1 Hz. To calculate LowFq, each 64–200 Hz power time courses was decomposed into Ku-0059436 chemical structure nine 60 s blocks, with 30 s overlap of consecutive blocks. First, the mean time course value was subtracted from each 60 s block. Second, each block was multiplied by a 60 s Hamming window. Third, a 600-point DFFT was computed for each block. Fourth, to compute the modulation spectrum of each block, we averaged the power spectra across all blocks in the first and second presentations of the movie. Finally, using this averaged modulation spectrum, we computed LowFq as the power in the modulation spectrum below 0.1 Hz divided by the total power in the modulation spectrum.

Estimations of LowFq in the fixation data were performed in the same way, but using 20 s data windows with 10 s overlap. The ACW was defined as the full-width-at-half-maximum of the temporal autocorrelation function of the power time course. To calculate ACW, each 64–200 Hz power time courses was decomposed into 20 s blocks with 10 s of overlap. We computed the autocorrelation function, MK-8776 ic50 R  i(τ), of

the power fluctuations of the i-th electrode within each block: Ri(τ)=corr(Pi(t),Pi(t−τ)),Ri(τ)=corr(Pi(t),Pi(t−τ)),and then averaged the Ri(τ) functions across all blocks obtained from all runs within a condition. Finally, the ACW for the i-th electrode was defined as ACWi=2minτR¯i(τ)<12,where R¯i(τ) is the average of all autocorrelation functions Ri(τ) computed within individual blocks for that

electrode. Spectral power was estimated in 1 s windows stepping by 0.1 s, so that τ values increment by 0.1 s and the minimum value of ACW is 0.2 s. The Wiener-Khinchin theorem connects the autocorrelation function most and power spectrum of a time series, and so the LowFq and the ACW parameters are related measures of the dynamical timescale. In the present data the LowFq and ACW parameters are robustly correlated (Figure S2), but we present both measures because they are differently parameterized (LowFq requires a frequency cutoff while the ACW measure requires an autocorrelation cutoff) and they do not always provide the same information. Because of the autocorrelation in the power modulation time courses, the statistical significance of r-values was assessed using a permutation procedure (Efron and Tibshirani, 1993) that preserved the autocorrelation structure of the original data within the surrogate data. Time courses were subdivided into blocks of 20 s length and the blocks were randomly permuted to produce a surrogate time course. For each empirical time course a set of 2,000 surrogate time courses was generated. For every empirical correlation, 2,000 surrogate correlations were computed using the surrogate time courses. p values were assigned to each r-value by comparing the observed correlation against the distribution of correlations under the null model.