The influence of different types of auditory change on processes associated with the switching of attention in younger and older adults.

Potentially highly relevant but unattended auditory stimuli may result in attention capture. The detection of stimulus change is associated with two event-related potentials: the deviant-related negativity (DRN), whose amplitude varies with the extent of change, and the P3a, which is elicited only by stimuli deemed to be highly relevant. In the present study, younger adults (aged 18-30 years) and older adults (aged 65-73 years) were presented with to-be-ignored auditory stimuli while engaged in a visual task. The auditory stimuli consisted of frequently presented standards and six different rarely presented deviants. In older adults, the amplitude of the DRN varied with the extent of deviance: it was significantly larger to the white noise and environmental sound deviants. A large P3a was elicited by these in younger adults but was much reduced in older adults. The DRN results suggest that older adults are able to compute saliency level of unattended stimulus input at an early stage of processing. However, the attenuated P3a results in older adults suggest that a potentially highly salient stimulus is not given sufficient priority to result in a switch of attention from current cognitive demands.