Attenuated ACC power in chronic tic disorder. During incongruent trials, subjects with chronic tic disorder (CTD) showed broadband attenuation in spectral power in the anterior cingulate cortex. Time-frequency ranges of significant between-group differences are marked by boxes for theta (θ, 4–7 Hz), alpha (α, 8–12 Hz), and low (13–20 Hz) and high beta (β, 20–30 Hz) frequency bands.