Effects of monocular deprivation and reverse suture on orientation maps can be explained by activity-instructed development of geniculocortical connections
Mature visual cortex shows a single, binocularly matched orientation map. This matching develops without visual experience. It persists despite early monocular deprivation that largely eliminates one eye's map, followed by reverse suture (deprivation of the previously open eye and opening of the previously deprived eye), even though the two eyes lack common visual experience in this case. These results have been interpreted to suggest that the structure of orientation maps either is innately predetermined or, if it arises through self-organization, is determined by external cues such as boundary conditions or a “scaffolding” of horizontal connections. We show, to the contrary, that these results are the expected outcomes if orientation maps develop through activity-instructed, correlation-based development of the geniculocortical connections without additional cues. A weak, binocularly correlated orientation map is known to exist before deprivation onset; we previously showed how this can arise through activity-instructed development. Now we show that this initial correlation between the two eyes' maps can persist or increase despite deprivation sufficient to cause massive loss of the deprived eye's geniculocortical synaptic strength, followed by reverse suture. Given sufficient early correlated map development, each map's fate is “dynamically committed”: the two eyes' maps will converge upon a common outcome, even if developing independently. This dynamic fate commitment is retained even after severe deprivation.(Received June 11 2001)
(Accepted August 21 2001)
Key Words: Hebb synapse; Visual cortex; Striate cortex; Simple cell; Binocular cell; Monocular deprivation; V1.
c1 Address correspondence and reprint requests to: Kenneth D. Miller, Department of Physiology, University of California, San Francisco, 513 Parnassus, San Francisco, CA 94143-0444, USA. E-mail: email@example.com