Presaccadic attention depends on eye movement direction and is related to V1 cortical magnification

Abstract

With every saccadic eye movement, humans bring new information into their fovea to be processed with high visual acuity. Notably, perception is enhanced already before a relevant item is foveated: During saccade preparation,presaccadic attentionshifts to the upcoming fixation location, which can be measured via behavioral correlates such as enhanced visual performance or modulations of sensory feature tuning. The coupling between saccadic eye movements and attention is assumed to be robust and mandatory, and considered a mechanism facilitating the integration of pre- and post-saccadic information. However, until recently it had not been investigated as a function of saccade direction. Here, we measured contrast response functions during fixation and saccade preparation in male and female observers and found that the pronounced response gain benefit typically elicited by presaccadic attention is selectively lacking before upward saccades at the group level – some observers even showed a cost. Individual observers’ sensitivity before upward saccades was negatively related to their amount of surface area in primary visual cortex representing the saccade target, suggesting a potential compensatory mechanism that optimizes the use of the limited neural resources processing the upper vertical meridian. Our results raise the question how perceptual continuity is achieved and upward saccades can be accurately targeted despite the lack of –theoretically required– presaccadic attention.Significance StatementWhen we make a saccadic eye movement to a target location in the visual field, perception improves at the saccade target, already before the eyes start moving. This benefit afforded by presaccadic attention is thought to be mandatory and independent of eye movement direction. We show that this is not the case; moving our eyes horizontally or downwards, but not upwards, enhances contrast sensitivity. At the neural level, however, humans with less V1 cortical tissue representing the target location for upwards saccades have some presaccadic enhancement. The finding that presaccadic attention is dependent upon eye movement direction challenges the view that the presaccadic benefit is automatic and mandatory in nature.