Does aerobic fitness moderate age-related cognitive slowing? Evidence from the P3 and lateralized readiness potentials

Reaction time (RT) slowing occurs among older adults, although it remains unclear whether general or specific aspects of information-processing are implicated in this phenomenon. Aerobic fitness moderates age-related RT slowing, although it is unknown whether fitness benefits earlier versus later stages of information-processing. To test these hypotheses, 40 younger and 43 older adults classified by level of aerobic fitness were tested using a visual oddball paradigm to assess behavioral measures of RT and accuracy along with the P3 wave and lateralized readiness potential (LRP) to index stimulus categorization and response selection and execution processes, respectively. Older adults had slower RT, decreased P3 amplitude, and increased P3 latency and LRP amplitude, suggestive of generalized age-related cognitive slowing decline. While aerobic fitness was significantly correlated with median RT and P3 latency across the entire sample, these correlations did not persist when adjusting for age. Subsequent moderation analysis also failed to support an influence of aerobic fitness on any of the cognitive outcomes. These findings indicate that, at least in simple discrimination tasks, aging is associated with slower processing that occurs proximal to stimulus categorization and extends to motor response and execution processing. These age-related deficits, however, are not moderated by aerobic fitness.