Introduction

The chapters in this book have described current ideas about the functional and neural mechanisms involved in timing behaviors and the temporal judgments of intervals. We optimistically conclude that current and future imaging techniques will soon allow a detailed understanding of the neural circuits involved in interval timing. We can, however, envisage two pitfalls that might slow progress if not treated with caution. The first is the probability that multiple mechanisms are involved in time measurement, and that these are functionally and anatomically discrete. If unrecognized, such duplicity of mechanisms could lead to extreme confusion regarding the locus and function of neural timing systems. The second pitfall is associated with the inherent limitations of neuroimaging techniques and the implications of these for investigations of time measurement. We believe that due to the sluggish and indirect nature of some techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), and the spatial imprecision of others, such as electroencephalography (EEG) and magnetoencephalography (MEG), neuroimaging results must be interpreted with great caution when used to investigate a delicate system such as that used for time measurement.

We will address these pitfalls by raising two general questions: First, does all human interval timing depend on the same basic neural system, or are fundamentally different processes used in different timing tasks? Second, to what extent can we expect functional imaging techniques to be useful in describing the detailed function of the mechanisms involved?

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