Interaction of electrosensory and electromotor signals in lateral line lobe of a mormyrid fish.

A signal associated with the neural command to discharge the electric organ is recorded in cells of the lateral line lobe. Responses of cells activated by medium receptor inputs are facilitated or less frequently inhibited during this command-associated signal. Only responses to disynaptic inputs are affected, the monosynaptic response is not altered. The periods of facilitation and inhibition occur at times at which electroreceptor activity evoked by organ discharge reaches the lateral line lobe. Presumably the command-associated signal is important in electrolocation. Cells responding to large receptor inputs are inhibited by the command-associated signal. Activity evoked by large receptors is transmitted in a mesencephalic fiber tract. The tract response is also inhibited by the command-associated signal. Since each organ discharge would excite all the large receptors at short latency, there would be little information contained in their responses. Inhibiting discharge-evoked activity may allow the system to return to maximum sensitivity most rapidly.