Source Geometry And Dynamics Of The VEP

Source Geometry and Dynamics of the Visual Evoked Potential

Howard A.Gutowitz, Vance Zemon, Jonathan D. Victor and Bruce W. Knight

Electroencephalography and Clinical Neurophysiology, 64: 308-327 (1986)

Summary

A method is developed for the analysis of the steady-state visual evoked potential (VEP) recorded at an array of electrodes. The VEP is assumed to result from the sum of a number of independent mechanisms. Each mechanism proves to have a fixed intracerebral source (independent of stimulus paradigm) and dynamics which depend on the stimulus. The steps in the analysis are: (1) Fourier analysis of the responses and retention of the first 4 even harmonics; (2) factor analysis in the frequency domain; (3) an invariant representation ('the invariant fingerprint') of the geometric information contained in the factor analysis; and (4) interpretation of the invariant fingerprint in terms of a simple biophysical model. This analysis is applied to responses elicited by a contrast-reversing checkerboard. The dependence of the midline VEP wave form on reversal frequency, check size, and area of stimulation (upper, lower, and full-field) reflects a change in the dynamics of the generators, rather than a change in their geometry.