Abstract
We demonstrate distinct α (7-14 Hz) and β band (15-30 Hz) rhythms in rat somatosensory cortex in vivo using epidural ECoG recordings. Moreover, we show in rats that a genuine ß rhythm coexists alongside ß activity that reflects the first harmonic of the arch-shaped somatosensory α rhythm. This demonstration of a genuine somatosensory ß 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 ß rhythm is distinct from the first harmonic of the arch-shaped α rhythm. The first is based on the rhythms' spatial properties: the α and ß rhythms are demonstrated to have significantly different topographies. The second is based on the rhythms' temporal properties: the lagged phase-phase coupling between the α and ß rhythms is demonstrated to be significantly less than would be expected if both reflected a single underlying non-sinusoidal rhythm. Finally, we demonstrate that a tactile stimulus has the same effect on the somatosensory α and ß rhythms in both rats and humans, namely by suppressing them. Thus, we not only provide evidence for the existence of genuine α and ß rhythms in rat somatosensory cortex, but also for their homology to the primate sensorimotor α and ß rhythms.
