| Co-Investigator(Kenkyū-buntansha) |
SHIMIZU Toshinobu Hokkaido Univ., Res.Inst.Electron.Sci., Instructor, 電子科学研究所, 助手 (60250510)
BABA Yoshichika Hokkaido Univ., Res.Inst.Electron.Sci., Instructor, 電子科学研究所, 助手 (30238232)
MIZUNAMI Makoto Hokkaido Univ., Res.Inst.Electron.Sci., Assoc.Professor, 電子科学研究所, 助教授 (30174030)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Neuronal pathways, which operate as non-linear signal processors, were decomposed into several elements by using engineering method od informatics, and the internal mechanisms were revealed.
First, accuracy of decomposition into sandwich system, a cascade of two linear filter elements sandwiching a nonmemory nonlinear element, was evaluated. The length of time domain data necessary for the element estimation ofinsect sensory system was determined for the z-transform method of the first and second Wiener kernels. Second, details of dynamics of the pulse density encoding mechanism of the insect wind receptor were extracted after removing the statistical response properties given by Wiener kernels. The refractory period of spike initiation was the origin of the hysteresis in the pulse density incoding.Third, input pathways to cercal sensory interneurons of cricket were studied. It was found that the spiking and nonspiking interneurons have different organizations of input pathway. Fourth, a new method for sandwich system decomposition, in which Laguerre functions were used to expand Wiener kernels, was developed. Fifth, by using the single electrode current clamp recording method, signal transfer from the synaptic current to spike train sequence in the cricket cercal sensory interneuron was determined. The post-synaptic membrane was confirmed as an integrating, passive low-pass filter, while the spike initiation area was identified as a band-pass active filter. Sixth, the stochastic resonance and the effects of noise in spike encoding were studied by numerical solution of the Hodgkin-Huxley model. Noise plays an essential role for spike encoding rather than deteriorating the signal.
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