Event-related potential evidence that very slowly presented auditory stimuli are passively processed differently in younger and older adults.

The occurrence of a very infrequent and unattended auditory stimulus is highly salient and may result in an interruption of the frontoparietal network controlling processing priorities. Research has suggested that older adults may be unable to compute the level of salience of unattended stimulus inputs. A multi-channel EEG was recorded in 20 younger adults and 20 older adults. In different conditions, a single 80 dB SPL auditory stimulus was presented relatively rapidly, every 1.5 s or very slowly, every 12.0 s. Participants ignored the auditory stimuli while watching a silent video. When the stimuli were presented rapidly, group differences were not observed for the amplitudes of N1 and P2, which peaked at 100 and 180 ms respectively. When stimuli were presented very slowly, their amplitudes were much enhanced for younger adults, but did not increase for older adults. The failure to observe a large increase in the amplitude of N1 and P2 in older adults for very slowly presented auditory stimuli provides strong evidence of a dysfunction of the salience network in this group.

Auditory Event-related Potentials in Mild Cognitive Impairment and Alzheimer's Disease.

BACKGROUND: Mild cognitive deficits are more likely to occur with increasing age, and become more pronounced for people diagnosed with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Conventional methods to identify cognitive declines (i.e., neuropsychological testing and clinical judgment) can lead to false positive diagnoses of cognitive impairment. Tools such as electroencephalography (EEG) offer additional measures of cognitive processing, indexing the electrophysiological changes associated with aging, MCI and AD. OBJECTIVE: We reviewed the literature on EEG to determine if auditory event-related potentials (ERPs) could distinguish between healthy aging, MCI, and AD. METHOD: We searched two electronic databases (Medline and PyscInfo) for articles published between January 2005 and April 2017. Articles were considered for review if they included: i) participants 60 years of age or older; ii) healthy older adults or those diagnosed with MCI or AD; iii) at least one auditory elicited ERP component. RESULTS: Our search revealed 1532 articles (800 after removing duplicates); 719 were excluded through title/abstract review, and of the 81 remaining articles, 30 satisfied inclusion criteria. All studies compared cognitive function between at least two of the three selected populations. Our findings suggest that the P300 and N200 components may distinguish between healthy cognitive aging, MCI, and AD. CONCLUSION: ERPs may be sensitive to progressive cognitive changes due to MCI and AD. The P300 and N200 may help identify patients who are likely to progress from MCI to AD, and could be a valuable clinical tool.