tDCS Reduces False Memories Figure 1. Schematic representation of electrode montages. A represents bilateral stimulation (35 cm2 electrodes in the left and right ATL) and B represents unilateral stimulation (35 cm2 electrode in the left and 100 cm2 electrode in the right ATL). doi:10.1371/journal.pone.0004959.g001 text as during stimulation). Stimulation was then terminated at the end of the false memory task and the subjects were tested again with the same memory paradigm (referred in the text as after stimulation). Statistical analysis Analyses were performed using Stata statistical software (version 9.2, StataCorp, College Station, Texas). We treated the number of responses as a continuous variable. We therefore analyzed the data using a mixed ANOVA model where the dependent variable was the number of false memories and the independent variables were the condition of stimulation (sham, bilateral and unilateral stimulation) and time course (during or post stimulation). Finally we included the subject ID as a random independent variable to control for the within subject variability. If appropriate, pairwise comparisons were conducted correcting for multiple comparisons using Bonferroni correction. Statistical significance refers to a two- tailed p value ,0.05. Results Participants tolerated stimulation well. When analyzing the number of lures as the dependent outcome, the mixed ANOVA revealed no significant interaction effect between condition and time course (F(2,54) = 0.78, p = 0.46). However, there was a significant effect of condition ((F(2,54) = 18.11, p,0.0001), dem- onstrating that the number of lures was different according to the condition of stimulation. Finally there was no significant effect of time course (F(1,54) = 0.03, p = 0.86); showing that the effects of stimulation were the same during and after stimulation. As the main effect of condition was significant, we then performed pairwise comparisons to compare the different conditions of stimulation (unilateral, bilateral and sham stimula- tion). Both active conditions were associated with a significant decrease in the number of false memories as compared to sham stimulation (by 73.1%, p,0.0001; by 46.3%, p = 0.0006, bilateral and unilateral stimulation, respectively, corrected p-values). Although, it seems that bilateral stimulation induced larger effects, there was only a trend for a significant difference between these two conditions (p = 0.09) (figure 2). Finally, in order to assess whether the reduction in false memories was associated with a reduction of veridical memories (suggesting a failure in memory overall), we performed the same model; but at this time using the veridical memories as the dependent variable. There was no significant effect for the interaction term, the main effect of condition or the main effect of time (F,1 for all the comparisons). Table 1 presents mean+SE for veridical memories during and after each type of stimulation). This confirms that the reduction in false memories was not because subjects had an overall poor memory performance during active stimulation. PLoS ONE | www.plosone.org 3 March 2009 | Volume 4 | Issue 3 | e4959