Hypothesis 3 was tested as follows:
Light effect on membrane current was calculated on the median trace of the 15 recorded traces. For each of the 50 light pulses, the effect of light on membrane current was calculated as the difference between the average membrane current in the 1 s preceding the beginning of patterned light (the CTR period) and the average membrane current during the light period. For each of the three powers used, this resulted in the median light effect for each of the 50 pulses (i.e., effect of the 1st light pulse; ……..; effect of the 50th light pulse). The values calculated for all recorded neurons were used for descriptive statistics by calculating the average population effect ± 95% CI as well as the Cohen’s d ES (average of population effect /STD of population effect). Similar analyses were performed for the positive control (Test LED) and the total continuous illumination (T.I. LED), for which the effect was evaluated as the difference between the average membrane current during light stimulation and the average membrane current in the respective CTR period. Statistical test was performed only for three light pulses (the 1st, 25th, and 50th) by using a unilateral one-sample Wilcoxon signed rank test (tested hypothesis, median effect >0). The σ risk was set at 0.05 and a Bonferroni-Holm correction was applied. The experiment weas conducted on 24 neurons for each pattern of light stimulation and cell type (240 neurons in total). This sample size was determined based on a previously published experiment showing an effect size (ES) of continuous light stimulation on MC membrane current equal to 1 (Ait Ouares et al. , 2019) and takes in account the Bonferroni-Holm correction for 30 statistical comparisons. Therefore, the statistical power to observe an effect as small as that produced by 1 s continuous light stimulation is between 91% et 99%, depending on the level of correction (calculated with G*Power 3.1.9.2). The 24 MCs were recorded from 51 different mice (i.e., different patterns were applied on slices coming from the same animal). The homogeneity between the groups produced by the “Test LED” was assessed by a one-way Kruskal-Wallis test.