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May 1992

Failure to Activate the Left Temporoparietal Cortex in DyslexiaAn Oxygen 15 Positron Emission Tomographic Study

Author Affiliations

From the Child Psychiatry Branch (Drs Rumsey and Rapoport and Mss Aquino, King, and Hamburger) and the Section on Clinical Brain Imaging, Laboratory of Cerebral Metabolism (Drs Andreason, Zametkin, and Cohen), National Institute of Mental Health, and Clinical Audiology, Hearing Section, National Institute on Deafness and Communication Disorders, National Institutes of Health (Ms Pikus), Bethesda, Md.

Arch Neurol. 1992;49(5):527-534. doi:10.1001/archneur.1992.00530290115020

• To test the hypothesis of left temporoparietal dysfunction in dyslexia, suggested by neuropsychological and neuropathologic data, cerebral blood flow was measured with positron emission tomography in 14 right-handed men with severe developmental dyslexia (mean [SD] age, 27 [5] years; median reading level, fifth grade) and 14 matched controls at rest and during an auditory phonologic task (rhyme detection) and an auditory attention task involving the detection of target tones. As expected, normal readers activated left temporoparietal cortex during rhyme detection but not during the nonphonologic attentional task. Dyslexic men failed to activate those left temporoparietal regions activated in controls during rhyme detection but did not differ from controls in these regions during rest or attentional testing. Thus, the expected left temporoparietal dysfunction was demonstrated only when specific probes for these regions were employed.