The parvocellular evoked response (Chromatic VECPs) is significantly affected by spatial orientation?

Abstract

Abstract: : Purpose:Spatial orientation sensitivity is a well known characteristic of the human retinal cortex. Amplitude differences have been demonstrated using oblique versus orthogonal stimuli (oblique effect). The oblique effect have been poorly investigated for the parvocellular pathway. Methods:Vertical and oblique patterns – generated by a VSG 2/3 graphic card (Cambridge Research, Rochester, UK) and displayed on a color Trinitron Sony monitor– have been used to record VECPs in 10 emmetropic eyes. Colour opponent (red–green and blue–yellow stimuli with a 4 Hz reversal rate) and luminance opponent (black and white with a 16 Hz reversal rate) were used to investigate the parvo and the magnocellular pathway cortical evoked response, respectively. Amplitudes obtained by different spatial orientations were compared with the Wilcoxon rank test. Results: Luminance opponent VECPs had significantly different amplitudes when spatial orientation was changed ( z = –2,85, p = 0,005), whereas colour opponent VECPs were similar when recorded at vertical and oblique orientations ( z = –0,82, p = 0,412 for red–green stimuli; z = – 1,77, p = 0,076 for blue–yellow gratings). Conclusions:Chromatic stimuli recorded by electrophysiological means are probably generated by the 4Cb blob area which is orientation insensitive.

Keywords: color vision • electrophysiology: clinical • visual cortex