Auditory sensory memory impairment in Alzheimer's disease: an event-related potential study.

Auditory event-related potentials (ERP) were recorded from 10 healthy older subjects and 9 patients with Alzheimer's disease (AD) to investigate whether auditory sensory memory is impaired in AD. Standard (85%) and deviant (15%) tones were presented in random order with interstimulus intervals (ISI) of 1 s or 3 s in separate blocks. Deviant tones elicited a specific ERP component called mismatch negativity (MMN) which reflects automatic stimulus change detection and thus presumably, the neural basis of sensory memory in audition. The MMN amplitude decreased as a function of the ISI more in the AD group than in the control group. This suggests that the memory trace decays faster in the AD patients than in age-matched healthy controls.