Disrupted Time Perception Underlies Motivational Disturbances in Huntington's Disease

Our sense of time is fundamental to interacting with the world in a goal-directed manner, with decisions underpinning goal pursuit utilising timing circuits in the seconds-to-minutes range. A reduction in goal-directed behaviour - apathy - is common in Huntington's disease (HD), but no work has examined whether altered time perception could be a contributing mechanism. We investigated whether timing deficits were evident in HD apathy. Genetically confirmed carriers of the HD mutation (premanifest to mild manifest disease, n = 39) and healthy controls (n = 20) performed a time production task with active (press) and passive (wait) modes of production, alongside clinical and behavioural measures. Overall, people with HD underproduced target times whilst controls performed in near-optimal manner. In HD, there were significant interactions between condition (press/wait) and both apathy and impulsivity (apathy × condition: t = -3.8, p = 0.0002; impulsivity × condition: t = -3.3, p = 0.001). This was driven by people with either of these behavioural disturbances producing shorter times in the passive condition, relative to people without these behaviours. Whilst global timing deficits were evident in HD, further differences were evident as a function of apathy and impulsivity, whereby people thought more time had passed than really had, specifically when passively waiting. Altered time perception when passively waiting may alter estimation of environmental reward rates and subsequent decisions of when to act. Overall, and demonstrated in human neurological disease, we show that timing processes and motivated behaviours are fundamentally linked.