Lesion effects in a bihemispheric letter-identification model

The effects of simulated lesions on a bihemispheric letter-identification model are examined in the acute and chronic phases under various assumptions about hemispheric asymmetries, callosal influence, and lesion size and side. In the acute phase, generally a “mass effect” is seen: post- lesion performance of the full model worsens as lesion size increases. Up to a lesion size of 80%, both hemispheres usually participate in recovery with more active participation of the damaged hemisphere, and in most cases, full recovery is achieved. For lesions of more than 80%, recovery is partial and due to improvement in the non-damaged hemisphere. Most importantly, the model demonstrates participation of the intact hemisphere in the recovery process as a function of pre-existing lateralization and lesion size, indicating that interpretation of experimental work should take these factors into account