Group averages of absolute power maps. A: normal subjects (n=22). B: patients with multiple sclerosis who underwent cognitive tests (n=21). C: cognitively unimpaired multiple sclerosis (n=12). D: cognitively impaired multiple sclerosis (n=9). E-F: p values (Student's t test). E: group B v group A. F: group D v group A. Red shades in E-F represent a significant power increase in groups B and D.