Imaging the spatiotemporal dynamics of cognition with high-resolution evoked potential methods

Subsecond temporal resolution is necessary to resolve the changes in brain activity that are associated with task-related cognitive processes. Evoked potentials (EPs) provide the requisite millisecondrange temporal resolution, and do so with nonencumbering recordings at a reasonably low cost. These features would seem to make EPs the ideal complement to structural and functiona magnetic resonance images (MRIs) and positron emission tomography (PET). However, until recently, the utility of EPs has been limited by their poor spatial resolution. Sufficient spatial correspondence has not existed between EPs and other brain imaging modalities to determine unambiguously the relationship between a sequence of EP components and structures visualized by MRI or PET. We describe progress that has been made toward overcoming this obstacle by registering electrophysiological data with anatomical information from each subject's MRI, by improving the spatial resolution of the EP, and by using analytic methods for measuring the spatiotemporal dynamics of distributed neurocognitive processes. The use of these techniques is illustrated by reviewing several experiments in which sequences of component neural processes were measured during cognitive tasks. © 1994 Wiley-Liss, Inc.