a, b The proportions of pixels with pH changes defined as actual changes in brain pH were pooled across all nine experiments performed in mouse brains (a) or all three experiments performed in HEPES-buffered saline (b). As described in Fig. 3, a pixel with a pH change that exceeded the 95% confidence interval values based on the mean delta pH value of all HEPES-buffered saline experiments (n = 3) was defined as showing an actual change in brain pH. Thus, the proportions of such pixels in the HEPES-buffered saline experiments (b) suggest the false-positive rate of this definition. In the box and whisker plots, the center line indicates the median; the box defines the 25–75th percentiles; the whiskers represent minimum and maximum values while the red crosshairs represent outliers. Filled circles are individual data points. Green plots correspond to HEPES-buffered saline while blue plots correspond to mouse brains. Source data are provided as a Source Data file.