Asymmetrical enhancement of middle-latency auditory evoked fields with aging

We studied the effects of aging on middle-latency auditory evoked fields (P50m), and analyzed their interhemispheric differences. Magnetic responses following tone-burst stimuli to the right ear were measured in groups of 11 younger and 15 elderly subjects. The elderly subjects showed marked asymmetry in the P50m amplitudes. In the elderly group, the mean amplitude of the contralateral P50m was significantly larger (P < 0.0005) than that of the ipsilateral P50m, while no asymmetry was shown in the younger group. The amplitude enlargement in the contralateral P50m showed significant correlation with age (R = 0.60, P < 0.005), while the ipsilateral P50m showed no correlation with age. These results suggest that the contralateral and ipsilateral auditory pathways are affected differently by ageing. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.