Interhemispheric Effects of Simulated Lesions in a Neural Model of Letter Identification

Effects of callosal lesions in a model of letter perception

“…However, our sense from the present study and other recent computational modeling studies is that the computational evidence is increasingly supportive of the notion that callosal influences are excitatory. Not only do excitatory callosal influences explain the cerebral metabolic changes of diaschisis seen with stroke and callosal sectioning, but they have also provided a better account for some poststroke clinical findings (e.g., Rizzo & Robin, 1996) when these have been studied computationally (Shevtsova & Reggia, 2000). But if one accepts this hypothesis, it leaves open the question of how marked lateralization, such as occurs with language, can occur in the context of excitatory callosal influences, because in the past, qualitative hemispheric specialization has consistently proven easier to obtain in computational models when callosal influences are assumed to be inhibitory.…”

“…In this work, we use a recently created neural model of letter identification consisting of left and right visual hemispheric regions interacting via a simulated corpus callosum. This model has previously been used to investigate conditions under which underlying asymmetries can lead to functional lateralization (Shevtsova & Reggia, 1999) and to demonstrate the extent to which, following unilateral focal damage to one cerebral hemisphere, the opposite intact hemisphere can be responsible for recovery (Shevtsova & Reggia, 2000). The effects of callosal sectioning are now studied in the acute (just following the lesion) and chronic (after retraining and recovery) phases, focusing on determining how the model's behavior differs, following lesions to the corpus callosum, depending on whether callosal influences are assumed to be excitatory or inhibitory.…”

Neurocomputational models of the remote effects of focal brain damage

“…Accordingly, several versions of each of these three models were subjected to systematic lesioning studies (a lesion is a region of damage) [46,[52][53][54]. Each lesion was introduced into an intact model by clamping a subset of elements in one hemispheric region to be nonfunctional.…”