The function of auditory neurons in cricket phonotaxis

SummaryThe activity of auditory receptor cells and prothoracic auditory neurons of the cricket,Gryllus bimaculatus, was recorded intracellularly while the animal walked on a sphere or while passive movement was imposed on a foreleg.During walking the responses to simulated calling song is altered since (i) the auditory sensory cells and interneurons discharged impulses in the absence of sound stimuli (Figs. 1, 3) and (ii) the number of action potentials in response to sound is reduced in interneurons (Figs. 2, 3).These two effects occurred in different phases of the leg movement during walking and therefore masked, suppressed or did not affect the responses to auditory stimuli (Figs. 3, 4). Hence there is a time window within which the calling song can be detected during walking (Fig. 5).The extra excitation of receptors and interneurons is probably produced by vibration of the tympanum because (i) the excitation occurred at the same time as the leg placement (Fig. 4), (ii) during walking on only middle and hindlegs, no extra action potentials were observed (Fig. 6), (iii) in certain phases of passive movements receptor cells and interneurons were excited as long as the ipsilateral ear was not blocked (Figs. 8, 9).Suppression of auditory responses seems to be peripheral as well as central in origin because (i) it occurred at particular phases during active and passive leg movements in receptor cells and interneurons (Figs. 1, 4, 9), (ii) it disappeared if the ear was blocked during passive leg movements (Fig. 9) and (iii) it persisted if the animal walked only on the middle and hind legs (Fig. 6).