Analyses of seasonal variation in size of brain regions in Poland and Germany
To analyze the variation in volume of brain regions between stages of Dehnel’s Phenomenon, locations and sexes we used ANOVA for each brain region separately, with size corrected volume of the brain region as response variable and age, location and sex and their interactions as explanatory variables. Here, we included sex in the model based on the significant effect we had previously found on the seasonal changes of some brain regions in Radolfzell (Lázaro et al. , 2018b). To tease apart the influence of season, geographic difference, and sexual dimorphism, we did pair-wise comparisons between the factors’ levels using Tukey tests for multiple comparisons.
All analyses were performed in R 3.5.0 (R Core Team, 2015).