Processing of temporal information and the basal ganglia: new evidence from fMRI.

Temporal information processing is a fundamental brain function, which might include central timekeeping mechanisms independent of sensory modality. Psychopharmacological and patient studies suggest a crucial role of the basal ganglia in time estimation. In this study, functional magnetic resonance imaging (fMRI) was applied in 15 healthy right-handed male subjects performing an auditory time estimation task (duration discrimination of tone pairs in the range of 1,000-1,400 ms) and frequency discriminations (tone pairs differing in pitch, around 1,000 Hz) as an active control task. Task difficulty was constantly modulated by an adaptive algorithm (weighted up-down method) reacting on individual performance. Time estimation (vs rest condition) elicited a distinct pattern of cerebral activity, including the right medial and both left and right dorsolateral prefrontal cortices (DLPFC), thalamus, basal ganglia (caudate nucleus and putamen), left anterior cingulate cortex, and superior temporal auditory areas. Most activations showed lateralisation to the right hemisphere and were similar in the frequency discrimination task. Comparing time and frequency tasks, we isolated activation in the right putamen restricted to time estimation only. This result supports the notion of central processing of temporal information associated with basal ganglia activity. Temporal information processing in the brain might thus be a distributed process of interaction between modality-dependent sensory cortical function, the putamen (with a timing-specific function), and additional prefrontal cortical systems related to attention and memory. Further investigations are needed to delineate the differential contributions of the striatum and other areas to timing.