ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. The wind-velocity threshold of cercal interneurons of the cricketGryllus bimaculatus D. was measured using a sinusoidally alternating aircurrent stimulus. Two stimulus parameters, peak velocity and alternating frequency of the air current, were separately controlled. The measurements of the minimum velocity evoking a response at a variety of frequencies gave a threshold curve. The stimulating apparatus was a wind tunnel which consisted of a pair of push-pull driven loudspeakers. The peak velocity was controlled within the range of 300 mm/s-0.01 mm/s (90 dB) and the frequency between 2 Hz and 100 Hz. 2. The interneurons were classified in three types: P- (phasic), T- (tonic), PT- (phasic-tonic) in accordance with their adaptation rate to a ‘burst stimulus’ of alternating air current (Fig. 3). The threshold curve of each type of interneuron showed distinctive dependency on the frequency. Seven cercal interneurons were characterized by their differing threshold curves, and six of them were morphologically identified using Lucifer Yellow marking after intracellular recording. 3. The velocity threshold of the two P-type interneurons decreased by about 20 dB for a decade increase of alternating frequency; it seems, therefore, that they work as acceleration detectors. Their thresholds were about 0.06 m/s2 and 1.1m/ s2, respectively. The one with the lower threshold was identified as 9-1 (LGI: the lateral giant interneuron) (Fig. 4). 4. T-type interneurons showed high sensitivity to a lower frequency of air current. Their threshold curves were almost flat (Fig. 5). They are velocity dependent and their threshold values are about 30 μm/s at 5 Hz. The two T-type interneurons respond to the in- and anti-phases of the alternating air current (Fig. 6 A); their preferred directions are opposite to each other. They were morphologically identified as the sensory interneurons 10-2 and 10-3. 5. Three PT-type interneurons 8-1 (MGI: medial giant interneuron), 9-2 and 9-3 were also identified. MGI had threshold curves with slopes of 30 dB per decade change of frequency (dB/dec) while the other two had 20 dB/dec slopes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00605235
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