Alzheimer's disease affects parallel processing between the auditory cortices

AUDITORY evoked magnetic fields (AEFs) were recorded from 11 patients with Alzheimer's disease (AD) and 11 age-matched controls using the 122-channel whole-head magnetometer. Auditory stimuli were monaurally presented with interstimulus intervals (ISI) of 0.5 and 2.5 s in different blocks. The peak latencies of P50m and N100m responses were significantly longer in AD patients than in controls over the ipsilateral but not over the contralateral auditory cortex with respect to the ear stimulated. This finding suggests that parallel auditory processing is impaired between the auditory cortices in AD patients. The present MEG measurement might provide an objective index to evaluate auditory dysfunction in AD.