Adapting to Change: How the Aging Brain Adapts to Visual Stream Degeneration to Support the Visuospatial Orienting of Attention

Abstract

Every day we are faced with an overwhelming influx of visual information. Visual attention acts as the filtering mechanism that enables us to focus our limited neural resources, by selectively processing only the most relevant and/or salient aspects of our visual environment. The ability to shift attention to the most important events, and/or objects in the surrounding environment is believed to underlie our ability to successfully navigate and interact with our surroundings (Owsley & Mc Gwin, 2004). This ability has been proposed to rely on an interacting network of structures, which include regions of the lateral prefrontal cortex (Asplund, Todd, Snyder, & Marois, 2010; Schall, 2009), working in conjunction with the dorsal visual stream (Lambert & Shin, 2010; Marrett et al., 2011) to guide the deployment of attentional resources. However, recent evidence suggests that the dorsal visual stream undergoes significant levels of deterioration from relatively early on in the ageing process (Mateus et al., 2013; Ziegler et al., 2012). Here, we sought to investigate how the brain adapts to the degeneration of the dorsal visual stream to support the visuospatial orienting of attention in the elderly; as well as, to examine how reducing the luminance contrast of the cue stimuli would influence the recruitment of compensatory neural mechanisms. Our results indicate that despite the slowing of response times, the visuospatial orienting of attention remains relatively well-preserved in older adults, under both high contrast, and low contrast conditions. More importantly, an examination of the neural activity elicited during the cue-target interval, revealed no age-related changes in the amplitude or pattern of neural activation involved in driving these shifts of attention. Overall, the results suggest that not only is the visuospatial orienting of attention maintained in older adults, but that this maintenance does not rely on the recruitment on compensatory neural mechanisms.