Neural underpinnings of temporal processing: a review of focal lesion, pharmacological, and functional imaging research.

The mechanisms by which the brain times events and stores them in memory for later use is increasingly of interest to neuroscientists. There are a variety of neurological disorders in which skilled behaviors are not coordinated and appear less than fluent, which may suggest a disorder in temporal processing. In this review, two influential models are described which suggest timing deficits may be due to impairments in a timekeeping mechanism or various nontemporal processes such as motor implementation, memory, and attention. We then review focal lesion, pharmacological, and functional imaging approaches to understanding the neural underpinnings of temporal processing. Converging findings from these approaches provide support for the role of the basal ganglia in timekeeping operations. Likewise, focal lesion and some functional imaging studies are compatible with a timekeeping role of the cerebellum, though specific regions within the cerebellum that control timing operations have not been identified. In contrast, the results from recent focal lesion research suggests the right middle-frontal and inferior-parietal cortices comprise a pathway that supports attention and working memory operations, which are crucial for timing. Functional imaging data provide some converging evidence for this proposal. Functional imaging work also indicates that a right superior-temporal inferior-frontal pathway sometimes aids timing through subvocal nonlinguistic rehearsal processes. These distributed pathways maintain timekeeping operations in working memory and store representations of temporal events, which is crucial for skilled performance.