Clemo H R, Stein B E
J Neurophysiol. 1984 May;51(5):843-58. doi: 10.1152/jn.1984.51.5.843.
Using electrophysiological techniques, the present study demonstrated that substantial direct somatosensory cortical influences on the superior colliculus (SC) originate from three areas: a) SIV, b) para-SIV (the cortex adjacent to SIV but deeper in the anterior ectosylvian sulcus (AES) and for which no topography has yet been described), and c) the rostral suprasylvian sulcus. Influences also appeared to originate from SI and SII, but these may have been indirect. Detailed examination of the AES revealed that these corticotectal projections are topographically organized, and stimulation of a given cortical locus was observed to affect only those cells in the SC whose receptive fields overlapped those of cells at the stimulation site. A similar receptive-field register was found between the suprasylvian sulcus and the SC. Within this topographic pattern, considerable convergence was evident and an individual SC cell could be influenced from a surprisingly large cortical area. This was particularly evident within the representation of the forelimb. Thus, an SC cell with a receptive field covering the forelimb and paw could receive convergent input from many cortical cells with receptive fields covering all or restricted portions of this body region. Considerable corticotectal divergence also was observed within this general topographic scheme. For example, a given corticotectal site representing the digits sent projections to many different SC cells that included the digits within their receptive fields. These data are more consistent with a block-to-block than a point-to-point corticotectal projection. Somatosensory corticotectal projections excited only those SC cells that could also be activated by peripheral somatosensory stimuli. Similarly, the caudal AES, which contains auditory cells, excited only those SC cells activated also by peripheral auditory stimuli. Yet convergent influences from both auditory and somatosensory regions of the AES were observed in the SC cells that could be activated by both auditory and somatosensory stimuli. These data indicate that the AES is a major source of excitatory input to cells of the deep laminae of the SC. Since it is these deep laminae cells that project to premotor regions of the brain stem and the spinal cord, it is reasonable to suppose that the AES has a significant impact on the output signals of the SC that initiate the orientation responses to peripheral sensory stimulation.
本研究运用电生理技术证明，体感皮层对中脑上丘（SC）的实质性直接影响源自三个区域：a）体感皮层四区（SIV）；b）SIV旁区（与SIV相邻但位于前外侧裂沟（AES）更深位置的皮层，其拓扑结构尚未描述）；c）吻侧上薛氏沟。影响似乎也源自初级体感皮层（SI）和次级体感皮层（SII），但可能是间接的。对AES的详细检查显示，这些皮层-上丘投射具有拓扑组织，观察到刺激特定皮层位点仅影响SC中那些感受野与刺激位点细胞的感受野重叠的细胞。在上薛氏沟和SC之间也发现了类似的感受野对应关系。在这种拓扑模式中，明显存在相当程度的汇聚，单个SC细胞可能受到惊人的大皮层区域的影响。这在前肢的表征中尤为明显。因此，一个感受野覆盖前肢和爪子的SC细胞可以接收许多皮层细胞的汇聚输入，这些皮层细胞的感受野覆盖该身体区域的全部或受限部分。在这个总体拓扑结构中也观察到了相当程度的皮层-上丘发散。例如，表示手指的给定皮层-上丘位点向许多不同的SC细胞发送投射，这些细胞的感受野包括手指。这些数据与块对块而非点对点的皮层-上丘投射更一致。体感皮层-上丘投射仅兴奋那些也能被外周体感刺激激活的SC细胞。同样，包含听觉细胞的尾侧AES仅兴奋那些也能被外周听觉刺激激活的SC细胞。然而，在既能被听觉刺激又能被体感刺激激活的SC细胞中，观察到了来自AES听觉和体感区域的汇聚影响。这些数据表明，AES是SC深层细胞兴奋性输入的主要来源。由于正是这些深层细胞投射到脑干和脊髓的运动前区，因此可以合理推测，AES对SC的输出信号有重大影响，这些信号启动对外周感觉刺激的定向反应。
