Preserved stimulus deviance detection in Alzheimer's disease

Aging attenuates automatic auditory discrimination to duration change, wher eas frequency change detection is relatively unimpaired in aging and in Alz heimer's disease (AD). Here we studied with a whole-head magnetometer wheth er cortical auditory discrimination to duration change as shown by magnetic mismatch negativity (MMNm) response is impaired in AD. Twenty AD patients with mild to moderate cognitive impairment and 18 age-matched healthy subje cts were monaurally presented a sequence of frequent standard tones embedde d with occasional deviants with shorter duration. MMNm was significantly de layed in the left hemisphere ipsilaterally to the ear stimulated in the pat ient group, whereas the MMNm amplitudes over both hemispheres were quite si milar in both groups. This suggests that although MMNm is delayed in the le ft hemisphere, the automatic discrimination to duration change in the audit ory cortex is not attenuated in the early stages of AD. NeuroReport 12:1649 -1652 (C) 2001 Lippincott Williams & Wilkins.