Waleszczyk W J, Wang C, Burke W, Dreher B
Department of Anatomy and Histology, Institute for Biomedical Research, The University of Sydney, NSW, Australia.
Neuroscience. 1999;93(3):1063-76. doi: 10.1016/s0306-4522(99)00190-6.
We have recorded from single neurons in the retinorecipient layers of the superior colliculus of the cat. We distinguished several functionally distinct groups of collicular neurons on the basis of their velocity response profiles to photic stimuli. The first group was constituted by cells responding only to photic stimuli moving at slow-to-moderate velocities across their receptive fields (presumably receiving strong excitatory W-type input but not, or only subthreshold, Y-type input). These cells were recorded throughout the stratum griseum superficiale and stratum opticum and constituted 50% of our sample. The second group of cells exhibited excitatory responses only at moderate and fast velocities (presumably receiving excitatory Y-type but not W-type input). These cells constituted only about 7% of the sample and were located principally in the lower stratum griseum superficiale. The third group of cells was constituted by cells excited over the entire range of velocities tested (1-2000 /s) and presumably received substantial excitatory input from both W- and Y-channels. These cells constituted almost 26% of our sample and were located in the lower stratum griseum superficiale, stratum opticum and the upper part of the stratum griseum intermediale. Overall, cells receiving excitatory Y-type input, i.e. the sum of group two and group three cells, constituted about a third of the sample and their excitatory discharge fields were significantly larger than those of cells receiving only W-type input. A fourth distinct group of collicular neurons was also constituted by cells responding over a wide range of stimulus velocities. These cells were excited by slowly moving stimuli, while fast-moving photic stimuli evoked purely suppressive responses. The excitatory discharge fields of these cells (presumably, indicating the spatial extent of the W-input) were located within much larger inhibitory fields, the extent of which presumably indicates the spatial extent of the Y-input. These low-velocity-excitatory/high-velocity-suppressive cells were recorded from the stratum griseum superficiale, stratum opticum and stratum griseum intermediale and constituted about 17% of the sample. The existence of low-velocity-excitatory/high-velocity-suppressive cells in the mammalian colliculus has not been previously reported. Low-velocity-excitatory/high-velocity-suppressive cells might play an important role in activating "fixation/orientation" and "saccade" premotor neurons recorded by others in the intermediate and deep collicular layers. Overall, in the majority (57%) of collicular neurons in our sample there was no indication of a convergence of W- and Y-information channels. However, in a substantial minority of collicular cells (about 43% of the sample) there was clear evidence of such convergence and about 40% of these (low-velocity-excitatory/high-velocity-suppressive cells) appear to receive excitatory input from the W-channel and inhibitory input from the Y-channel.
我们记录了猫上丘视网膜接受层中单个神经元的活动。根据它们对光刺激的速度反应特征，我们区分出了几组功能上不同的丘神经元。第一组由仅对以慢至中等速度穿过其感受野的光刺激作出反应的细胞组成（推测这些细胞接受强兴奋性W型输入，但不接受Y型输入，或仅接受阈下Y型输入）。这些细胞在整个浅层灰质和视层均有记录，占我们样本的50%。第二组细胞仅在中等和快速速度时表现出兴奋性反应（推测接受兴奋性Y型输入，但不接受W型输入）。这些细胞仅占样本的约7%，主要位于浅层灰质的下部。第三组细胞由在测试的整个速度范围内（1 - 2000°/秒）都被兴奋的细胞组成，推测它们从W通道和Y通道都接受了大量兴奋性输入。这些细胞占我们样本的近26%，位于浅层灰质下部、视层和中间灰质上部。总体而言，接受兴奋性Y型输入的细胞，即第二组和第三组细胞的总和，约占样本的三分之一，它们的兴奋性放电野明显大于仅接受W型输入的细胞。第四组不同的丘神经元也由在很宽的刺激速度范围内作出反应的细胞组成。这些细胞被缓慢移动的刺激所兴奋，而快速移动的光刺激则引发纯粹的抑制性反应。这些细胞的兴奋性放电野（推测表明W输入的空间范围）位于大得多的抑制性野内，抑制性野的范围推测表明Y输入的空间范围。这些低速兴奋/高速抑制细胞在浅层灰质、视层和中间灰质中均有记录，占样本的约17%。哺乳动物丘中低速兴奋/高速抑制细胞的存在此前尚未见报道。低速兴奋/高速抑制细胞可能在激活其他人在丘中间层和深层记录到的“注视/定向”和“扫视”运动前神经元方面发挥重要作用。总体而言，在我们样本中的大多数（57%）丘神经元中，没有迹象表明W通道和Y通道信息存在汇聚。然而，在相当少数的丘细胞（约占样本的43%）中，有明确证据表明存在这种汇聚，并且这些细胞中约40%（低速兴奋/高速抑制细胞）似乎接受来自W通道的兴奋性输入和来自Y通道的抑制性输入。
