Abstract
Eyelids are potent filters of visual information. Despite its strong attenuation factor, our eyelids still pass light, allowing the visual system to potentially process some information in visual scenes. Subjective experience with high luminance visual stimuli suggests that even with closed eyes changes in luminance are detectable. However, the specific impact of eye closure on processing within the early visual system remains largely unknown. To better understand visual processing when eyes are shut, we use functional magnetic resonance imaging (fMRI) to assess BOLD responses to a full-field flickering stimulus at high (100%) and low (10%) temporal contrasts, while participants viewed the stimuli with their eyes open and eyes closed. Interestingly, we discovered a qualitatively distinct pattern of effects within the visual thalamus and visual cortex. Replicating previous work in the lab, we found that with eyes open, BOLD responses decreased in V1 and V2 with increasing temporal contrast, but no significant modulation in V3 or the lateral geniculate nucleus (LGN). However, with eyes closed, the LGN and V1-V3 showed greater responses to high temporal contrast stimuli. Analysis of eccentricity preferences, as measured with independent pRF mapping, demonstrate stronger differences between high and low amplitude stimuli for both eyes closed and eyes open respectively in more peripheral- compared to foveal-tuned voxels. Because we may be inducing mesopic vision conditions where rods and cones are both active, the greater distribution of rods with greater eccentricities may account for stronger peripheral activation. Our findings suggest a qualitative difference in visual processing with eyes closed compared to eyes open that is not simply an attenuation of visual processing. These results inform the neuronal processing of visual stimuli in states where the eyes are closed, such as in sleep states.