An event-related potential evaluation of involuntary attentional shifts inyoung and older adults

Involuntary shifts in attention to irrelevant stimuli were studied in elder ly and young volunteers during a dichotic-listening task. Event-related pot entials and behavioral measures were recorded. Volunteers heard pairs of to nes presented with 2 different stimulus onset asynchronies (SOAs). To-be-ig nored tones were presented to the left car, followed by to-be-attended tone s to the right ear. Left-ear tones were a frequent standard (700 Hz) and an infrequent small (650 Hz) and large (500 Hz) deviant. Right-ear tones (150 0 Hz) were presented with 2 equiprobable intensities. Volunteers responded to the lower intensity stimulus. Behavioral performance was impaired at the short SOA when to-be-ignored large deviants preceded to-be-attended target s, but more so for the elderly volunteers. Large deviants also elicited the mismatch negativity (MMN) and P3a for both age groups. It was concluded th at the more impaired behavioral performance observed for the elderly was du e to greater sensitivity to output from the MMN system by a frontal lobe sy stem responsible for the maintenance of attentional focus.