Poster Session 05 Program Schedule
02/15/2024
02:30 pm - 03:45 pm
Room: Shubert Complex (Posters 1-60)
Poster Session 05: Neuropsychiatry | Addiction/Dependence | Stress/Coping | Emotional/Social Processes
Final Abstract #47
Linking motivational disturbances and behavioural rigidity in frontotemporal dementia
Kristina Horne, The University of Sydney, Sydney, Australia
Rebekah Ahmed, The University of Sydney, Sydney, Australia
Olivier Piguet, The University of Sydney, Sydney, Australia
Muireann Irish, The University of Sydney, Sydney, Australia
Category: Dementia (Non-AD)
Keyword 1: apathy
Keyword 2: motivation
Keyword 3: dementia - other cortical
Objective:
Individuals with frontotemporal dementia (FTD) develop increasingly rigid and inflexible patterns of behaviour, manifesting in the excessive pursuit of highly specific and perseverative compulsions and routines. This can include idiosyncratic fixations such as clockwatching and timekeeping, or the emergence of intense or obsessive interests such as a preoccupation with colours, numbers or puzzles. Paradoxically, these changes coincide with profound motivational disturbances such as apathy and anhedonia, which lead to a marked decline in goal-directed behaviour. As such, individuals tend to excessively pursue certain interests or routines at the expense of other, more adaptive behaviours, presenting a challenge for caregivers.
To reconcile these seemingly conflicting patterns of behaviour, we recently proposed that motivational changes may potentiate behavioural rigidity in FTD due to striatally-mediated alterations in reward processing. Here, we present the first study to investigate the link between these symptoms, using converging behavioural and neural approaches.
Participants and Methods:
We obtained carer-report questionnaires for 71 participants with FTD (26 semantic dementia [SD], 45 behavioural variant FTD [bvFTD]). We derived a novel, data-driven index of behavioural rigidity using existing items on the Cambridge Behavioural Inventory-Revised. We used linear regressions to explore the relationship between the severity of carer-rated rigidity symptoms with apathy and anhedonia symptoms and whether this differed between diagnostic groups. Furthermore, we used whole-brain voxel-based morphometry (VBM) on a subgroup of 55 participants who underwent neuroimaging (36 bvFTD, 18 SD) to determine the neural substrates underpinning behavioural rigidity at the transdiagnostic level.
Results:
Apathy and anhedonia were significant predictors of carer-reported rigidity, such that individuals with greater motivational disturbance were more inflexible in their behaviour. While the relationship between apathy and rigidity was comparable across groups, the role of anhedonia was unique to SD, indicating that distinct mechanisms contribute to rigidity in each diagnostic group. Critically, VBM analyses revealed a network of predominantly right sided frontostriatal regions in which reduced grey matter intensity was associated with increased rigidity. This included regions typically associated with reward processing, memory and semantics such as the nucleus accumbens, hippocampus and temporal lobe.
Conclusions:
In keeping with the proposed model, our findings provide behavioural and neural evidence demonstrating a link between alterations in primary reward and motivational pathways and the emergence of rigid and inflexible behaviours in FTD. These findings can be understood within the existing effort-based decision-making for reward framework, as the relationship between apathy and rigidity likely reflects the avoidance of effort required to deviate from established routines or to generate alternative ideas. In contrast, the link between anhedonia and rigidity in SD likely reflects an alteration in semantic knowledge of the inherent reward value of behaviours. As the first study to investigate the relationship between these debilitating symptoms, our findings hold important implications for the understanding and management of behavioural changes in FTD.
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