Altered dynamics of visual contextual interactions in Parkinson’s disease

Background frequency spectrum profiles in patients versus controls. Fast Fourier transforms were computed on the last 2240？ms of all trials with 0% foreground and 0% surround contrast (blank screen, shown in inset) and then averaged across trials and across subjects within each group. Patients showed significantly higher spectral amplitudes, marked with asterisks for each of the corresponding frequency bins (bootstrapping test, p？<？0.05). Shaded error bars indicate mean？±？standard error of the mean (s.e.m.