Top left: comparison between the raw (dots with yellow to blue colour scale) and corrected (red dots) log() calcium activity index, as described in the text. Bottom left: differences between the raw and corrected log() time series. We clearly see that the slow increase in the activity index followed by sudden jumps at each warm-up of the detector seen in the raw log() time series is strongly reduced after correction. Top and bottom right: closer look at the regions around the third and fourth warm-ups.