Visual working memory capacity is limited by two systems that change across lifespan

Abstract

• Visual working memory capacity is limited by two systems. • Hemispheric specific representational systems establish visual representations. • The active maintenance system sustains representations in absence of stimuli. • The active maintenance cannot support the full capacity of both representational systems. • The capacities of both systems change throughout development and healthy aging. To better understand the sources of visual working memory limitations we explore the possibility that its capacity is limited by two systems: a representational system that enables formation of independent representations of visual objects, and an active maintenance system that enables sustained activation of the established representations in the absence of external stimuli. A total of 392 participants took part in four experiments in which they were asked to maintain orientation of items presented to the left, right or both visual hemifields. In all four experiments participants were able to maintain more items when they were distributed across both versus one visual hemifield, consistent with the proposal that bilateral display enables utilization of representational capacities of both hemispheres. Bilateral capacity, however, did not reach the combined representational potential of both hemispheres, indicating that the capacity is further limited by a second, unitary active maintenance system. Our study further suggests that both systems’ capacities change throughout the lifespan very similarly. They both increase through development, reach a peak at the same age and decrease in healthy aging. This indicates that systems beyond executive processes, which receive most attention in the literature, are contributing to the decline in working memory in healthy aging.