On the Cerebral and Cerebellar Cortical Activities in the Rat

25 Cerebellum is a highly organized structure with a crystalline morphology that has always intrigued 26 neuroscientists. Much of the cerebellar research has been conducted in anesthetized animals, 27 particularly using ketamine/xylazine combination in rats. It is not clear how and to what extent the 28 cerebellar cortical circuitry is affected by this anesthesia. In this study, we recorded spontaneous and 29 evoked potentials from the cerebellar surface with chronically implanted, flexible-substrate, multi30 electrode arrays (MEA) in rats and compared them to the signals simultaneously recorded from the 31 motor cortex with similar electrodes. The power spectra and the inter-contact coherence plots of the 32 spontaneous activity in the awake-quiet animals extended up to 800Hz in the cerebellum and only up to 33 200Hz in the motor cortex. Ketamine/xylazine anesthesia suppressed most of the activity in the 34 cerebellar cortex, which was in clear contrast to the motor cortex. In the awake cerebellum, large 35 coherence values were observed between contact pairs as far apart as ~2mm. Otherwise, there was not 36 a discernable relation between the coherence and the inter-contact distance. These results suggest that 37 the surface electrodes can provide much more detailed information about the state of neural circuits 38 when they are used on the cerebellar cortex as compared to the cerebral areas. This may be due to the 39 proximity of the molecular layer cells to the pial surface in the cerebellum. 40