Centrifugal optic nerve responses evoked by auditory and somatic stimulation

Abstract

The evidence for the efferent control of receptor events has recently been repeatedly challenged. The present experiments were undertaken to provide a simple demonstration of the existence of such a mechanism. Clicks were presented to unanesthetized cats and bipolar recordings made of potential changes evoked in the optic nerve and tract with implants of small (300 μ spaced about 0.2 mm) electrode wires. Click initiated optic nerve responses of 10–60 μv amplitude were obtained in fourteen cats at a latency of 20 msec. These responses were unaffected by atropinization or by curarization; they showed amplitude decrement upon repeated presentations and were unobtainable when the animal was restless. They were abolished by bilateral section of the optic tracts central to the implant sites. Similar optic nerve responses could be initiated by tactile stimulation. Also, silent flash produced recordable responses in the eighth cranial nerve. Finally, parametric click-flash interaction effects were observed to differentially affect different fibers in the optic nerve and to alter the B wave of the ERG.