A conceptual overview and critique of functional neuroimaging techniques in humans: I. MRI/FMRI and PET.

A critical evaluation of current, noninvasive brain-mapping techniques indicates that no one technique in isolation can adequately address the varied questions of interest to basic researchers and clinicians. Consequently, an integrated analysis of anatomical and functional measurements has become the ultimate goal to better characterize the nature of neuronal and hemodynamic responses to sensory and cognitive stimulation. Such an analysis will optimize both spatial and temporal resolution, thereby enabling patterns of activation to be followed throughout the central nervous system, a prerequisite for examining stages of information processing. This review, written in two parts, provides a conceptual overview of three techniques (MRI/fMRI, PET, and MEG/EEG) and examines current efforts at integrating these measures. Each technique is initially evaluated in isolation by considering a set of primary issues (e.g., spatial resolution, temporal resolution, the nature of the signal, individual variability, repeatability, etc.). The first part compares and contrasts MRI/fMRI techniques with PET. Part II, which examines MEG/EEG techniques and current attempts at integrating techniques, will appear in a subsequent volume. This two-part review focuses on issues, not results per se, and it is assumed that the reader is not proficient in any of the techniques described.