Cue-related processing accounts for age differences in phasic alerting.

Alertness is fundamental for the efficiency of information processing. A person's level of alertness refers to the system's state of general responsiveness and can be temporarily increased by presenting a neutral warning cue shortly before an event occurs (Posner and Petersen, 1990). However, effects of alerts on subsequent stimulus processing are less consistent in older than in younger individuals. In this study, we investigated the neural underpinnings of age differences in processing of auditory alerting cues. We measured electroencephalographic power and phase locking in response to alerting cues in a visual letter report task, in which younger but not older adults showed a cue-related behavioral advantage. Alerting cues evoked a significant increase in power as well as in inter-trial phase locking, with a maximum effect in the alpha frequency (8-12 Hz) in both age groups. Importantly, these cue-related increases in phase locking and power were stronger in older than in younger adults and were negatively correlated with the behavioral alerting effect in the older sample. Our results are in accordance with the assumption that older adults' neural responses may be more strongly driven by external input and less variable than younger adults'. A stronger neural response of the system to the auditory cue may have hindered older adults' effective use of the warning signal to foster processing of the following visual stimulus.