P297 Sensory plasticity changes induced by somatosensory and cerebellar tDCS in alert mice

Abstract

Introduction During the past years, new evidence has revealed the importance of the cerebellar-brain-inhibition (CBI) pathway on cognitive and sensory processing. The modulation of the cerebellar cortex through non-invasive stimulation techniques, as transcranial direct-current stimulation (tDCS), could contribute to the better understanding of neuronal mechanisms underlying the implication of cerebellar cortex in these processes. Objectives The aim of this study was to explore cerebro-cerebellar interactions affecting long-term plasticity in the somatosensory (SS) cortex by modulating cerebral and cerebellar cortical excitability in behaving mice. Materials and methods Mice were prepared for the chronic recording of local field potentials (LFPs) in the SS cortex in response to electrical whisker pad stimulation, as well as for simultaneous tDCS. Animals received tDCS over the cerebellum or the SS cortex at different current intensities with a duration of 5 s to asses immediate effects, and during 20 min to address after-effects on SS-LFPs. tDCS effects on long-term plasticity processes in the SS cortex were determined by using two conditioning protocols consisting of 8 and 50 Hz whisker stimulation with a duration of 10 min and 96 s, respectively. Each protocol was combined with the simultaneous presentation of tDCS or sham condition. Results Anodal increased and cathodal decreased in an immediate way the amplitude of SS-LFPs when applied to the ipsilateral SS cortex, whereas the opposite effects were obtained when tDCS was presented to the contralateral cerebellar cortex. Concerning long-term after-effects, cathodal tDCS over the SS cortex induced a long-term depression of LFPs whereas no effects were observed after anodal currents. Long-term potentiation of SS-LFPs was evoked by both cathodal and anodal cerebellar tDCS. Finally and as expected, long-term depression and long-term potentiation of SS-LFPs induced by 8 and 50 Hz whisker stimulation were modulated by simultaneous cerebellar tDCS. Conclusions The results demonstrate the capability of tDCS to modulate the excitability of SS and cerebellar cortices, as well as the potential role of the cerebellar cortex in the control of plastic changes occurring in the sensory cortex of behaving animals.