Pattern Evoked Potentials as Indicators of Functional Visual Field Asymmetries

It has long been known that the pattern VEP elicited by stimulation of the upper half of the visual field differs in form from that elicited by stimulation of the lower half. It has been suggested that this is due to polarity inversion of components (Michael & Halliday 1971; Jeffreys & Axford 1972; Jeffreys & Smith 1979). An alternative view is that it is due to changes in component latency (Eason, White & Oden 1967; Lehmann, Meles & Mir 1977; Lehmann & Skrandies 1979). The latter authors have also suggested that their results indicate different properties of human lower and upper hemi-retina systems.