What can be inferred from multiple-task psychophysical studies about the mechanisms for temporal processing?

We used different tools from experimental psychology to obtain a broad picture of the possible neural underpinnings of temporal processing in the range of milliseconds. The temporal variability of human subjects was measured in timing tasks that differed in terms of: explicit-implicit timing, perception-production, single-multiple intervals, and auditory-visual interval markers. The results showed a dissociation between implicit and explicit timing. Inside explicit timing, we found a complex interaction in the temporal variability between tasks. These findings do not support neither a unique nor a ubiquitous mechanism for explicit timing, but support the notion of a partially distributed timing mechanism, integrated by main core structures such as the cortico-thalamic-basal ganglia circuit, and areas that are selectively engaged depending on the specific behavioral requirement of a task. A learning-generalization study of motor timing also supports this hypothesis and suggests that neurons of the timing circuit should be tuned to interval durations.