Kretz R, Rager G, Norton T T
J Comp Neurol. 1986 Sep 1;251(1):135-45. doi: 10.1002/cne.902510110.
The organization of ON and OFF responses and ocular dominance in the striate cortex of the tree shrew was electrophysiologically investigated by using flashed, stationary visual stimuli presented monocularly to either the ipsilateral or contralateral eye. We measured cortical multi-unit activity at 25-micron intervals with glass-insulated platinum-plated tungsten microelectrodes. Penetrations were made perpendicular to the cortical layers and the responses were quantitatively analyzed in layers IIIc to V. In sublayers IIIb, IIIc, and upper V, phasic responses of approximately equal magnitude occurred to both light ON and light OFF (ON-OFF regions). In layer IV, tonic as well as phasic responses were often evoked by the flashed spot of light. In sublayer IVa stronger responses occurred to light ON than to light OFF (ON region) while in sublayer IVb stronger responses occurred to light OFF than to light ON (OFF region). In an ON region, the increased neural activity that occurred at light ON was often accompanied by a decrease in activity below baseline level at light OFF. A similar decrease often occurred in an OFF region at light ON. Recordings from the region of the cell-sparse cleft in layer IV were characterized by ON-OFF responses, signalling a transition zone between sublayers IVa and IVb. In addition, the responses to stimulation of the ipsilateral eye typically were very weak in the cleft region. In the other regions examined, the multi-unit activity generally was driven binocularly with slightly greater responses being elicited by the contralateral eye. We conclude that the ON-center and OFF-center afferent pathways that are organized at the retinal level remain generally segregated in the tree shrew through the first synapse in the striate cortex. In addition, our recordings confirm that a horizontal organization of ocular dominance occurs in layer IV of the striate cortex in tree shrews.
通过向树鼩同侧或对侧眼单眼呈现闪烁的静止视觉刺激，用电生理学方法研究了树鼩纹状皮层中开反应和关反应的组织以及眼优势。我们使用玻璃绝缘镀铂钨微电极以25微米的间隔测量皮层多单位活动。电极垂直于皮层各层插入，并对IIIc至V层的反应进行定量分析。在IIIb、IIIc和V层上部，光开和光关时出现幅度大致相等的相位反应（开-关区域）。在IV层，闪光光斑经常诱发紧张性和相位反应。在IVa亚层，光开时的反应比光关时更强（开区域），而在IVb亚层，光关时的反应比光开时更强（关区域）。在开区域，光开时神经活动的增加通常伴随着光关时活动降至基线水平以下。在关区域，光开时也经常出现类似的下降。IV层细胞稀疏裂隙区域的记录特征为开-关反应，表明IVa和IVb亚层之间的过渡区。此外，在裂隙区域，对同侧眼刺激的反应通常非常弱。在检查的其他区域，多单位活动通常由双眼驱动，对侧眼引起的反应略强。我们得出结论，在视网膜水平组织的开中心和关中心传入通路在树鼩中通过纹状皮层中的第一个突触大体上保持分离。此外，我们的记录证实树鼩纹状皮层IV层存在水平方向的眼优势组织。
