Functional properties of the H1-neurone in the third optic Ganglion of the Blowfly,Phaenicia

Abstract

Response properties of the identified H1-neurone upon monocular stimulation were investigated by means of extracellular recordings. Comparison with optomotor torque responses under the same or similar stimulus conditions demonstrated: 1. The neurone is excited by regressive pattern motion and inhibited by progressive pattern motion. Vertical motion and stationary patterns induce only weak excitatory responses (Fig. 3, 8). 2. If the spatial wavelength (λ) of the pattern is smaller than twice the interommatidial angleΔϕ, i.e.Δϕ<σ<2Δϕ, the response properties with regard to the direction of pattern movement are reversed: regressive motion causes aninhibition and progressive motion anexcitation (Fig. 8A). This finding accords with the concept of geometrical interference between the array of receptors and the moving striped pattern causing a reversal of the direction of movement of the interference pattern by 180 deg. As in the optomotor torque response, the geometrical interference is related to the interommatidial angle. 3. The response versus pattern velocity functions possess a spatial wavelength (λ) dependent maximum as do optomotor torque responses (Fig. 8). 4. The response versus pattern velocity curves share a common peak if theλ-dependence is eliminated by plotting the response versus the contrast frequency (Fig. 9). The maximum of the dependence lies atw/λ=1.4 Hz and thus agrees well with that of the optomotor torque response at 1–3 Hz (Fig. 10). 5. The size and sensitivity profile of the receptive field is similar to that obtained by evaluation of the torque response. 6. Statistical properties of the response under steady-state conditions show that the most frequent spike interval deviates from that corresponding to the average frequency: the lower the average frequency the larger the deviation. This finding is due to the asymmetrical distribution of the spike intervals. Of the two measures, the spike frequency corresponding to the most frequently occurring spike interval gives a better fit to the optomotor torque response. The neurone is excited by regressive pattern motion and inhibited by progressive pattern motion. Vertical motion and stationary patterns induce only weak excitatory responses (Fig. 3, 8). If the spatial wavelength (λ) of the pattern is smaller than twice the interommatidial angleΔϕ, i.e.Δϕ<σ<2Δϕ, the response properties with regard to the direction of pattern movement are reversed: regressive motion causes aninhibition and progressive motion anexcitation (Fig. 8A). This finding accords with the concept of geometrical interference between the array of receptors and the moving striped pattern causing a reversal of the direction of movement of the interference pattern by 180 deg. As in the optomotor torque response, the geometrical interference is related to the interommatidial angle. The response versus pattern velocity functions possess a spatial wavelength (λ) dependent maximum as do optomotor torque responses (Fig. 8). The response versus pattern velocity curves share a common peak if theλ-dependence is eliminated by plotting the response versus the contrast frequency (Fig. 9). The maximum of the dependence lies atw/λ=1.4 Hz and thus agrees well with that of the optomotor torque response at 1–3 Hz (Fig. 10). The size and sensitivity profile of the receptive field is similar to that obtained by evaluation of the torque response. Statistical properties of the response under steady-state conditions show that the most frequent spike interval deviates from that corresponding to the average frequency: the lower the average frequency the larger the deviation. This finding is due to the asymmetrical distribution of the spike intervals. Of the two measures, the spike frequency corresponding to the most frequently occurring spike interval gives a better fit to the optomotor torque response.

DOI: 10.1007/BF00660179

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@article{Eckert2004FunctionalPO, title={Functional properties of the H1-neurone in the third optic Ganglion of the Blowfly,Phaenicia}, author={Hendrik E. Eckert}, journal={Journal of comparative physiology}, year={2004}, volume={135}, pages={29-39} }