Formulating representations of time: an event-related fMRI study

We studied the neural underpinnings of temporal cognition by distinguishing brain activation related to encoding time intervals from activation associated with discriminating intervals. The relationship between brain activity and behavioral measures of timing difficulty was also investigated to elucidate the functional role of neural systems mediating temporal discriminations. Healthy adults underwent fMRI as they made judgments about whether a comparison tone-pair was longer or shorter than a standard tone-pair (1200 or 1800 ms). The main results showed activation in the bilateral caudate, right inferior parietal cortex, left middle frontal cortex (BA 6), and left hippocampus during interval encoding. Interval comparison was associated with activation in bilateral middle frontal cortex (BA 9,10,46), parahippocampus, and cerebellum. Harder interval discriminations produced greater activation in the prefrontal and inferior parietal cortices; easier discriminations produced greater activation in bilateral parahippocampus. The results implicated the striatum and right inferior parietal cortex in clock processes and the medial temporal lobes in encoding and retrieval of interval representations.