title: Effects of cerebellar transcranial alternating current stimulation on motor cortex excitability and motor function.
abstract: The cerebellum regulates several motor functions through two main mechanisms, the cerebellum-brain inhibition (CBI) and the motor surround inhibition (MSI). Although the exact cerebellar structures and functions involved in such processes are partially known, Purkinje cells (PC) and their surrounding interneuronal networks may play a pivotal role concerning CBI and MSI. Cerebellar transcranial alternating current stimulation (tACS) has been proven to shape specific cerebellar components in a feasible, safe, effective, and non-invasive manner. The aim of our study was to characterize the cerebellar structures and functions subtending CBI and MSI using a tACS approach. Fifteen healthy individuals underwent a cerebellar tACS protocol at 10, 50, and 300 Hz, or a sham-tACS over the right cerebellar hemisphere. We measured the tACS aftereffects on motor-evoked potential (MEP) amplitude, CBI induced by tACS (tiCBI) at different frequencies, MSI, and hand motor task performance. None of the participants had any side effect related to tACS. After 50-Hz tACS, we observed a clear tiCBI-50Hz weakening (about +30%, p < 0.001) paralleled by a MEP amplitude increase (about +30%, p = 0.001) and a reduction of the time required to complete some motor task (about -20%, p = 0.01), lasting up to 30 min. The 300-Hz tACS induced a selective, specific tiCBI-300Hz and tiCBI-50Hz modulation in surrounding muscles (about -15%, p = 0.01) and MSI potentiation (about +40%, p < 0.001). The 10-Hz tACS and the sham-tACS were ineffective (p > 0.6). Our preliminary data suggest that PC may represent the last mediator of tiCBI and that the surrounding interneuronal network may have an important role in updating MSI, tiCBI, and M1 excitability during tonic muscle contraction, by acting onto the PC. The knowledge of these neurophysiological issues offers new cues to design innovative, non-invasive neuromodulation protocols to shape cerebellar-cerebral functions.
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Naro
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Bramanti
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Leo
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Manuli
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Sciarrone
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Russo
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy.
authors.forename: Placido
authors.initials: P
authors.lastname: Bramanti
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo", Via Palermo, Contrada Casazza, S.S. 113, 98124, Messina, Italy. salbro77@tiscali.it.
authors.forename: Rocco Salvatore
authors.initials: RS
authors.lastname: Calabrò
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D000071080:Cortical Excitability; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D009433:Neural Inhibition; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D034941:Upper Extremity / Q000294:innervation*
keywords: Cerebellar brain inhibition (CBI); Cerebellum; Muscle surround inhibition (MSI); Tonic activation; Transcranial alternating current stimulation (tACS); Transcranial magnetic stimulation (TMS)