Regional cerebral blood flow during signed and heard episodic and semantic memory tasks.

Ten deaf participants and 10 normal hearing participants performed 2 memory tasks during which their regional cerebral blood flow was measured with a high-resolution system. The deaf participants solved an episodic memory (i.e., recognition of words) and a semantic memory (i.e., classification of items into categories) task presented by means of sign language; the same material was presented to the hearing participants who heard the stimulus lists. The specific hypothesis that signed episodic recognition tasks would activate posterior, right-hemisphere cortical areas was supported. Expectedly, the remaining 3 memory activations were mainly located in the left hemisphere. Data from recent positron emission tomography studies suggest that one challenge for future research is to assess the relative localization for encoding and retrieval of signed episodes.