[Late acoustically evoked potentials--effect of age, sex and different study conditions]

54 healthy volunteers (25-82 years) were studied in an "auditory oddball" event-related potential paradigm. The tones (80%, 800 Hz; 20%, 1,600 Hz) were presented via two earphones in an randomized form. The rare tones were counted by the volunteers. Each volunteer was tested with the conditions, "eyes open" and "eyes closed". We found: An increase of the P3-latency of 0.92 ms/year (280 ms in the age of 20 years), and a decrease of P3-amplitude of 0.14 microV/year (17.2 microV in the age of 20 years). In contrast to other studies, the amplitude of the P2-wave (12.8 ms in the age of 20 years) and the latency of the P2-wave (160 ms in the age of 20 years) was not influenced by age. Females showed greater amplitudes of the P2- and P3-components. Females showed a clearly smaller increase on P3-latency with age (0.25 ms/year, starting with 296 ms in the age of 20 years) than males (1.3 ms/year, starting with 272 ms in the age of 20 years). The condition "eyes open" or "eyes closed" did not influence the late auditory evoked potentials. The results were interpreted by taking into account the great sensitivity of the late evoked potentials for changes of the state, which can be defined as well on the neurophysiological level as on the behavioural level.