Functional compensation in lateral suprasylvian visual area following neonatal visual cortex removal in cats

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Abstract
Seven kittens received unilateral visual cortex lesions (areas 17, 18, and 19) within 30 h of birth. Single-cell recording was carried out in the lateral suprasylvian (LS) visual area of cortex when the animals were 6-8.5 mo. old. The results were compared with those from cats that received similar lesions as adults and with those from normal adult cats. In normal adult cats, 88% of the LS area neurons respond best to moving stimuli, 80% are direction selective, and over 70% are driven by both the contralateral and ipsilateral eyes. Following unilateral removal of visual cortex in adult cats, there is a decrease in the proportion of LS area cells that respond best to moving stimuli (51%), a decrease in the proportion of direction-selective cells (18%) and a decrease in the proportion of cells that respond to the ipsilateral eye (41%). Similar results were found following short (0.5-1 mo.) and long (6.5-8 mo.) survival times. Following neonatal visual cortex lesions, LS area neurons developed normal response properties: 83% of the cells responded best to moving stimuli, 74% were direction selective, and over 70% responded to the ipsilateral eye. Among the direction-selective cells, the directional tuning was normal. Other response properties of the cells also were normal. There was no evidence that a significant number of LS area cells became orientation selective or took on any of the response properties of the damaged visual cortex. Detailed histological analysis verified that the inputs from areas 17 and 18 or areas 17, 18 and 19 were removed for all LS area cells that were studied in cats with neonatal lesions. The lesions were comparable to those in cats that had visual cortex removed as adults. The results indicate that a functional compensation occurred within the remaining visual pathways and LS area following neonatal removal of visual cortex inputs. The LS area neurons developed normal receptive-field properties in spite of the absence of visual cortex. This finding correlates well with previous reports of anatomical compensation within the retinothalamic-LS cortex pathway following neonatal visual cortex lesions and with the improved behavioral recovery that occurs in cats with neontal visual cortex lesions.