Dynamic random noise shrinks the twinkling aftereffect induced by artificial scotomas

Physiological alterations in cortical neurons are induced during adaptation to an artificial scotoma, a small homogeneous patch within a dynamic rando m noise or patterned background. When the dynamic noise is replaced by an e quiluminant gray background, a twinkling aftereffect can be seen in the loc ation of the artificial scotoma. Following binocular adaptation, we discove red that the perceived size of the twinkling aftereffect was:dramatically s maller than the inducing artificial scotoma. Dichoptic adaptation induced s hrinkage in the twinkling after effect that was similar to that found after binocular adaptation, suggesting that the twinkling aftereffect and its sh rinkage both have cortical origins. We speculate that this perceptual shrin kage may reflect the interaction between two cortical mechanisms: a twinkli ng aftereffect mechanism that spreads throughout the artificial scotoma, an d a filling-in mechanism that has a greater influence at the edges of the a rtificial scotoma and spreads inwards. (C) 2000 Published by Elsevier Scien ce Ltd. All rights reserved.