Organization of Receptive Fields of Cricket Giant Interneurons Revealed by Cercal Ablations

Abstract

ABSTRACT-In order to determine the contribution of each cercus and its receptors in organizing the receptive field of four air-motion sensitive giant interneurons (GIs 8-1, 9-1, 9-2 and 9-3 ) of the cricket Gryllus bimaculatus, effects of removing the ipsilateral or contralateral cercus (referred to the side of the axons) on specific parameters of the wind-evoked responses of these neurons were investigated. All 4 GIs received only excitatory inputs from a group of filiform hairs on the ipsilateral cercus. In addition to the ipsilateral excitatory inputs, GIs 8-1 and 9-1 received weak excitatory and strong inhibitory inputs from a group of filiform hairs on the contralateral cercus. GI 9-2 received only inhibitory inputs from filiform hairs on the contralateral cercus. GI 9-3 received excitatory inputs from filiform hairs on the contralateral cercus and no inhibitory input was confirmed. In addition to such simple excitatory and inhibitory connections, the rebound motion of cercal filiform hairs had some role in organizing the receptive fields of GIs 9-2 and 9-3. Furthermore, the possibility of using a rebound depolarization of the membrane potential for mediating the long latency response in GIs 8-1 and 9-2 will be discussed.

Functional Recovery of Cricket Giant Interneurons after Cercal Ablations

“…As most response magnitudes of GI 8-1 in 1-day ICI animals showed an increase compared to those in BCI animals ( Fig. 2; Matsuura and Kanou, 1998), the response magnitudes in 21-day ICI animals were more similar to those in BCI animals than in 1-day ICI animals (except R60 and R90). Although most of the changes which occurred during the first 20 days seemed compensational, only the changes occurred to the air currents applied from R30, L150 and L90 directions were statistically significant (P < 0.05).…”

“…The results were compared to those measured in 1-day animals (Matsuura and Kanou, 1998; companion paper) in order to explore how the response properties changed during the first 20 days.…”

“…At each stimulus direction, 10 successive air current stimuli with a particular peak velocity were applied to an insect in 5 second intervals. Details of stimulating procedures were the same as in the companion paper (Matsuura and Kanou, 1998).…”

“…After physiological investigations, the GIs were intracellulary marked with fluorescent dye Lucifer Yellow CH for a morphological identification. Details of the neural recording and intracellular marking procedures were the same as those in our companion paper (Matsuura and Kanou, 1998).…”

“…Velocity thresholds, response magnitudes and response latencies of each GI to an air current stimulus were measured 21 days after unilateral cercal ablation. The results were then compared to those measured 1 day after the same treatment (Matsuura and Kanou, 1998 and present study) in order to investigate whether a significant recovery (compensation) occurred during the first 20 days or not. Changes in the response properties of GIs, if any, must tell us a part of neural mechanisms underlying the basis of the behavioral compensation.…”