Split chiasm developmentally induced in kittens: plasticity of interhemispheric transfer in visual cortex cells.

Visual callosal transfer during development was studied in order to reveal plasticity-related compensation for the absence of direct contralateral inputs. The optic chiasm was midsagittally sectioned in 6-8 weeks old kittens (OCK) and for comparison, in adult cats (OCA). Unit recording was made during adulthood in the border area between visual cortex areas 17 and 18, namely the callosal projection zone. The proportion of cells showing interhemispheric transfer in the OCK group, as indicated by the presence of visual input from the contralateral eye was 10.5%; in the OCA cats their proportion was 4.0%. Moreover, 2.3% of the cells showed a pure transfer of input from the contralateral eye in the OCK, although none was seen in the OCA cats. Thus, during the developmental period, a plasticity induced process, albeit limited, takes place in the enhancement of interhemispheric transfer of visual information.