarily implicated in his disinhibition and social inappropriateness?

• A Dorsolateral prefrontal-subcortical circuit
• B Orbitofrontal-subcortical circuit ✓
• C Anterior cingulate-subcortical circuit
• D Mediodorsal thalamo-frontal circuit

Explanation

Three main prefrontal-subcortical circuits are clinically relevant: (1) Dorsolateral prefrontal (DLPFC) circuit — dysfunction causes executive dysfunction, cognitive inflexibility, working memory deficits; (2) Orbitofrontal circuit — dysfunction causes disinhibition, impulsivity, social inappropriateness, and changes in personality (as in this FTD patient); (3) Anterior cingulate circuit — dysfunction causes apathy, akinesia, and amotivation. Behavioural variant FTD predominantly affects orbitofrontal and medial frontal areas, explaining the disinhibition and lack of empathy.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.