Inhibitory dysfunction in frontotemporal dementia: A review

Failure of inhibitory control is an early and consistent feature in patients suffering from frontotemporal dementia (FTD). This appears because of their pervasive ventromedial prefrontal atrophy - particularly in the orbitofrontal cortex - which has been linked to inhibitory dysfunction in studies on human and monkey lesions. However, the range of measures currently available to assess inhibitory processes in FTD is limited, and, as such, inhibitory dysfunction in FTD remains relatively underexplored. Subjective caregiver questionnaires are useful for defining disinhibition as it manifests behaviorally; however, endorsement of symptoms can vary largely across patients as it is contingent on the perceptiveness of the caregiver. The few objective neuropsychological tasks that tap directly into inhibitory functioning have potential, although they mostly rely on intact language and semantics, which can confound performance in FTD patients. An emergent possibility is to explore inhibitory functioning in FTD through nonverbal experimental tasks. Adaptation of such experimental tasks into clinical tools is a promising avenue for exploring one of the earliest behavioral features in FTD patients and concomitantly tap into their prevalent orbitofrontal cortex dysfunction. We suggest that improved characterization of early inhibitory dysfunction may facilitate more accurate diagnosis of FTD.