Fig. 1: Alpha rhythms are generated in visual neocortex after transient periods of cellular and network excitation.

a Alpha rhythms manifest following glutamate-induced gamma rhythms in slices of V1 under cholinergic (10 μM carbachol) neuromodulation. Upper example trace shows 60 s of L4 LFP with glutamate ejected at the time of the arrow. Graph shows an example colormapped spectrogram of the resulting pattern of rhythm generation. Note the initial generation of dual (high- and low-) gamma rhythms, which rapidly transition to a single alpha rhythm at ca. 20 s. Lower example traces show examples from the 2 time points as indicated in the spectrogram. Scale bars upper trace, 100 μV, 6 s; lower traces, 100 μV, 200 ms. b A pharmacological model, based on the findings in a produced a more ‘persistent’ alpha rhythm lasting over 160 min. Upper trace shows a 30 s example of alpha rhythms generated pharmacologically. Graph shows example spectra in three experimental conditions: Bath application of kainate alone in the initial, excitatory stage of the model (black) generating dual-gamma spectral peaks; bath application of NBQX and DK-AH269 to generate a robust alpha rhythm (red); bath application of NBQX alone to reduce AMPA receptor-mediated excitation (blue). Lower example traces show examples in each of these three conditions. Scale bars upper trace 100 μV, 3 s, lower traces, 100 μV, 200 ms.