Cognitive neuroscience of interval timing

Precise representations of magnitude estimations (e.g., size, weight, intensity, duration) are crucial for the ability to accurately perceive and act in the world. Whereas the neural basic for many magnitude dimensions are well understood, very little is known about how the brain represents brief intervals of time ranging from milliseconds to tens of seconds. In a series of experiments we test the hypothesis that distributed neural networks mediate the functioning of an accumulating clock stage and a comparator stage of an internal clock. In experiment 1, subjects performed a temporal discrimination task during fMRI acquisition that allowed us to isolate discrete neural activity evoked by different components of a putative internal clock model. Left cortical regions including inferior frontal cortex, supplemental motor area and superior temporal gyrus support accumulator functioning whereas bilateral inferior frontal gyri supports comparator functioning. In experiments 2 and 3 we correlated temporal vulnerabilities with lesion locations in patients with brain injuries. Lesion analyses implicated similar structures involved in the accumulating clock stage as those found in experiment 1. Furthermore, in experiment 2, patients showed double dissociations between performances on a temporal order judgment and size judgment tasks and voxel lesion symptom mapping (VLSM) revealed partially independent neural networks. Taken together these data provide evidence for interactions between size and time processing; however, they do not provide evidence for a unified magnitude estimation system. In Experiment 3 we use power function analyses to describe impairments of temporal judgments in patients with focal brain lesions. VLSM revealed that damage to posterior superior temporal gyrus appears to disrupt the pulse width while damage to the posterior temporal and inferior parietal cortex appears to dysregulate the accumulator in interval timing.