Dissociable neural mechanisms of selective visual information processing underlie the effects of attention on visual appearance and response bias

There has been a long debate about whether attention can alter visual appearance or whether it just induces response bias. Recently, research studies have provided psychophysical evidence for both theoretical accounts, yet it is unclear how the effects of attention on stimulus appearance and response bias are implemented in the brain. Here, we found that these two effects of attention are associated with different patterns of attentional modulations on different EEG markers of visual information processing. While attention enhanced the multiplicative response gain of the early visually evoked potential (i.e., the P1 component), it induced the baseline shift in alpha amplitude. Quantitative linking models revealed that the response gain amplification of the P1 component could account for attention-induced changes in the psychometric parameter indexing contrast appearance. In contrast, models that included the baseline shift in the alpha amplitude performed better at predicting attention-induced changes in response bias indexed by the baseline offset of the psychometric data and the lateralized readiness potential. Together, our findings suggest that attention can bias both early sensory information and later stages of motor-related processes. Importantly, the effects of attention on contrast appearance and response bias are supported by modulations of different electrophysiological markers that track different stages of visual information processing in the human cortex [No conflicts of interest. Funding was provided by NEI R01 and a James S. McDonnell Foundation award to John T Serences. 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 Sirawaj Itthipuripat.]