Spatial sensitization and desensitization with small adapting fields: interactions of signals from different classes...

Thresholds for brief, tiny flashes were measured on small adapting fields at 5 degrees retinal eccentricity. Rod influences was eliminated by bleaching. Green and red small adapting fields raised the threshold for a green test flash by stimulating both middle and long wave cones-thus spatial desensitization by small adapting fields is not con-specific. However, a small adapting field that strongly stimulated only short wave cones did not affect the visibility of a long wave flash. Spatial sensitization was also measured, using green or red annuli that surrounded a small red field and green test probe. Sensitization was not cone-specific. Possible mechanisms producing desensitization with small fields and annular sensitization are discussed.