1999 Fiscal Year Final Research Report Summary
Origin of the Internal Noise in Insect Mechanoreceptor and Role of the Noise for Weak Signal Detection
| Project/Area Number |
10640658
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
動物生理・代謝
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
SHIMOZAWA Tateo Hokkaido University, Research Institute of Electronic Science, Professor, 電子科学研究所, 教授 (10091464)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Mechanoireceptor / Cricket / Wind Receptor Hair / Sensory Threshold / Energy Threshold / Thermal Noise / Weak Signal Detection / Fluctuation Analysis |
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| Research Abstract |
Minimum amount of mechanical energy necessary to cause a neuronal spike in the wind receptor cell of cricket is determined to be at the order of kT (4×10ィイD1-21ィエD1 J at 300°K). The insect mechanoreceptors are therefore facing to the thermal noise of Brownian motion, when working near threshold. The evolution however has achieved a paradoxical solution for sensory signal transmission under the noise problem. Here we show the determination of mechanical energy and the information theoretic analysis on sensory spike trains of the insect mechanoreceptor.
The estimation of the mechanical energy is based on three measurements, deflection sensitivity, sensory threshold, and mechanical resistance of hair support. The deflection sensitivity to air motion was measured by laser-Doppler velocimetry and Gaussian white noise analysis. The mechanical parameters, I.e. the moment of inertia of hair shaft, the spring stiffness of hair support, and the torsional resistance within the support were estimated by applying Stokes' theory for viscous force. Mechanical energy consumed by the resistance provides the maximum estimates of energy available to the receptor cell for stimulus transduction. The energy threshold of the mechanoreceptor is far below that of single photon quantum of visible light (ca. 3×10ィイD1-19ィエD1 J). The mechano-receptor is 100 times more sensitive than photoreceptors.
Spike train of the wind receptor cell fluctuates in timing, when responding to weak stimuli near threshold. Simultaneous double recording from two cells revealed that the fluctuations are non-correlated between cells. The receptor array has utilized the cell-intrinsic noise for stochastic sampling of weak sub-threshold signals, and paradoxically improved the detection of signals under the inevitable thermal noise.
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