The temporal window of integration in elderly and young adults

Integration of information across time is an essential part of auditory processing. Evidence from a variety of experiments support the notion of an approximately 200-ms long time window following the onset of a sound, during which a unitary sound representation is formed (the temporal window of integration, TWI). The temporal resolution in the auditory system is assumed to decrease with aging suggesting that the duration of the TWI may be longer in elderly than young adults. The TWI duration was assessed in young and elderly adults using the oddball paradigm in which a regular auditory event (standard) is occasionally exchanged for a different event (deviant). Previous studies showed that when the stimulus onset asynchrony (SOA) exceeds the duration of the TWI, two successive deviations occurring infrequently in a repetitive sound sequence elicit two separate mismatch negativity (MMN) event-related brain potentials. However, only one MMN is elicited when the SOA is shorter than the TWI. Experiment 1 tested MMN elicitation for the second of two successive deviant sounds as a function of the SOA. Experiment 2 used the sound omission paradigm, in which MMN is only elicited by omissions when the SOA is shorter than the TWI. Again, MMN elicitation was tested by infrequent tone omissions as a function of the SOA. Results showed no significant differences between elderly and younger participants as a function of SOA. This suggests that the duration of the TWI is approximately between 200 and 250 ms in both groups of subjects. On the other hand, the lower MMN amplitudes elicited by frequency deviation in the elderly compared with the younger participants suggest that the specificity of frequency representation deteriorates with aging.