Exploring Visual Attention Functions of the Human Extrageniculate Pathways Through Behavioral Cues

Over the past few decades, evidence has accumulated showing that, at subcortical levels, visual attention depends partly on the extrageniculate neural pathways, that is, those pathways that bypass the lateral geniculate nucleus and circumvent the primary visual cortex. Working in concert with neuroscience, experimental psychology has contributed considerably to the understanding of the role these pathways play through the use of 3 behavioral cues: nasal-temporal asymmetries, responses to S-cone stimuli, and responses to perceptually suppressed stimuli. In this article, after presenting the extrageniculate pathways and the role of each of the component structures in visual attention, we review findings from studies that have used these behavioral cues, as well as what they tell us about the role of the extrageniculate pathways in visual attention. We conclude that nasal-temporal asymmetries and responses to S-cone stimuli are plausible probes of extrageniculate functions, because they are consistent with neurophysiological, neuropsychological, and neuroimaging findings. By contrast, despite promising perspectives, the literature is yet too scarce for responses to perceptually suppressed stimuli to be considered as a plausible probe of extrageniculate-dependent attention functions.