Burton H, Fabri M
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Comp Neurol. 1995 May 15;355(4):508-38. doi: 10.1002/cne.903550404.
This study examined cortical connections of areas 3b and 1 in 17 macaque monkeys in reference to regional somatotopography. The fluorescent retrograde tracers Fast Blue and Diamidino Yellow and the anterograde tracer Rhodamine Dextran were injected into closely related cutaneously responsive sites in primary somatosensory cortex, e.g., adjacent digits. Supra- and infragranular layers in nearly all studied areas contained labeled pyramidal cells. Labeled infragranular cells predominated at the fringes of a distribution where cells labeled from different tracer injections in the same brain intermixed more. All topographical regions across area 1 have reciprocal connections with areas 4, 3a, 3b, 1, 2, and 5. Intrinsic connections within area 1 and between it and area 2 are greatest; those with area 3b are less. Intrinsic connections within area 3b exceed all other nearby projections from this area which reciprocally connects with areas 3a, 1 and 2. Connections appear topographically organized, including those with poorly mapped regions, like area 5. These connections link representations of neighboring skin and skip map regions that include disjoint dermatomal areas. Connections from adjacent digit representations overlap; however, double-labeled cells were not found. Distal and proximal digit zones mostly interconnect within an area. Intrinsic connections spread further in area 1 than in area 3b, thereby joining more disparate topographical zones than interareal connections, which project more homotopically. The domain over which the map in somatosensory cortical area I (SI) dynamically changes following intracortical microstimulation (Recanzone, Merzenich and Dinse, Cerebral Cortex 2:181-196, 1992) may depend on the range of intrinsic connections observed in this study. The extent of connections between cortical areas was less than expected and this challenges the hypothesis that these connections directly create receptive field enlargements.
本研究参照区域躯体定位图，对17只猕猴的3b区和1区的皮质连接进行了研究。将荧光逆行示踪剂快蓝和双脒基黄以及顺行示踪剂罗丹明葡聚糖注入初级体感皮层中密切相关的皮肤反应部位，例如相邻手指。几乎所有研究区域的颗粒上层和颗粒下层都含有标记的锥体细胞。标记的颗粒下层细胞在同一大脑中不同示踪剂注射标记的细胞混合较多的分布边缘占主导。1区内的所有地形区域与4区、3a区、3b区、1区、2区和5区都有相互连接。1区内以及它与2区之间的内在连接最强；与3b区的连接较弱。3b区内的内在连接超过了该区域与3a区、1区和2区相互连接的所有其他附近投射。连接似乎是按地形组织的，包括与映射不佳的区域（如5区）的连接。这些连接连接相邻皮肤的表征，并跳过包括不连续皮节区域的映射区域。相邻手指表征的连接重叠；然而，未发现双标记细胞。远端和近端手指区域大多在一个区域内相互连接。1区内的内在连接比3b区内传播得更远，从而连接了比区域间连接更多不同的地形区域，区域间连接的投射更具同位性。体感皮层I区（SI）的图谱在皮层内微刺激后动态变化的范围（Recanzone、Merzenich和Dinse，《大脑皮层》2:181 - 196，1992）可能取决于本研究中观察到的内在连接范围。皮质区域之间的连接程度低于预期，这对这些连接直接导致感受野扩大的假设提出了挑战。
