Filter characteristics of cercal afferents in the cockroach

Abstract

The response dynamics of cercal afferents in the cockroach. Periplaneta americana, were determined by means of a cross-correlation technique using a Gaussian white noise modulation of wind as a stimulus. The white noise stimulus could evoke sustained firing activity in most of the afferents examined (Fig. 1). The spike discharges were unitized and then cross-correlated with the stimulus to compute 1st- and 2nd-order Weiner kernels. The 1st-order kernels from a total of 28 afferents were biphasic and closely matched the time differential of a pulse (Figs. 1, 3 and 4). The amplitude and waveform of the kernels depended on the stimulus angle in such a way that the kernels were the mirror image of those on the polar opposite side (Figs. 2 and 3). The 2nd-order kernels were also differential. They had 2 diagonal peaks and 2 off-diagonal valleys in a 2-dimensional plot with 2 time axes (Figs. 1, 5 and 6). This 4-eye configuration was basically invariant irrespective of the stimulus angle, although the kernels varied in amplitude when the stimulus angle was changed. The time between the peak and a following trough of the 1st-order kernel was constant and had a mean of 4.6 +/- 0.1 ms, whereas the time between 2 diagonal peaks of the 2nd-order kernels was 4.7 +/- 0.1 ms (Figs. 4 and 6), suggesting that wind receptors (filiform sensilla) on cerci act as a band-pass filter with a peak frequency of about 106 Hz. The peak time, however, varies from 2.3 to 6.9 ms in both kernels, which may reflect the spatial distribution of the corresponding hairs on the cercus. The summation of the 1st- (linear) and 2nd-order (nonlinear) models precisely predicted the timing of the spike firing (Fig. 8). Thus, these 2 lower-order kernels can totally characterize the response dynamics of the wind receptors. The nonlinear response explains the directional sensitivity of the sensory neurons, while the differentiating 1st-order kernel explains the velocity sensitivity of the neurons. The nonlinearity is a signal compression in which one of the diagonal peaks of the 2nd-order kernel always offsets the downward phase of the 1st-order kernel (Fig. 7) and obviously represents a half-wave rectification property of the wind receptors that are excited by hair movement in only one direction and inhibited by hair movement in the polar opposite direction.

Processing of mechanosensory information from gustatory receptors on a hind leg of the locust

“…This means that the most effective stimulus to all the exteroceptors will be one that moves along the leg towards the body. This organisation contrasts with that of the wind sensitive hairs on the cerci of crickets and cockroaches which have directional sensitivities that vary depending on their positions on the cercus (Kondoh et al 1991;Palka et al 1977;Westin 1979).…”

“…The drawing shows the position of the basiconic sensilla on the dorsal tibia and tarsus Second, they encode the velocity of a stimulus in the frequency of their spikes. In this respect therefore they act like the surrounding tactile hairs (Newland 1991a), the tactile hairs on the cerci of cockroaches (Bufio et al 1981) and the wind-sensitive hairs on the cerci of both the cricket (Shimozawa and Kanou 1984) and cockroach (Kondoh et al 1991). Like the surrounding low angular threshold hairs they have low velocity sensitivities (l~ but are more sensitive than the high angular threshold hairs which have a threshold of 30~ (Newland 1991a).…”

Animal escapology II: escape trajectory case studies

“…Camhi and Tom, 1978;Comer and Dowd, 1987;Rinberg and Davidowitz, 2000;Stierle et al, 1994;Westin, 1979). Hairs on their abdominal cerci detect the direction of wind produced by an approaching real or simulated threat (Camhi and Tom, 1978;Kondoh et al, 1991;Thompson et al, 1992;Westin, 1979). The directional sensory wind information from these hairs is transmitted to giant interneurons (GIs) in the terminal ganglion (Kolton and Camhi, 1995).…”

Synchronous firing by specific pairs of cercal giant interneurons in crickets encodes wind direction

“…However, if the spike triggered average (STA) of the interneuron has an unidirectional waveform, i.e., the values of the waveform are mainly positive or negative, directions can be determined from that information (Kondoh et al, 1991). Applied to our experimental set-up, when the STA waveforms of the neuron showed a positive value, the neuron was assumed to respond to a wind stimulus moving from the front to the rear of the cricket.…”