Abstract
Attention acts by selectively processing relevant information among vast amount of visual input. Intuitively, top-down attention can only be directed to what we have conscious access of, such as a specific feature, object, or spatial location. Previously in a behavioral experiment we showed that surprisingly voluntary attention can modulate eye-specific visual processing in the absence of explicit knowledge of the eye-of-origin information (Zhang et.al, 2012). In the current study, we aim to provide direct neural evidence for this eye-specific modulation effect of top-down attention. A black mesh grid of 10×10 matrix was presented binocularly as background. Of the 100 grid cells, a quarter of them were luminance modulated at 7.5Hz in one eye, and another quarter were luminance modulated at 10Hz in the fellow eye. In the remaining 50 cells, 25 red and 25 blue dots were presented as monocular cues. The spatial locations of the monocular flickers and cues were mixed and non-overlapping. Observers were instructed to pay attention either to the red or blue dots, to detect occasional changes in dot size. Magnetoen-cephalography (MEG) were recorded to measure steady-state visual evoked responses (SSVER) to the monocular visual flickers. We found that the magnitude of SSVER was significantly larger when the attended dot cues were in the same eye as the visual flicker compared to when they were in different eyes, indicating an eye-specific modulation of neural responses by voluntary attention, despite the absence of awareness of eye-of-origin information.