More but Less: Enhanced early sensory-evoked responses but reduced attentional focus and delayed sensory integration in healthy aging

Abstract

Visual information processing declines with age. However, it is still unclear if this decline is due to a general decrease in visual sensitivity and or age-related changes in neural mechanisms that support selective attention. Here, we recorded behavioral and EEG while subjects (20-72 years old) performed a variant of attention-cueing Erisken’s flanker tasks. We examined age-related changes in three event-related potentials. These included the P1 and P3 components, reflecting early sensory processing and postsensory decision-making processes respectively. The late midline-frontal negative-going wave (FNinc), known to track the executive function in response to cognitive conflict was also examined. In addition, we used the multivariate analysis of the alpha band activity (i.e., the slow-going EEG oscillations at ~8-12Hz) to reconstruct the spatially specific mental representations related to the cue and target locations on the visual field, examining age-related changes in the spatial scope of visual attention. Overall, when task difficulty was equated across age groups, response times were much slower in the elderly (61-72 years old) compared to the young (20-29 years old) and old adult groups (31-40 years old). Surprisingly, the P1 component’s amplitude evoked by the target display in the elderly was larger compared to the younger groups. That said, the fidelity of alpha-based spatial representations related to the attended location during this early time span significantly dropped and the onset of these alpha-base spatial reconstructions were also delayed as a function of age. These were followed by the increased latencies and the reduced amplitudes of the P3 and FNinc components in the older group. Together, our results suggest that age-related slowing in visual information processing in healthy aging is not due to the decline in the feedforward processing of stimulus inputs but the reduced fidelity of selective attention and the delay in sensory integration and executive function.