Bitemporal lesions dissociate auditory evoked potentials and perception |
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Authors: | D L Woods R T Knight H J Neville |
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Institution: | 1. Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, NY, New York, United States of America;2. Department of Environmental Health & Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States of America;3. Fundación Investigación Clínico de Valencia-INCLIVA, Area of Cardiometabolic and Renal Risk, Valencia, Spain;4. Department of Statistics and Operational Research, University of Valencia, Valencia, Spain;5. MedStar Health Research Institute, Hyattsville, MD, United States of America;6. Department of Medicine, Georgetown University School of Medicine, Washington, DC, United States of America;7. Missouri Breaks Industries Research, Inc., Eagle Butte, SD, United States of America;8. Institute of Chemistry - Analytical Chemistry, University of Graz, Austria;9. Texas Biomedical Research Institute, San Antonio, TX, United States of America |
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Abstract: | We studied auditory evoked potentials (AEPs) in an 82-year-old female patient who became suddenly deaf following the second of two strokes. The patient showed markedly elevated pure tone thresholds, was unable to discriminate sounds and could not understand speech. Brain-stem auditory evoked potentials (BAEPs) were normal. CT scans revealed bilateral lesions of the superior temporal plane which included auditory cortex. Two experiments were performed. In the first, tones, complex sounds and speech stimuli were presented at intensities above and below the patient's perceptual threshold. P1, N1 and P2 components were elicited by each of the stimuli--whether or not they were perceived. In particular, stimuli presented below threshold evoked large amplitude, short latency responses comparable to those produced in a control subject. In a second experiment, the refractory properties of the N1-P2 were examined using trains of tones. They were also found to be similar to those of normal subjects. Shifts in the pitch of the tones near the end of the train (when refractory effects were maximal) evoked N1-P2s with enhanced amplitudes, although the change in pitch was not perceived by the patient. In both experiments AEP scalp topographies were normal. The results suggest that bitemporal lesions of auditory cortex can dissociate auditory perception and long-latency auditory evoked potentials. A review of evoked potential studies of cortical deafness suggests that the neural circuits responsible for N1-P2 generation lie in close proximity to those necessary for auditory perception. |
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