RIGHT FRONTOTEMPORAL ACTIVATION BY TONAL MEMORY IN DYSLEXIA, AN O-15 PET STUDY

A prior study documented the failure of dyslexic men to activate left temporoparietal cortex during phonologic processing. Because of report s of an anomalous right planum temporale in developmental dyslexia, th e functional implications of which are unknown, this study examined th e ability of dyslexics to activate right temporal cortex. Regional cer ebral blood flow was measured in 15 right-handed dyslexic men during r est and during a tonal memory task expected to activate right-sided co rtex in controls. A matched control sample (n = 18) showed significant activation of several right frontotemporal regions as well as of left temporal cortex. In contrast, severely dyslexic men activated fewer r ight frontotemporal regions, while making many more errors than contro ls, but showed normal activation of left mid to anterior temporal cort ex. These results support hypothesized underlying deficits in rapid te mporal processing and possible involvement of right (in addition to le ft) temporal cortex in severe dyslexia.