[Electrophysiologic research on the afferent connections of embryonic neocortex allografts inserted into the projection zones of the cortex in adult rats].

Grafts of the rat fetal neocortex (the 17th-18th day of gestation) were placed into the cavity made by aspiration in the primary visual or somatosensory cortex of adult rats. Electrophysiological studies performed 3-3.5 months later showed that approximately in 50% of animals the neurons of the transplants responded to sensory stimuli of modality specific for cortical regions replaced by the transplant. These responses were elicited from local receptive fields that in some animals revealed topographic organization. Neuronal responses of transplants were elicited by local electrical stimulation of thalamic nucleus projecting to the cortical site of grafting, as by stimulation of contralateral homotopic cortical areas. Latency and temporal patterns of neuronal responses were similar to normal ones. Thus it may be concluded that afferent inputs to the cortical transplants retrace normal cortical inputs. The possible mechanisms of re-innervation of the grafts are discussed.