Binocular phasic coactivation does not prevent ocular dominance segregation

Abstract

The segregation of geniculo-cortical afferents into ocular dominance columns is an activity-dependent process. It was hypothetized that this process is susceptible to the temporal patterning of the retinal input. Accordingly, asynchronous activation of the two eyes should enhance ocular dominance segregation but synchronous activation should decrease or prevent it. In order to test the second part of the hypothesis, kitten were raised in strobe light which phasically coactivated the retinal inputs during 10 microsecond flashes at 8Hz. Strobe rearing prevents retinal motion signals but allows vision of stationary contours. At the age of 10-14 weeks, ocular dominance columns were labeled either transneuronally by [3H]-proline or by [ I4C]-2-deoxyglucose autoradiography. Contrary to the hypothesis, ocular dominance columns were very well segregated and the pattern closely resembled the pattern observed in squinting cats. We conlude that the light flashes were sufficient to enable binocular competition and that ocular dominance segregation was supported by the mismatch of the stationary contours. Our result thus emphasizes a feature-selective mechanism over mere global temporal patterning of retinal signals.