FIGURE 4.

Distal to proximal skin temperature gradient (DPG) response and dynamics during light exposure. (A; left) Effect of light condition on the DPG. DPG absolute values are expressed relative to dim light (min 0) values, in normalized units (n.u.). (B; middle) Variation of DPG during the protocol. Each pulse, corresponding to the average over the four light conditions, is shown in plain lines. DPG absolute values are expressed as a change from their dim light level at 19:10, in normalized units (n.u.). Gray bars show the 10-min dim-light episode before each light exposure. (C; right) Dynamics of the DPG during the 50-min light exposure. DPG absolute values are expressed relative to dim light (min 0) values, in normalized units (n.u.). Schematic representation of the light stimulus is shown above the time (min) axis (right column). The gray circle indicates dim light. The blue- or red-enriched white light condition is illustrated by the blue circle. The yellow circle inside the blue circle represents the presence of the central light spot (C1 or C2) in addition to the full field exposure. The two vertical dotted lines indicate the light transitions, from dim light to blue- or red-enriched white light, and to addition of C1 or C2. Values represent the mean ± s.e.m. Dotted horizontal lines indicate the baseline dim-light level. ^‡Significant pairwise comparison between light conditions. ^∗Significant pairwise comparisons between min 1–42 time-points. P-values of all post hoc pairwise time comparisons are given in Supplementary Table 3.