Distinct α- and β-band rhythms over rat somatosensory cortex with similar properties as in humans

We demonstrate distinct alpha-(7-14 Hz) and beta-hand (15-30 Hz) rhythms in rat somatosensory cortex in vivo using epidural electrocorticography recordings. Moreover, we show in rats that a genuine beta-rhythm coexists alongside beta-activity that reflects the second harmonic of the arch-shaped somatosensory a-rhythm. 'this demonstration of a genuine somatosensory beta-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 beta-rhythm is distinct from the second harmonic of the arch shaped alpha-rhythm. The first is based on the rhythms' spatial properties: the alpha-and beta-rhythms are demonstrated to have significantly-different topographies. The second is based on the rhythms' temporal properties: the lagged phase-phase coupling between the alpha-and beta-rhythms is demonstrated to he 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 alpha-and beta-rhythms in both rats and humans, namely suppressing them. Titus we not only provide evidence for the existence of genuine alpha-and beta-rhythms in rat somatosensory cortex, but also for their homology to the primate sensorimotor alpha-and beta-rhythms.