During control blocks subjects were presented unintelligible stimuli matched to the nouns in intensity, duration, and spectral content, which they were instructed to ignore. The stimuli were created by a male voice reading nouns into a computer. Extraneous noise before and after each word was erased. Sound intensities for all words were equalized. The nouns were randomly assigned to eight different lists, one for each fMRI run. No noun was repeated within or across runs. Otherwise, unused two or three syllable nouns were time reversed to create the control stimuli, which were constant within each run but varied across runs.
On average, subjects recalled more than 60 percent of covertly generated verbs from a preceding run. Early blind recalled significantly fewer verbs. The fMRI results from these two subjects were indistinguishable from other early blind subjects. Average reaction times for recalled verbs were significantly shorter for sighted subjects. This difference primarily reflected greater consistency in the performance of nearly all sighted subjects compared with several blind subjects. The predominant reaction times even in the latter were similar to those observed in the sighted group. Despite these differences, all subjects reported having no difficulty doing the task.
The results confirm prior reports of visual cortex activation in blind persons performing nonvisual tasks. Auditory tasks were used i
Contact: Donna Krupa
American Physiological Society