Fig. 3.

Potentiation of visuocortical contrast responses within focused luminance range (49.2–245.9 cd/m²). A–C: group-averaged (n = 6) blood oxygen level-dependent (BOLD) responses (mean %signal change) for 6 luminance levels and 2 contrast conditions, across early visual cortical regions (V1–V3), displayed with linear function fits. The visuocortical response to a full-field “black” screen (1.2 cd/m²) is represented by a magenta diamond. Shaded symbols and dashed lines represent individual subject luminance response functions. D: group-averaged linear regression slope parameters for each contrast condition, across early visual cortical areas (V1–V3). *P < 0.01; **P < 0.001, significant t test results. Gray symbols and dashed lines represent individual subject slope parameters. Data are means ± SE across participants.