Kahn D M, Huffman K J, Krubitzer L
Center for Neuroscience, University of California at Davis, Davis, California 95616, USA.
J Comp Neurol. 2000 Dec 11;428(2):337-54.
We examined the internal organization and connections of the primary visual area, V1, in the South American marsupial Monodelphis domestica. Multiunit electrophysiological recording techniques were used to record from neurons at multiple sites. Receptive field location, size, progressions, and reversals were systematically examined to determine the visuotopic organization of V1 and its boundaries with adjacent visual areas. As in other mammals, a virtually complete representation of the visual hemifield was observed in V1, which was coextensive with a region of dense myelination. The vertical meridian was represented at the rostrolateral boundary of the field, the upper visual quadrant was represented caudolaterally, whereas the lower visual quadrant was represented rostromedially. Injections of fluorescent tracers into V1 revealed dense connections with cortex immediately adjacent to the rostrolateral boundary, in peristriate cortex (PS or V2). Connections were also consistently observed with a caudotemporal area (CT), entorhinal cortex (EC), and multimodal cortex (auditory/visual, A/V). These results demonstrate that M. domestica possess a highly differentiated neocortex with clear functional and architectonic cortical field boundaries, as well as discrete patterns of cortical connections. Some connections of V1 are similar to those observed in eutherian mammals, such as connections with V2 and extrastriate areas (e.g., CT), which suggests that there are general features of visual system organization that all mammals possess due to retention from a common ancestor. On the other hand, connections of V1 with EC and multimodal cortex may be a primitive feature of visual cortex that was lost in some lineages, may be a derived feature of marsupial neocortex, or may be a feature particular to mammals with small brains.
我们研究了南美有袋动物家短尾负鼠初级视觉区V1的内部组织和连接。采用多单位电生理记录技术在多个位点记录神经元活动。系统地检查感受野的位置、大小、进展和反转情况，以确定V1的视拓扑组织及其与相邻视觉区域的边界。与其他哺乳动物一样，在V1中观察到视觉半野几乎完整的表征，该区域与致密髓鞘形成区共存。垂直子午线在该区域的吻外侧边界处表征，上视觉象限在尾外侧表征，而下视觉象限在吻内侧表征。向V1注射荧光示踪剂显示，与紧邻吻外侧边界的皮质（纹周皮质，PS或V2）有密集连接。还始终观察到与颞尾区（CT）、内嗅皮质（EC）和多模态皮质（听觉/视觉，A/V）的连接。这些结果表明，家短尾负鼠拥有高度分化的新皮质，具有清晰的功能和结构皮质区边界，以及离散的皮质连接模式。V1的一些连接与在真兽类哺乳动物中观察到的连接相似，例如与V2和纹外区（如CT）的连接，这表明视觉系统组织存在一些所有哺乳动物由于共同祖先保留下来的普遍特征。另一方面，V1与EC和多模态皮质的连接可能是视觉皮质的原始特征，在某些谱系中丢失了，可能是有袋类新皮质的衍生特征，也可能是小脑哺乳动物特有的特征。
