Using a wavelet time frequency analysis is what they generally do to highlight these kinds of patterns when dealing with brain activations of neural populations. It gives you an idea of power of a specific frequency over time [e.g., http://www.lauriefrick.com/wp-content/uploads/2011/07/wavlet...]. And apparently it's already been used for analogous purposes: [ http://www.paramics-online.com/downloads/technicaldocs/wavel...] :-)