Milleret C, Houzel J C, Buser P
Laboratoire de Physiologie de la Perception et de l'Action, UMR 9950, Collège de France-CNRS, Paris.
Eur J Neurosci. 1994 Feb 1;6(2):193-202. doi: 10.1111/j.1460-9568.1994.tb00261.x.
The aim of this study was to investigate the development of visual callosal transfer in the normally reared cat. Two- to nine-week-old kittens and adults (used as controls) underwent section of the optic chiasm. Three days later, the animals were placed under anesthesia and paralysed; unit activities were recorded from visual cortical areas 17 and 18 and from the white matter in one hemisphere. The units were tested for their responses to visual stimulation of each eye successively. Out of 1036 recorded neurons, 185 could be activated through the eye contralateral to the explored cortex via callosal transfer. Most of them could also be driven through the ipsilateral eye via the 'direct' geniculo-cortical pathway. For animals aged > or = 2 weeks, virtually all of these units were located at the 17/18 border zone, with a majority in the supragranular layers. When activated through the corpus callosum, they displayed receptive fields located either on the central vertical meridian of the visual field or in the hemifield ipsilateral to the explored cortex. Such extension into the ipsilateral hemifield as well as receptive field disparities of binocular units decreased with age, while spontaneous activity, strength of response, orientation selectivity and ability to respond to slits moving at middle-range velocity increased. The main conclusion is that the transient callosal projections described by anatomists, which are present until 3 months of age, do not achieve supraliminar synaptic contacts with parts of areas 17 and 18 other than the 17/18 border zone, at least from 12 days after birth. However the visual callosal transfer in young animals displays some characteristics which disappear with age.
本研究的目的是调查正常饲养的猫的视觉胼胝体传递的发育情况。对2至9周龄的小猫和成年猫（作为对照）进行视交叉切断术。三天后，将动物麻醉并使其瘫痪；从视觉皮层17区和18区以及一个半球的白质记录单位活动。依次测试这些单位对每只眼睛视觉刺激的反应。在记录的1036个神经元中，有185个可以通过胼胝体传递，由与被探索皮层对侧的眼睛激活。其中大多数也可以通过“直接”的膝状体-皮层通路由同侧眼睛驱动。对于年龄大于或等于2周的动物，几乎所有这些单位都位于17/18边界区，大多数位于颗粒上层。当通过胼胝体激活时，它们的感受野位于视野的中央垂直子午线或与被探索皮层同侧的半视野中。随着年龄的增长，双眼单位向同侧半视野的这种延伸以及感受野差异减小，而自发活动、反应强度、方向选择性和对中等速度移动狭缝的反应能力增加。主要结论是，解剖学家描述的短暂胼胝体投射在3个月龄之前存在，至少从出生后12天起，除了17/18边界区之外，它们与17区和18区的其他部分没有建立超阈下突触联系。然而，幼小动物的视觉胼胝体传递表现出一些随年龄消失的特征。
