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

lsthmi核只接受同侧视神经顶盖的输入，并投射回同侧和对侧视神经顶盖。本研究旨在阐明峡顶投影的功能重要性。电刺激地峡核，记录上侧和对侧视顶盖的场电位。采用电流源密度分析方法，计算了汇流槽的场电位和深度分布，并计算了汇流槽的电流源密度。得到了以下结果：对侧峡顶投影有两个短潜伏期的sink。第8层的一组纤维与第6层的神经元单突触接触。表层的另一纤维群与第8层的神经元单突触接触。长潜伏期的第三汇的存在表明第6层神经元接受来自地峡核的多突触输入。同侧峡顶投影6层的神经元接收到8层的单突触输入。另一个延迟较长的sink表明第6层向第9层投射树突的神经元接受多突触输入。

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.