Occipital activation by pattern recognition in the early blind using auditory substitution for vision.

This PET study aimed at investigating the neural structures involved in pattern recognition in early blind subjects using sensory substitution equipment (SSE). Six early blind and six blindfolded sighted subjects were studied during three auditory processing tasks: a detection task with noise stimuli, a detection task with familiar sounds, and a pattern recognition task using the SSE. The results showed a differential activation pattern with the SSE as a function of the visual experience: in addition to the regions involved in the recognition process in sighted control subjects, occipital areas of early blind subjects were also activated. The occipital activation was more important when the early blind subjects used SSE than during the other auditory tasks. These results suggest that activity of the extrastriate visual cortex of early blind subjects can be modulated and bring additional evidence that early visual deprivation leads to cross-modal cerebral reorganization.