ACTIVITY OF CENTRAL NEURONS INVOLVED IN ELECTRORECEPTION IN SOME WEAKLY ELECTRIC FISH (GYMNOTIDAE)

Abstract

Nervous responses were obtained from fish stimulated by "short-circuiting" the electric field produced by the fish and moving conductive (Ag) and nonconductive (plastic) plates in the water near the fish, parallel to its long axis. Short-circuiting produced excitatory and inhibitory responses, de- 67 pending on the position of the short-circuiting plates. Responses to moving plates were of 2 main types. Tonic or non-adapting responses which were dependent on plate position, but not on direction of movement. Phasic responses which were either dependent on direction of movement, i.e., movements in 1 direction produced excitation, while movements in the opposite direction produced inhibition, or independent of direction of movement. Among the 1st type, the response was in some units similar for Ag and plastic, and showed no clear relation between response and plate size. In other units the response had a definite relation to the size of the plate. The edges of moving plates produced excitatory responses in many units; some units were excited only by the leading or front edges. A mechanism of neural integration (differentiation) of information from 1st order to 2nd order neurons is proposed.