Response processing during visual search in normal aging: the need for more time to prevent cross talk between spatial attention and manual response selection.

It is still not well known whether the age-related behavioural slowing observed during visual search is due to changes in the allocation of attention, in response activation patterns, or to a combination of both. To help in clarifying it, attention-related (N2 posterior contralateral; N2pc, and N2 central contralateral; N2cc) and response-related (Motor Potential; MP, and Reafferent Potential; RAP) event-related potentials (ERPs) were obtained in healthy young and older participants executing a visual search task. Age was associated with N2pc and N2cc longer latencies, earlier MP onsets and longer MP rise times. Lower N2pc, higher MP and lower RAP amplitudes were also observed. Results suggest that older participants need more time to allocate spatial attention onto the target (N2pc) and to prevent cross talk between response selection and attention direction (N2cc), and that they are slower and need higher cortical activation when preparing and executing correctly selected responses (MP).