(ai) Evoked visual responses to gratings (100% contrast) in anesthetized (solid traces) and awake mice (stippled traces). Control condition (V, black), condition with concurrent photostimulation of the DRN (Vph, dark blue). Light blue traces depict spontaneous activity with photostimulation (Sph), dotted black traces around zero show baselines without any input. Green and black circles mark the amount of Sph at time to peak (tpk), i.e. the time where Vph reaches maximum values (green = awake (aw): -0.09±0.03, n=5, p<0.01, one-sample t test); black = anesthetized (an): -0.17±0.03, n=18, p<0.001, one-sample t test); g refers to the 5-HT-induced gain (i.e. the inverse of c, ); gaw<gan with gaw : 1.35±0.2, n=5 and gan : 2.20±0.7 n=18, p<0.01, two-sample t test. Rectangle at right is a magnified view of the area marked in left panel. (aii) Traces shown in ai, normalized by the ratio equal to their corresponding g . Magnified view at right demonstrates the resulting relative change of Sph values after normalization. Note the difference between the awake and the anesthetized state: transparent dots (copied from ai) are values before normalization and solid dots values after normalization. (bi), Relative weights of evoked component (gray bars) at each grating contrast in comparison to the weight of the baseline component (blue bars) in the anesthetized state after normalization (Equation 4 in main text). (bii) Same as bi in the awake state. (biii) same as bii, assuming (i.e. simulating) the amount of Sph in the awake state (Sph aw) being equal to the value of Sph in the anesthetized state (Sph an=-0.17). Note that also in this case, the weight of the spontaneous component in the awake state (g×Sph)aw remains significantly smaller (-0.22±0.03, n=5, blue bars in biii) than the spontaneous component (g×Sph)an in the anesthetized state (-0.36±0.11, n=18, blue bars in bi), p<0.001 two-sample t test. ***p<0.001, **p<0.01, and *p<0.05, one-sample and two-sample t test.