Sounds, words, sentences: age-related changes across levels of language processing.

Age-related changes in sensory, lexical, and sentence processing were examined and compared using event-related potentials (ERPs) recorded as young and elderly participants listened to natural speech for comprehension. Lexically associated and unassociated word pairs were embedded in meaningful or syntactically legal but meaningless sentences. Early, general sensory, and attention-related responses (N1, P2) were delayed by about 25 ms for older participants, but later components indexing semantic processing (N400) were not delayed.

Electrophysiological analysis of context effects in Alzheimer's disease.

Event-related potentials elicited by semantically associated and unassociated word pairs embedded in congruous and semantically anomalous spoken sentences were recorded from patients with Alzheimer's disease (AD) and healthy older and young controls as a means of examining the nature, time course, and relation between word and sentence context effects. All groups demonstrated lexical priming in nonsensical sentences, but it was earlier in the young (200-600 ms) than in the older controls (600-800 ms), and even later in the probable AD patients (800-1,000 ms). Moreover, processing in both the elderly and AD groups benefited disproportionately from a meaningful sentence context.