Noninvasive Functional Investigations into Human Cortical Motor Physiology, Motor Learning, and Motor Imagery

Abstract

In humans, registration of regional cerebral blood flow (rCBF) and electrophysiological recordings offer the possibility to (a) study directly parameters of brain activity and (b) establish functional-anatomical relations in behavioral tasks. Current trends in imaging of brain functions include the use of scalp-recorded negative DC potential shifts which are time-locked to the performance of cognitive or motor tasks. A reason for utilizing this phenomenon is the notion of the physiological significance of DC potential shifts as recordable from the scalp surface; it has clearly been established that excitatory synaptic currents of cortical neurons generate electrical dipoles that are negative on the surface and positive at depth. The spatial resolution of scalp-recorded DC potential shifts is limited but is, for example, sufficient for separating neuronal activity of circumscribed cortical areas involved in the execution of movements of different parts of the body (Boschert and Deecke 1986). Spatial transformations of EEG recordings (e.g., Laplacian) can offer additional possibilities for estimating current sources contributing to surface-recorded electrical shifts and may help to distinguish different sources underlying these shifts.