| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
The aim of this project is to elucidate the neural process of extraction and integration of directional information of air current in the cricket cercal sensory system, using calcium imaging and electrophysiological techniques. In 2004, the calcium imaging of the mechanosensory afferent neurons demonstrated that air-current stimuli from different directions induced different spatial patterns of Ca^<2+> elevation in the terminal arbors of sensory afferents within the terminal abdominal ganglion. To characterize the spatial patterns of the air-current-evoked ensemble activity of afferents, the optically-recorded responses to the repeated air-current stimuli from different directions were averaged and filtered. Based on the averaged image, we derived activity-pattern maps representing the direction of air current within the afferent projection. In 2005, we simultaneously monitored the Ca^<2+> responses to air-current stimuli at the dendrites of the identified giant interneurons (Gls) and
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the mechanosensory afferent terminals having synaptic connections on that dendritic branch. And, we compared the directional tuning properties of the postsynaptic GIs 10-2 and 10-3, which have different dendritic arborization pattern. The results suggest that the individual dendrite of 10-3 extracts distinct directional sensitivities from presynaptic afferents in the local region occupied by that dendritic branch. On the other hand, the dendrites of 10-2 extracts the directional information represented by ensemble activity patterns within the afferent projection. Since the electrotonic distances from the spike-initiating zone (SIZ) to each dendrite in 10-3 vary from each other, the directional sensitivity extracted by the nearest dendrite from SIZ will dominate the tuning properties of the voltage responses. In 10-2, the electrotonic distances from SIZ to each dendrite were close to each other. Therefore, the directional sensitivity extracted by all dendrites will be reflected to the overall tuning properties under the same weight. It is possible that the differences in the distribution of synaptic weights due to the dendritic geometry may be related to algorithm for the extraction and integration of the sensory information in the postsynaptic interneurons. Less
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