Fig. 1.

Experimental stimulus presentation. A: schematic of artificial pupil aperture positioning. B: examples of checkerboard pattern stimuli, varying in overall luminance and contrast (actual stimulus spatial frequency not depicted). C: exemplar single-voxel blood oxygen level-dependent (BOLD) signal time series of a single functional magnetic resonance imaging (fMRI) run from experiment 1. Green and red dashed lines indicate the end of the baseline and adaptation periods, respectively. The remainder of each fMRI run consisted of jittered stimulus presentations for a pair of contrast conditions at all luminance levels. Each row of triangles denotes the onsets of each stimulus contrast type, with shading of each triangle corresponding to the luminance of that particular stimulus.