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Fransen AM, Dimitriadis G, van Ede F, Maris E. Distinct ␣-and ␤-band rhythms over rat somatosensory cortex with similar properties as in humans. J Neurophysiol 115: 3030 -3044, 2016. First published March 23, 2016 doi:10.1152/jn.00507.2015.-We demonstrate distinct ␣-(7-14 Hz) and ␤-band (15-30 Hz) rhythms in rat somatosensory cortex in vivo using epidural electrocorticography recordings. Moreover, we show in rats that a genuine ␤-rhythm coexists alongside ␤-activity that reflects the second harmonic of the arch-shaped somatosensory ␣-rhythm. This demonstration of a genuine somatosensory ␤-rhythm depends on a novel quantification of neuronal oscillations that is based on their rhythmic nature: lagged coherence. Using lagged coherence, we provide two lines of evidence that this somatosensory ␤-rhythm is distinct from the second harmonic of the archshaped ␣-rhythm. The first is based on the rhythms' spatial properties: the ␣-and ␤-rhythms are demonstrated to have significantly different topographies. The second is based on the rhythms' temporal properties: the lagged phase-phase coupling between the ␣-and ␤-rhythms is demonstrated to be significantly less than would be expected if both reflected a single underlying nonsinusoidal rhythm. Finally, we demonstrate that 1) the lagged coherence spectrum is consistent between signals from rat and human somatosensory cortex; and 2) a tactile stimulus has the same effect on the somatosensory ␣-and ␤-rhythms in both rats and humans, namely suppressing them. Thus we not only provide evidence for the existence of genuine ␣-and ␤-rhythms in rat somatosensory cortex, but also for their homology to the primate sensorimotor ␣-and ␤-rhythms.

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