EEG topography of response to visual stimuli in generalized anxiety disorder.

EEG activity was recorded in 11 normal subjects and 19 patients with generalized anxiety disorder (GAD) at rest and while they were viewing a series of ten 4 sec continuous lights. Topographical cortical changes were assessed using 32-channel EEG power estimate maps. The percent changes from baseline to stimulation, for the first 5 and the last 5 light stimuli, were calculated and topographically mapped. Patients with GAD showed less decrease in alpha activity during the first 5 stimuli and more alpha activity during the last 5 stimuli in comparison to normal controls. Delta, theta, alpha, beta I and beta II did not show any difference during the resting periods. The topographical distribution of response to light was different in each group. Normal controls had a parieto-occipital reactivity and GAD patients a centro-parietal one with the maximum difference between the two groups being located in the occipital region. During the stimulation, beta I activity was decreased in controls and increased in patients. The diminishing reactivity of the patients is interpreted as a diminution of attention to external stimulation because of competing internal interferences. The pattern of regional reactivity suggests the importance of the centro-parietal and/or occipital regions in anxiety.