fig. 2

Priming the occipital cortex with ouabain increased the incidence of photic stimulation-induced CSDs. Each horizontal line represents continuous recording from one mouse primed with 0.1 mM ouabain and then subjected to 1-min on and off cycles of photic stimulation at 8–12 Hz for 10 min except a few that lasted a bit shorter or longer due to interventions needed (e.g. for clearing the airway) or timing errors in stimulator. Stimulation started after at least a 30-min silent period without any CSD. The number of ouabain-induced CSDs prior to starting stimulation is given before each line in parentheses. Stimulation (labeled orange) was stopped when a CSD was triggered (red circles). Green circles depict the occasional CSDs unrelated to stimulation. Bar graph shows that the CSD incidence was significantly higher (*p < 0.001, Chi-square test) during photic stimulation compared to the non-stimulated periods. Only positive experiments are displayed on the left to simplify viewing of the flow charts by omitting the negative experiments (n = 6), but statistical analysis on the right included all animals regardless of the stimulation effectiveness (15 mice) and compared them to 16 non-stimulated mice treated with 0.1 mM ouabain. Because the CSD incidence was very low in controls, it was not suitable for illustration (i.e. 16 lines mostly with no incidences)