Interactions between spatial attention and alertness in healthy adults: A meta-analysis.

Attending to the visuospatial field is paramount for safety. The inability to sufficiently allocate attention in the environment could lead to unfavourable consequences. One's ability to attend quickly to left- and right-sided stimuli can vary depending on the person's level of alertness. A dominant model of this relationship proposes that low alertness is associated with a rightward bias in attention, with increases in alertness shifting attention leftward. The current study sought to synthesise the literature on spatial attention and alertness and identify modulators of this relationship in healthy adults. Nineteen articles meeting inclusion criteria were identified for meta-analysis. A small effect of alertness on spatial bias (d = .302) with no evidence for a systematic publication bias was found. Of the five investigated modulators, namely, the experimental design relative to alertness, direction of alertness manipulation, measurement of alertness, the nature of the spatial task, and handedness, only the latter was identified as a significant modulator of the relationship between alertness and spatial attention. The review's findings tie in with the influential framework by Corbetta and Shulman (2011) and support the idea to increase alertness as a rehabilitation approach to reduce inattention to the left side in neglect patients. Findings also suggest a need for future research to investigate neurological processes that underlie the alertness and spatial attention relationship, and a need to examine the transfer effects of laboratory-based experiments for real-world implications.