[Responsive characteristics of the cells of cortex area 18 of the adult cat after chiastomy. Postoperative development; importance of the visual experience].

Patterns of unit responses in area 18 to stimulation of the ipsilateral temporal retina were studied in adult Cats at different times after complete midsagittal section of the optic chiasm. A specific postoperative evolution could thus be followed. Immediately after section, the percentage of cells reacting to light was reduced, as compared to control preparations, as well as the average areas of the receptive fields, owing to the disappearance of large eccentric fields. A progressive recovery of the normal reactive patterns occurred between 8 and 45 days after chiasmotomy, provided that the animal was placed in normal visual conditions during its postoperative period. No such recovery could be observed after 55 days, in animals kept in complete darkness after operation. Visual experience thus seems essential to this kind of functional recovery in the adult. Another characteristic of chiasmotomised Cats also appeared to depend upon postoperative visual experience, namely the development of cells with "diffuse" responses to light.