Three-channel Lissajous' trajectory of the human short latency visual evoked potentials

Three orthogonally derived voltage-time records, when plotted simultaneously on three-dimensional voltage-voltage-voltage coordinates, produce a 3-Channel Lissajous' Trajectory (3CLT). 3CLTs of short latency visual evoked potentials (SVEP) were obtained for 8 adult humans (16 eyes) in response to monocular flash stimulation. Intersubject variability of 3CLT of SVEP was small enough to enable identification along the trajectory of comparable planar-segments of approx. 3-5 ms duration across subjects. In each planar-segment, the point at which the trajectory exhibited marked bending was noted. These points were called apices and they corresponded to maxima in the trajectory's distance from the origin (Trajectory Amplitude). Intersubject variability in apex latencies was comparable to, or smaller than, peak latency variability of single-channel records. 3CLT of SVEP consisted of 8 planar-segments in each of the latency ranges of 0-40, 40-70 and 70-100 ms. Analysis of 3CLT, combining the criteria of segment planarity, apices and trajectory amplitude peaks, enabled differentiation between components that had been considered the same in surface distribution studies. 3CLT of SVEP seemed to be influenced by the direction of propagation along the visual pathway.