Clemo H R, Stein B E
J Neurophysiol. 1986 Jun;55(6):1352-68. doi: 10.1152/jn.1986.55.6.1352.
The corticotectal influences of somatosensory cortex were investigated by using reversible deactivation of cortex by cooling. More than half of the somatosensory superior colliculus (SC) cells studied exhibited a response depression (often not apparent qualitatively) or an elimination of responses to somatosensory stimuli during the period in which cortex was rendered inactive. Responses were restored to their initial levels by cortical rewarming. Hyperresponsiveness was never observed as a consequence of cortical cooling. Susceptibility to cooling-induced depression was not invariably linked to a specific cell type, location in the SC, or receptive-field size. Yet cells that had small receptive fields and were activated by hair displacement had the highest probability of being affected by this procedure. In some cells a contraction of the receptive field was induced by cortical cooling. This observation is consistent with previous experiments that showed that SC somatosensory receptive fields are constructed by the convergence of ascending and descending inputs and indicates that the responsiveness of specific receptive-field regions may depend on the functional integrity of cortex. Two cortical regions were found to produce cooling-induced effects in somatosensory SC cells: 1) SIV (and para-SIV), located in the anterior ectosylvian sulcus, and 2) the cortex within the rostral suprasylvian sulcus. These results indicate that somatosensory cortex, like visual cortex, plays a critical role in modulating the responses of SC cells. Apparently, the ability of both somatosensory and visual SC cells to code the presence of peripheral stimuli depends largely on the functional influences of their respective cortices. However, in contrast to previous observations on visual corticotectal influences, no specific receptive-field properties could be shown to be impressed on SC cells by somatosensory cortex.
通过冷却使皮层可逆失活，研究了体感皮层对顶盖的影响。在使皮层失活的期间，超过一半被研究的体感上丘（SC）细胞表现出反应抑制（通常在定性上不明显）或对体感刺激的反应消失。皮层复温后，反应恢复到初始水平。从未观察到由于皮层冷却而导致的反应过度。冷却诱导的抑制敏感性并非总是与特定的细胞类型、在SC中的位置或感受野大小相关联。然而，那些具有小感受野并被毛发移位激活的细胞受此操作影响的可能性最高。在一些细胞中，皮层冷却会诱导感受野收缩。这一观察结果与先前的实验一致，先前实验表明SC体感感受野是由上行和下行输入的汇聚构建而成，这表明特定感受野区域的反应性可能取决于皮层的功能完整性。发现有两个皮层区域会在体感SC细胞中产生冷却诱导的效应：1）位于外侧沟前部的IV区（和IV区旁），以及2）嘴侧上薛氏沟内的皮层。这些结果表明，体感皮层与视觉皮层一样，在调节SC细胞的反应中起关键作用。显然，体感和视觉SC细胞编码外周刺激存在的能力在很大程度上取决于它们各自皮层的功能影响。然而，与先前关于视觉皮层对顶盖影响的观察结果不同，体感皮层并未显示出给SC细胞留下特定的感受野特性。
