Adaptive focus: Investigating size tuning in visual attention using SSVEP.

This study investigates the size tuning of visual spatial attention using steady-state visual evoked potential (SSVEP) to understand how visual attention efficiently adapts and directs to specific spatial extents. Sixteen participants performed a task involving the rapid serial visual presentation of digits of varying sizes while their brain activity was monitored using electroencephalography. The stimuli flickered at different frequencies, and participants detected target digits at specified sizes. Analysis of SSVEP amplitudes and intertrial phase coherence revealed that visual attention exhibited size tuning with the maximum attentional modulation when the attended size matched the stimulus size. A difference of Gaussian function effectively modeled the facilitation around the attended size and inhibition for adjacent sizes. These findings suggest that visual attention can precisely adjust its focus to enhance processing efficiency, aligning with the zoom lens hypothesis. Our SSVEP study provides strong neural evidence underlying the adaptability of visual attention to varying spatial demands.