Age-related top-down suppression deficit in the early stages of cortical visual memory processing

TLDR

The study used EEG to investigate how the inhibitory deficit and processing‑speed hypotheses relate to cognitive aging. EEG recordings during visual working‑memory encoding were analyzed, and older adults were subdivided by working‑memory performance to link early suppression deficits to memory outcomes. Older adults show a delayed, selective deficit in suppressing irrelevant visual information early in processing, leading to poorer memory of relevant items and supporting an interaction between inhibition and processing‑speed decline.

Abstract

In this study, electroencephalography (EEG) was used to examine the relationship between two leading hypotheses of cognitive aging, the inhibitory deficit and the processing speed hypothesis. We show that older adults exhibit a selective deficit in suppressing task-irrelevant information during visual working memory encoding, but only in the early stages of visual processing. Thus, the employment of suppressive mechanisms are not abolished with aging but rather delayed in time, revealing a decline in processing speed that is selective for the inhibition of irrelevant information. EEG spectral analysis of signals from frontal regions suggests that this results from excessive attention to distracting information early in the time course of viewing irrelevant stimuli. Subdividing the older population based on working memory performance revealed that impaired suppression of distracting information early in the visual processing stream is associated with poorer memory of task-relevant information. Thus, these data reconcile two cognitive aging hypotheses by revealing that an interaction of deficits in inhibition and processing speed contributes to age-related cognitive impairment.