Thank you for you help Doug, of course I can explain it better
Let's suppose that resulting from the ANOVA I get three significative areas (i.e. enthorhinal, parietal and frontal), do i have to make the pair-wise comparisons on the three areas at once?, or can I perform a pair-wise for enthorhinal, a pair-wise for parietal and a third pair-wise analysis for frontal area?

 Gabriel