Establishing the link between motivational disturbances and behavioural rigidity in frontotemporal dementia

Kristina Horne; Rebekah M Ahmed; Olivier Piguet; Muireann Irish

doi:10.1111/ene.16132

Establishing the link between motivational disturbances and behavioural rigidity in frontotemporal dementia

Eur J Neurol. 2024 Feb;31(2):e16132. doi: 10.1111/ene.16132. Epub 2023 Nov 7.

Authors

Kristina Horne^{1

2}, Rebekah M Ahmed^{1

3

4}, Olivier Piguet^{1

2}, Muireann Irish^{1

2}

Affiliations

¹ The University of Sydney, Brain and Mind Centre, Sydney, New South Wales, Australia.
² The University of Sydney, School of Psychology, Sydney, New South Wales, Australia.
³ The University of Sydney, School of Medical Sciences, Sydney, New South Wales, Australia.
⁴ Memory and Cognition Clinic, Department of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia.

PMID: 37933881
DOI: 10.1111/ene.16132

Abstract

Background: Rigid and inflexible behaviours are common in frontotemporal dementia (FTD), manifesting in compulsive pursuit of specific interests, routines, and rituals. Paradoxically, these changes occur alongside profound motivational disturbances including apathy and anhedonia. While posited to be related, no study to date has explored the link between motivational changes and behavioural rigidity in FTD.

Methods: Carer ratings for 71 FTD participants (26 semantic dementia [SD], 45 behavioural variant [bvFTD]) were obtained on the Dimensional Apathy Scale (apathy), the Snaith-Hamilton Pleasure Scale (hedonic tone) and the Cambridge Behavioural Inventory-Revised (CBI-R; behavioural changes). A rigidity index was created from existing items on the CBI-R. Whole-brain voxel-based morphometry was used to explore associations between rigidity and grey matter intensity in the combined FTD group.

Results: Behavioural rigidity was significantly related to apathy severity (r = 0.57) and decreased hedonic tone (r = -0.36) in the combined FTD group. Multiple linear regression revealed a significant diagnosis × hedonic tone interaction (β = -1.40), whereby lower hedonic tone predicted rigidity in SD (r = -0.65) but not in bvFTD (r = -0.18). In contrast, the relationship between rigidity and apathy did not differ between the groups (β = -0.42). At the neural level, rigidity correlated with degeneration of predominantly right-sided frontostriatal structures including, notably, the nucleus accumbens.

Conclusions: As the first study to demonstrate a link between motivational changes and behavioural rigidity in FTD, our findings have important clinical implications. By identifying candidate mechanisms of behavioural rigidity, our findings can inform targeted interventions to manage inflexible patterns of thought and behaviour in daily life.

Keywords: anhedonia; apathy; frontotemporal dementia; inflexibility; semantic dementia.

MeSH terms

Apathy*
Brain
Frontotemporal Dementia* / complications
Frontotemporal Dementia* / diagnosis
Gray Matter / diagnostic imaging
Humans
Motivation
Neuropsychological Tests

Abstract

MeSH terms

Grants and funding