Pupil size shows diminished increases on verbal fluency tasks in patients with behavioral-variant-frontotemporal dementia

Abstract

While behavioral variant frontotemporal dementia (bvFTD) is mainly associated with behavioral, social, cognitive, and emotional impairments, impairments in language can also be observed. We thus assessed whether linguistic processing can be assessed by pupillometry. We invited patients with bvTFD and control participants to perform a verbal fluency task, a category fluency task and, as a control task, to count aloud. During the three tasks, pupil size was monitored using eye-tracking glasses. Results demonstrated smaller pupil size on letter and category verbal fluency tasks, as well as during counting, in patients with bvFTD compared with control participants. However, larger pupil size was observed during verbal fluency tasks compared to counting in both patients with bvFTD and control participants. There were the no significant differences on pupil size between letter and category fluency tasks in any population. Finally, patients with bvFTD compared to control participants had lower verbal fluency. Taken together, these findings demonstrate how verbal fluency may decrease pupil size less in patients with bvFTD than controls, and how pupillometry can be used to follow linguistic processing in patients with frontal lobe impairments.