Lambda waves evoked by retinal stimulation in the absence of eye movements

Abstract

The present experiment verified the hypothesis that lambda waves are evoked potentials in response to visual image movement, and are not necessarily associated with eye movement. Retinal stimulation comparable to saccadic eye movement was produced by 200 msec periods of movement of vertical black and white stripes before the immobilized eyes of cats. Potentials identical to the previously described feline lambda waves were elicited by the onset and sometimes termination of stripe movement. They were recorded from chronically implanted macroelectrodes not only at the visual cortex, but also at the optic tract and lateral geniculate nucleus. The amplitude and latency of these potentials varied systematically with stripe width and velocity, but most closely with the frequency of black-white contrast alternation over the retina. Cellular mechanisms for these phenomena were proposed, and the differences between the lambda wave and other eye movement related potentials (PGO wave, EMMD, calcarine cortex potential, corollary discharge and efference copy) were discussed. It was concluded that the lambda wave may be related to that part of perceptual and particularly evoked potential depression which follows the onset of eye movement in a non-homogeneous environment.