Effects of visual deprivation on the organization of the semantic system.

Early onset blindness provides a lesion model to investigate whether experience-dependent mechanisms subtend the functional anatomy of semantic retrieval. In particular, visual deprivation might alter the neural systems underlying retrieval of semantic information that is acquired via visual experience. Using functional MRI, we demonstrate that both early blind and sighted subjects activate a left-lateralized fronto-temporal 'core' semantic retrieval system and show common effects for retrieval of visually experienced semantic information. However, irrespective of the type of semantics, blind subjects activate additional extrastriate regions, which are coupled with frontal and temporal semantic regions. The resilience of semantic retrieval responses to visual deprivation suggests a considerable degree of innate and epigenetic specification of the semantic system. In contrast, the exuberant functional connectivity between extrastriate and 'core' semantic retrieval regions might be explained by abnormal pruning processes during early neurodevelopment.