The effect of single giant interneuron lesions on wind‐evoked motor responses in the cockroach, Periplaneta americana

Abstract

In order to determine the contribution of individual giant interneurons (GIs) to wind-evoked motor outputs, responses were recorded from depressor and levator motor neurons in the cockroach Periplaneta americana to wind puffs of different directions. The depressor response was generally stronger to wind from the ipsilateral rear than to wind from the contralateral rear. The levator response was more variable but was more often stronger to wind from the contralateral rear than to wind from the ipsilateral rear. These results are as expected based on behavioral responses to wind puffs. (Camhi and Tom, 1978). The depressor response was nearly or totally abolished by severing the ipsilateral connective of the nerve cord but was little affected by severing the contralateral connective. The levator response was greatly reduced for some angles by severing the ipsilateral connective and for other angles by severing the contralateral connective. Blocking conduction in the ipsilateral GI 5 nearly or completely abolished the depressor response to wind from the ipsilateral rear. This is the first time that a GI has been shown to be necessary, not just sufficient, for a given motor output.

Cartesian representation of stimulus direction: Parallel processing by two sets of giant interneurons in the cockroach

“…For instance, intracellular stimulation of a single dGI or a dGI pair consistently results in the activation of several motor-neurons innervating leg muscles (Ritzmann and Camhi 1978;Ritzmann 1981). Moreover, blocking the response of a GI 5 decreased or eliminated the wind-evoked response of a leg motor neuron (Westin and Ritzmann 1982). It has been suggested that the vGIs, which are the first to respond to wind, both control the initial part of the turn and inhibit the effects of dGI activation at the thoacic level; then, at later stages, the dGIs are disinhibited and may take control of subsequent running (Camhi 1985).…”

Response dynamics and directional properties of nonspiking local interneurons in the cockroach cercal system

“…Seven pairs of GIs have been suggested to elicit this directional escape rerectional, whereas GI 3 responds to wind from the front (Westin sponse: electrical stimulation of individual GIs elicits excitation et al, 1977). Therefore, Camhi and Levy (1989) proposed a of leg motor neurons associated with escape (Ritzmann and model of the assembly code for direction that accounts for this Camhi, 1978;Ritzmann, 1981;Ritzmann and Pollack, 1981), discrepancy, in which the number of action potentials is comand killing of the GIs can alter wind-evoked motor responses pared between the left versus the right group of ventral GIs (GIs (Westin and Ritzmann, 1982). Of these, the ventral four GIs l-4).…”