Modulation of Cerebellar Nuclear Activity by Transcranial AC Stimulation in Awake Rats

Transcranial alternating current stimulation of the cerebellum (ctACS) is an emerging neuromodulation technique that can potentially be leveraged to treat neurological disorders and improve learning in healthy individuals. Yet, the effects of ctACS on the neuronal circuits of the cerebellum is elusive. We implanted carbon fiber bundle electrodes in the interpositus nucleus of the cerebellum and an array electrode on the posterior surface of the skull for stimulation in chronic rats. Multi-unit activities (MUA) were recorded from three unanesthetized and quietly resting animals during transcranial application of the current stimuli at various frequencies (10 Hz-300 Hz) and amplitudes as well as after harmaline induced tremors. A frequency-spectrum based method for assessing the modulation strength from the MUA was developed. The results show that the interpositus MUA can be modulated transcranially in a range of frequencies with a peak modulation around 50 Hz. This agrees with an earlier report in general [1] although the peak frequency is lower. This study demonstrates the feasibility of entraining the activity of the cerebellar nuclear cells in awake animals by transcranial application of AC stimulation, as well as the detection of harmaline induced tremor from the MUAs. Future research will be directed towards testing the ctACS effects on this animal model of essential tremor.