| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
<Results from histological study>
We examined spatial distribution of tectal efferent neurons related to prey orienting behavior in the frog Rana catesbeiana. Neurobiotin was injected as retrograde tracer into the nMLF and the anterodorsal nucleus in vitro preparations. Tangential sections were cut at 40 μm with a cryostat. Spatial autocorrelogram was computed to examine the regularity of the distribution of labeled cells. The results showed that 1)the labeled output neurons are classified into two groups (type A and B) based on their cell body size, 2)in each group, cell bodies cluster together in some sections and stand alone in others, however, all of the cell bodies show characteristic periodical distribution, 3)periodical distribution of type A neurons shows the same interval throughout the tectum, while that of type B neurons shows the region-specific intervals.
<Results from behavioral study>
We calculated the turn angle of the frog (θ1), the angle of the cricket before orientation response of the frog (θ2), the error in orientation response (θ1 minusθ2), the amount of time for orientation, and the angular velocity of orienting behavior. Angular velocity of frog's orienting turn showed the step-by-step increment occurring at 20,40,and 65 degrees. The peaks of the error in orientation were observed at the amplitudes where the step-by-step change of angular velocity occurred. When the frog comes to miss the prey object, the animal increases the turning velocity to capture the prey successfully. We also found that the frog showed an inaccurate turn with predetermined amplitude to the cricket which moves a long distance before orientation response. The amplitude showed good agreement with those where the step-by-step increment of turn velocity was observed. Therefore, for such a difficult target, they may turn into the nearest predetermined position to save energy.
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