2023 Volume 63 Issue 1.2 Pages 1-11
Previous studies reported that attention oriented to the lower visual field (LVF) facilitated visual processing of the stimuli in the area compared with attention oriented to the upper visual field (UVF). This study explored how the spatially oriented attention to the LVF relates to the better visual performance in the area, that is, LVF superiority, using steady-state visual evoked potentials (SSVEPs) to a task-irrelevant flicker as an index of attention to the irrelevant information. Attention to a flickering stimulus has been shown to increase SSVEPs amplitude, and averting attention from the flickering stimulus decreases it. In the experimental trials, the participants underwent a visual discrimination task that the visual stimuli were presented in either of the LVF or UVF of a computer display. During the trials, an LED was kept flickered on either the right or left edge of the display independently of the stimuli of the visual discrimination task, and SSVEPs to the flickering LED were analyzed. The results showed that under the situation that the stimuli were presented in the LVF, performance of the discrimination task was better and the amplitude of SSVEPs to the task-irrelevant flicker was larger, compared with the situation that the stimuli were presented in the UVF. These vertical anisotropies, i.e. difference between the UVF and LVF, were consistent with the explanation that spatially oriented attention to the LVF could reduce perceptual load in the visual processing tasks compared with spatially oriented attention to the UVF. This study suggests that the LVF superiority in visual tasks is not a result of reduced attention to task-irrelevant information.