A role for extraocular afferents in post‐critical period reversal of monocular deprivation.

Publisher Website
Google Scholar
Abstract
To investigate the phenomenon of acute reversibility of cortical ocular dominance, pressure block of the retinal ganglion cells and local anesthetic block of the extraocular afferents were applied to the normal eye of 6 monocularly deprived cats. Neither pressure blinding nor retrobulbar anesthesia alone produced a significant increase in the proportion of single neurons recorded from area 17 which could be driven by the deprived eye. Following combined pressure blinding and retrobulbar blockade, 64 cells (54% of all encountered) could be stimulated through the deprived eye. Of the 64 cells driven by the deprived eye following both treatments a number showed direction (30) and orientation (13) selectivity, but the majority showed non-specific receptive field properties. In 4 separate cases, of nine where the experiment could be carried out, it was possible to observe an individual neuron shift its ocular dominance. In the presence of a retrobulbar block, the 4 neurons could be driven first by the experienced eye alone, then by the deprived eye alone, and finally by the experienced eye again, all within a few minutes of the introduction and removal of pressure blinding. These findings supported previous studies which have revealed the presence of significant numbers of potentially functional cortical inputs from the deprived eye. The new finding was that removal of tonic activity from the experienced eye, while seemingly necessary to reveal these inputs, was not sufficient. An additional role in this phenomenon is played by extraocular afferents, possibly those involved in proprioception from the eye muscles.