Effect of Current Source Density (CSD)-transforming on peak alpha frequency
We extracted peak alpha frequencies from the dataset both after applying CSD-transformation during EEG pre-processing and without applying CSD-transformation (see Methods). For resting state data, the two versions of the dataset were highly correlated (r = 0.96, P < 0.001) and the mean difference between the two was 0.07 Hz (t = 1.9, P > 0.05). Pre-stimulus CSD transformed data was also highly correlated with its non-CSD transformed counterpart (r = 0.62, P < 0.001). The mean difference between these versions was 0.27 Hz. Though the two datasets did not differ from each other significantly (t = 1.96, P > 0.05), a difference of 0.27 Hz in the alpha band range could potentially be meaningful. We therefore conducted all further correlation tests with both the CSD transformed and the non-CSD transformed versions of the data. Unless otherwise stated, we found no difference between the two versions of the data and only reported results from the non-CSD transformed dataset.