Category-specific visual agnosia: Lesion to semantic memory versus extra-lesional variables in a case study and a connectionist model

There is a current debate on the causes of category-specific agnosia. The aim of this study was to examine the effects of lesional and extra-lesional variables on object recognition. Extra-lesional variables, such as visual complexity or familiarity, are factors that influence recognition. Using a connectionist model based on Farah and McClelland’s (1991) study, we provide evidence that extra-lesional variables can yield dissociations in the recognition rate of different categories. Furthermore, it is shown that lesional and extra-lesional variables can interact (p<.01) when both are simultaneously modeled. Category-specific agnosia might thus result from complex interactions.