Yousef T, Bonhoeffer T, Kim D S, Eysel U T, Tóth E, Kisvárday Z F
Abteilung für Neurophysiologie, Ruhr-Universität Bochum, Germany.
Eur J Neurosci. 1999 Dec;11(12):4291-308. doi: 10.1046/j.1460-9568.1999.00863.x.
The functional specificity of corticocortical connections with respect to the topography of orientation selectivity was studied by optical imaging of intrinsic signals and bulk injections of fluorescent latex beads (green and red) and biocytin into layer 4. The distributions of retrogradely labelled cells and anterogradely labelled axon terminals were histologically reconstructed from all cortical laminae, and the resulting anatomical maps compared with the optically imaged functional maps. Layer 4 injections produced extensive horizontal labelling up to 2-3 mm from the injection centres albeit without the clear patchy pattern described after layer 2/3 injections (Gilbert & Wiesel 1989, J. Neurosci., 9, 2432-2442; Kisvárday et al. 1997, Cerebral Cortex, 7, 605-618). The functional (orientation) distribution of the labelled projections was analysed according to laminar location and lateral spread. With regard to the former, no major difference in the orientation topography between supragranular- (upper tier), granular- (middle tier) and infragranular (lower tier) layers was seen. Laterally, proximal and distal projections were distinguished and further dissected into three orientation categories, iso- (+/- 30 degrees ), oblique- (+/- 30-60 degrees ) and cross-orientations (+/- 60-90 degrees ) with respect to the orientation preference at the injection sites. The majority of distal connections (retrograde and anterograde) was equally distributed across orientations (35.4% iso-, 33.7% oblique-, and 30.9% cross-orientations) that are equivalent with a preponderance to dissimilar orientations (oblique- and cross-orientations, 64.6%). In one case, distal excitatory and inhibitory connections could be morphologically distinguished. For both categories, a marked bias to dissimilar orientations was found (excitatory, 63.7%; inhibitory, 86.6%). Taken together, these results suggest that the long-range layer 4 circuitry has a different functional role from that of the iso-orientation biased (52.9%, Kisvárday et al. 1997, Cerebral Cortex, 7, 605-618) layer 2/3 circuitry, and is perhaps involved in feature difference-based mechanisms, e.g. figure ground segregation.
通过内在信号的光学成像以及向第4层大量注射荧光乳胶珠(绿色和红色)和生物胞素,研究了皮质皮质连接在方向选择性地形图方面的功能特异性。从所有皮质层对逆行标记细胞和顺行标记轴突终末的分布进行了组织学重建,并将所得的解剖图谱与光学成像的功能图谱进行了比较。第4层注射产生了广泛的水平标记,距离注射中心可达2 - 3毫米,尽管没有2/3层注射后所描述的清晰斑块状模式(吉尔伯特和维塞尔,1989年,《神经科学杂志》,9卷,2432 - 2442页;基斯瓦尔迪等人,1997年,《大脑皮层》,7卷,605 - 618页)。根据层位位置和横向扩展对标记投射的功能(方向)分布进行了分析。关于前者,在颗粒上层(上层)、颗粒层(中层)和颗粒下层(下层)之间的方向地形图上未发现主要差异。在横向方面,区分了近端和远端投射,并根据注射部位的方向偏好进一步细分为三个方向类别,即同方向(±30度)、斜向(±30 - 60度)和交叉方向(±60 - 90度)。大多数远端连接(逆行和顺行)在各个方向上均匀分布(同方向占35.4%,斜向占33.7%,交叉方向占30.9%),这等同于偏向不同方向(斜向和交叉方向,占64.6%)。在一个案例中,远端兴奋性和抑制性连接在形态上可以区分。对于这两个类别,都发现了对不同方向的明显偏向(兴奋性为63.7%;抑制性为86.6%)。综上所述,这些结果表明,第4层的长程回路与偏向同方向的2/3层回路(占52.9%,基斯瓦尔迪等人,1997年,《大脑皮层》,7卷,605 - 618页)具有不同的功能作用,并且可能参与基于特征差异的机制,例如图形-背景分离。