Time estimation in healthy ageing and neurodegenerative basal ganglia disorders.

A decline in motor performance and timing performance is evident not only in clinical patient groups, e.g. with Parkinson's or Huntington's disease but also in normal ageing. Common to the mentioned groups is a deterioration in dopaminergic function of fronto-striatal brain circuits. These areas belong to a distributed network in the brain playing an important role in time perception and timing behaviour. Therefore, we measured time estimation performance in five groups of healthy young and healthy old participants, of patients with Parkinson's disease (PD), with presymptomatic and symptomatic Huntington's disease (HD). Participants were instructed to indicate by a precise button press when 1.2s had elapsed after stimulus onset. They received feedback after correct (within a specified time window) or incorrect responses. When compared to the young control group the performance in old participants, patients with Parkinson's, presymptomatic and symptomatic Huntington's disease was inferior, while differences were not noticed between the latter four groups. The data underline the importance of fronto-striatal circuits in the brain for time processing and time estimation. It is suggested that it is not the degree of dysfunction of the fronto-striatal dopamine system but rather the mere existence of a dysfunction, even if subtle, which is pivotal for a decline in timing performance. A time estimation task can serve as a useful tool to detect even faint changes in the integrity of the fronto-striatal dopamine system.