Transcranial direct current stimulation and cerebral vasomotor reserve: a study in healthy subjects

BACKGROUND AND PURPOSECerebral vasomotor reserve (VMR) is the capability of cerebral arterioles to change their diameter in response to various stimuli, such hypercapnia. Changes of VMR due to transcranial direct current stimulation (tDCS) have been poorly studied. METHODSTwenty-five healthy subjects underwent anodal/cathodal and sham tDCS on right primary motor area. Before and after tDCS, we assessed VMR by Transcranial Color-Coded Sonography (TCCS) calculating trought Breath Holding Index (BHI) and Heart Rate Variability (HRV), in particular after Valsalva manouver. RESULTSA-tDCS decreased VMR and BHI (p < 0.05), whereas C-tDCS increased VMR, and BHI (p < 0.05); Sham doesn't provide statistically significant of both VMR, BHI and HRV (p > 0.05). CONCLUSIONSOur study confirms that tDCS induces a modification of bilateral VMR with a polarity-specific effect; based on this bilateral MFV and BHI modifications, we can speculate an involvement of the SNS in the VMR regulation.