Gould H J
J Comp Neurol. 1984 Feb 20;223(2):259-301. doi: 10.1002/cne.902230209.
The total pattern of visual callosal connections was studied in the grey squirrel by using the Fink-Heimer technique for axonal and terminal degeneration and the autoradiographic and horseradish peroxidase techniques for axonal transport. The pattern of terminations was correlated with architectonic landmarks. The results show that callosal terminations are distributed in a complex fashion within the visual cortical areas. The major terminations form a band in area 17 along its border with area 18. This band is contiguous rostrally with the callosal terminations in area L that extend caudomedially onto the medial wall of the hemisphere. Caudally the band in area 17 wraps around the ventral aspect of the occipital pole and ends medially at the level of the hippocampus. This band exhibits a distinct periodicity in the density of terminations. The callosal terminations in area 18 are usually found along the lateral and medial borders and are concentrated in discrete patches. The pattern in area 19 exhibits two or three primary patches and only loosely corresponds to the borders of the area. Few callosal terminations are found in area 19p and the posterior temporal area, Tp, while the intermediate temporal area, Ti, receives an extensive input. The laminar distribution of callosal terminations is different in each area studied. Characteristically, area 18 has dense terminations in layers III, II, and the inner one-half of layer I, with less dense terminations in layers V and VI, and sparse terminations in layer IV. Area 17 has a similar pattern in the supragranular and infragranular layers but also has dense terminations in layer IV. The patterns in area 19 are intermediate between these extremes but are more similar to those in area 17. The cells that give rise to the callosal projections were found primarily in layers III and V and occasionally in layers II, IV, and VI. The distribution of the callosal efferent neurons is more extensive than the areas of terminations. The distribution of callosal terminations suggests that the organization of visual cortical areas in the grey squirrel is more complex than had been previously recognized. This finding is discussed with reference to the general organization of the mammalian visual cortical areas, and a need for more extensive analyses of visual cortical areas in the grey squirrel, particularly with respect to extrastriate visual areas, is indicated.
通过运用用于轴突和终末变性的芬克 - 海默技术以及用于轴突运输的放射自显影和辣根过氧化物酶技术，对灰松鼠的视胼胝体连接的整体模式进行了研究。终末模式与结构标志相关联。结果表明，胼胝体终末在视皮质区域内以复杂的方式分布。主要终末在17区沿着其与18区的边界形成一条带。这条带在前方与L区的胼胝体终末相连，L区的胼胝体终末向尾内侧延伸至半球的内侧壁。在17区，这条带在尾侧围绕枕极的腹侧，在内侧止于海马水平。这条带在终末密度上呈现出明显的周期性。18区的胼胝体终末通常沿着外侧和内侧边界发现，并集中在离散的斑块中。19区的模式呈现出两到三个主要斑块，并且只是大致对应于该区域的边界。在19p区和颞后区Tp中发现的胼胝体终末很少，而颞中区Ti接受广泛的输入。在所研究的每个区域中，胼胝体终末的层状分布都不同。典型的是，18区在III层、II层和I层的内半部有密集的终末，在V层和VI层终末较稀疏，在IV层终末稀少。17区在颗粒上层和颗粒下层有类似的模式，但在IV层也有密集的终末。19区的模式介于这两个极端之间，但更类似于17区的模式。产生胼胝体投射的细胞主要在III层和V层中发现，偶尔在II层、IV层和VI层中发现。胼胝体传出神经元的分布比终末区域更广泛。胼胝体终末的分布表明，灰松鼠视皮质区域的组织比以前认识到的更为复杂。参照哺乳动物视皮质区域的一般组织对这一发现进行了讨论，并指出需要对灰松鼠的视皮质区域进行更广泛的分析，特别是关于纹外视区的分析。
