Savaki H E, Dalezios Y
Department of Basic Sciences, School of Health Sciences, University of Crete, Iraklion, Greece.
Prog Neurobiol. 1999 Aug;58(6):473-540. doi: 10.1016/s0301-0082(98)00080-x.
The strategies used by the macaca monkey brain in controlling the performance of a reaching movement to a visual target have been studied by the quantitative autoradiographic 14C-DG method. Experiments on visually intact monkeys reaching to a visual target indicate that V1 and V2 convey visuomotor information to the cortex of the superior temporal and parietoccipital sulci which may encode the position of the moving forelimb, and to the cortex in the ventral part and lateral bank of the intraparietal sulcus which may encode the location of the visual target. The involvement of the medial bank of the intraparietal sulcus in proprioceptive guidance of movement is also suggested on the basis of the parallel metabolic effects estimated in this region and in the forelimb representations of the primary somatosensory and motor cortices. The network including the inferior postarcuate skeletomotor and prearcuate oculomotor cortical fields and the caudal periprincipal area 46 may participate in sensory-to-motor and oculomotor-to-skeletomotor transformations, in parallel with the medial and lateral intraparietal cortices. Experiments on split brain monkeys reaching to visual targets revealed that reaching is always controlled by the hemisphere contralateral to the moving forelimb whether it is visually intact or 'blind'. Two supplementary mechanisms compensate for the 'blindness' of the hemisphere controlling the moving forelimb. First, the information about the location of the target is derived from head and eye movements and is sent to the 'blind' hemisphere via inferior parietal cortical areas, while the information about the forelimb position is derived from proprioceptive mechanisms and is sent via the somatosensory and superior parietal cortices. Second, the cerebellar hemispheric extensions of vermian lobules V, VI and VIII, ipsilateral to the moving forelimb, combine visual and oculomotor information about the target position, relayed by the 'seeing' cerebral hemisphere, with sensorimotor information concerning cortical intended and peripheral actual movements of the forelimb, and then send this integrated information back to the motor cortex of the 'blind' hemisphere, thus enabling it to guide the contralateral forelimb to the target.
通过定量放射自显影14C-DG方法，对猕猴大脑在控制向视觉目标进行伸手动作的表现时所采用的策略进行了研究。对视力正常的猕猴伸手抓取视觉目标的实验表明，V1和V2将视觉运动信息传递到颞上沟和顶枕沟的皮层，这可能编码了运动前肢的位置，还传递到顶内沟腹侧部分和外侧壁的皮层，这可能编码了视觉目标的位置。根据在该区域以及初级体感皮层和运动皮层的前肢表征中估计的平行代谢效应，也表明顶内沟内侧壁参与了运动的本体感觉引导。包括弓状后下骨骼运动和弓状前动眼神经皮层区域以及尾侧主周围46区在内的网络，可能与顶内沟内侧和外侧皮层并行参与感觉-运动和动眼神经-骨骼运动转换。对裂脑猕猴伸手抓取视觉目标的实验表明，无论其视力正常还是“失明”，伸手动作总是由与运动前肢对侧的半球控制。两种补充机制弥补了控制运动前肢的半球的“失明”。首先，关于目标位置的信息来自头部和眼睛运动，并通过顶下皮层区域发送到“失明”半球，而关于前肢位置的信息来自本体感觉机制，并通过体感皮层和顶上皮层发送。其次，与运动前肢同侧的小脑蚓部小叶V、VI和VIII的半球延伸部分，将由“有视力”的大脑半球传递的关于目标位置的视觉和动眼神经信息，与关于前肢皮层预期和外周实际运动的感觉运动信息相结合，然后将这些整合信息发送回“失明”半球的运动皮层，从而使其能够引导对侧前肢指向目标。
