Functional Importance of Mutual Isthmo-Tectal Projection in Visually Guided Behavior in the Frog

腹外侧核只接受同侧视顶盖的传入，并向同侧和对侧视顶盖投射。为探讨峡-顶盖投射的功能意义，电刺激峡核，记录同侧和对侧视顶盖的场电位。采用电流源密度分析法计算了汇和源的场电位和深度分布。结果表明：侧外侧峡-顶盖投射有两个潜伏期短的汇点。第8层的一组纤维与第6层神经元单突触接触。触觉浅层的另一组纤维与第8层神经元形成单突触接触。第三个潜伏期长的汇点的存在表明第6层神经元接受来自峡核的多突触输入。同侧峡-顶盖投射潜伏期短的汇点表明第6层神经元接受来自第8层的单突触输入。另一个具有长潜伏期的汇点指示将树突投射到第9层的第6层中的神经元接收多突触输入。

Nucleus lsthmi receives only input from ipsilateral optic tectum, and it project back to ipsilateral and contralateral optic tectum. This research was carried out to elucidate the functional importance of isthmo-tectal projection.Nucleus Isthmi was electrically stimulated and recorded field potentials from ipsi-and contralateral optict tectum. Current source density analysis was applied to the field potential and depth profiles of the sink and the source were calculated. The following results were obtained.Contralateral Isthmo-tectal ProjectionThere are two sinks with short latency. One fiber group at layer 8 contact monosynaptically to the layer 6 neurons. The other fiber group at superficial tactal layer make monosynaptic contacts to the neurons in layer 8. Existence of the third sink with long latency suggests that neurons in layer 6 receives polysynaptic input from Nucleus Isthmi.Ipsilateral Isthmo-tectal ProjectionThe sink with short latency indicates that neurons in layer 6 receives monosynaptic inputs in layer 8. The other sink with long latency indicates that neurons in layer 6 which projects dendrite to layer 9 receives polysynaptic inputs.