RECEPTIVE-FIELD CHANGES AFTER STROKE-LIKE CORTICAL ABLATION - A ROLE FOR ACTIVATION DYNAMICS

The reorganization of neural activity that takes place after stroke is of paramount importance in producing functional recovery. Experimenta l stroke models have suggested that this reorganization may have two p hases, but physiology alone cannot fully resolve what causes each phas e. Computer modeling suggests that these phases might involve an initi al change in dynamics occurring immediately, followed by synaptic plas ticity. We combined physiological recording from macaque middle tempor al cortex (area MT) with a neural network computer model to examine th is first phase of altered cortical function after a small, experimenta lly induced cortical lesion. Major receptive field (RF) changes seen i n the first few days postlesion included both expansion and contractio n of receptive fields. Although only expansion could be reproduced in an initial model, addition of inhibitory interneuron loss in a ring ar ound the primary ablation, suggested by immunohistochemical examinatio n, permitted contraction to be replicated as well. We therefore predic t that this immunochemical observation reflects an immediate extension of the lesion rather than a late response. Additionally our model suc cessfully predicted a correlation between increased firing rate and RF size. Our model suggests that activation dynamics alone, without anat omic remodeling, can cause the large receptive field changes that allo w the rapid behavioral recovery seen after middle temporal lesions.