Sustained attention operates via dissociable neural mechanisms across different eccentric locations

In primates, foveal and peripheral vision have distinct neural architectures and functions. However, it has been debated if selective attention operates via the same or different neural mechanisms across these different eccentric locations. We hypothesized that the discrepancies between past results arose in part from the differences in neural signals used to index attentional modulations and the differences in task difficulty across eccentricities. Here, we measured three EEG indices of visual processing, while human subjects performed a visual attention task, where they either attended to the fixation or to the visual stimuli presented at different eccentricities. These EEG indices include the amplitudes of the steady-state visually evoked potentials (SSVEPs), the sustained negative deflection (SND), and the alpha band activity. Critically, we equated task difficulty across the different attention conditions and eccentricities. Overall, the amplitudes of these neural markers reduce as a function of eccentricity, reflecting changes in cortical magnification. However, they expressed totally different patterns of attentional modulations across eccentricities. The SSVEP exhibited prominent attentional gain modulations at the peripheral locations, but attentional modulations were significantly reduced at the parafoveal locations. In contrast, the SND showed relatively similar levels of attentional modulations across the parafoveal and the peripheral locations. On the other hand, alpha band activity exhibited significant attentional modulations only at the peripheral locations, which relied primarily on the relative differences between the contralateral and ipsilateral signals. Taken together, these results suggest that sustained visual attention comprises multiple biophysical processes that differentially impact sensory information processing across eccentricities. [This project was funded by NEI R01 to GW. This project was also funded by the National Research Council of Thailand grant (fiscal year 2021), the Thailand Science Research and Innovation Basic Research grant (fiscal year 2021 under project numbers 64A306000016 and fiscal year 2020 under project number 62W1501), the Asahi Glass Foundation grant, the research grant from the Research & Innovation for Sustainability Center, Magnolia Quality Development Corporation Limited, Thailand, the KMUTT Partnering initiative grant (fiscal year 2021), and the startup fund for junior researchers at King Mongkut’s University of Technology Thonburi (KMUTT), and the KMUTT’s Frontier Research Unit Grant for Neuroscience Center for Research and Innovation to SI.]