A better oscillation detection method robustly extracts EEG rhythms across brain state changes: The human alpha rhythm as a test case

Oscillatory activity is a principal mode of operation in the brain. Despite an intense resurgence of interest in the mechanisms and functions of brain rhythms, methods for the detection and analysis of oscillatory activity in neurophysiological recordings are still highly variable across studies. We recently proposed a method for detecting oscillatory activity from time series data, which we call the BOSC (Better OSCillation detection) method. This method produces systematic, objective, and consistent results across frequencies, brain regions and tasks. It does so by modeling the functional form of the background spectrum by fitting the empirically observed spectrum at the recording site. This minimizes bias in oscillation detection across frequency, region and task. Here we show that the method is also robust to dramatic changes in state that are known to influence the shape of the power spectrum, namely, the presence versus absence of the alpha rhythm, and can be applied to independent components, which are thought to reflect underlying sources, in addition to individual raw signals. This suggests that the BOSC method is an effective tool for measuring changes in rhythmic activity in the more common research scenario wherein state is unknown.

Research highlights►BOSC is a method to identify oscillatory activity in time series data. ►BOSC sets a power and a duration threshold to exclude non-rhythmic epochs. ►The power threshold is derived from an estimate of the background spectrum. ►The duration threshold is based on the desired number of cycles at each frequency. ►In this study BOSC reliably extracts the human occipital alpha oscillation.