Fig. 2.

Background noise as a function of number of trials for both subject groups. a Frequency spectrum for PD and Ctrl, computed using one to the maximum amount of trials in the blank-screen (baseline) condition of 0% foreground and 0% surround contrast. b Amplitude at the 25 Hz bin as a function of number of trials. A fast Fourier transform (FFT) was computed on the average time-domain signals across the given number of trials first, with that number selected randomly 1000 times from the total trials available for that condition, and the resulting FFTs averaged. Background noise levels matched when the FFT was computed on the average signal across the maximum available trials (up to eight per subject) for PD subjects and half of the total (up to four trials per subject) for control subjects