Figure 2.

Photosynthetic oxygen production in the brain

(A) Semi-intact head preparation, illustrating the recording of O₂ concentrations in the IV^th ventricle (green electrode) and of superior oblique (SO) nerve spike discharge (black electrode).

(B) Episode (B1) of O₂ concentration recording in the bath chamber (black trace) and IV^th ventricle (green trace) and of concurrent multi-unit SO nerve spiking and mean firing rate (black trace) in darkness and light in a preparation containing C. reinhardtii; the ventricular O₂ concentration increases during illumination with a slower rise (single arrow) and faster decay (double arrow); insets depict SO nerve spiking in darkness (B2) and light (B3) at higher temporal resolution.

(C) Boxplot depicting ventricular O₂ concentrations in darkness (gray bars) and light (yellow bars) in preparations containing wild-types of C. reinhardtii or Synechocystis 6803; ∗∗∗, p < 0.001, Wilcoxon signed-rank test.

(D) Boxplots depicting light-induced changes (Δ) of O₂ concentrations in preparations containing either wild-type (WT) microorganisms (D1) in comparison with photomutant (PM) strains or controls without C. reinhardtii (D2) or Synechocystis 6803 (D3); number of experiments indicated in parentheses. ∗, p < 0.05, ∗∗∗, p < 0.001, Mann Whitney U-test, Bonferroni-corrected; n.s. not significant.