POST EYE-OPENING MATURATION OF VISUAL RECEPTIVE-FIELD DIAMETERS IN THE SUPERIOR COLLICULUS OF NORMAL-REARED AND DARK-REARED RATS

When the rat's eyes open (P14) the retino-collicular projection is lar gely mature but the cortico-collicular afferents are naive and mature considerably in the following week. At P14, single units in the superi or colliculus' superficial grey layer (SGS) had discrete receptive fie lds (RFs) (diameter = 15 +/- 1.6 degrees) which expanded with age, rea ching 30 +/- 2.6 degrees at P21, possibly reflecting the increasing in fluence of the visual cortex, whose RFs are known to be enlarged at P2 1. Subsequently SGS RFs retracted to 13 +/- 1.30 by P23. Dark-reared ( DR) rats followed a similar but delayed developmental pattern, such th at RFs were still large (27 +/- 3.4 degrees) at P24. By P30 however th e RFs of DR rats were the same as those of normal adults. Thus visual experience accelerates the emergence of normal RFs in the SGS. (C) 199 7 Elsevier Science B.V.