Cortical Neuromodulation Modifies Cerebral Vasomotor Reactivity

Abstract

Background and Purpose-Cerebral vasomotor reactivity (VMR) is a capability of cerebral vessels to dilate in response to hypercapnia. Transcranial direct current stimulation (tDCS) effects on cerebral hemodynamics have been poorly studied. Methods and Results-Ten healthy subjects underwent anodal/cathodal tDCS on the left motor cortex. Before and after tDCS, VMR assessment by transcranial Doppler and an electrocardiogram were performed. Normalized low-frequency band power of heart rate variability and its reactivity from basal to VMR condition (LFN react ) were estimated as relative markers of sympathetic activation. tDCS exerted a polarity-specific effect on both VMR (Pϭ0.0001) and LFN react (Pϭ0.001). Anodal tDCS decreased VMR by 3.4%/mm Hg CO 2 bilaterally and increased LFN react , whereas cathodal tDCS increased VMR by 0.8%/mm Hg CO 2 bilaterally and reduced LFN react . Conclusions-Cerebral VMR is modified by tDCS. Based on the consensual changes with heart rate variability, we can hypothesize that the sympathetic nervous system could modulate the bihemispheric modification of VMR. Further studies are needed to confirm this hypothesis.

Non-invasive brain stimulation and the autonomic nervous system

“…As expected, due to the intrinsic characteristics of tDCS, most of these studies used sham stimulation (76.9%) and measured autonomic function 1 min away from stimulation. Most of the positive ANS effects were attributed to anodal stimulation, but in two articles, cathodal stimulation induced significant autonomic modifications in both DLPFC (Beeli et al, 2008) and M1 (Vernieri et al, 2010) spots. The most frequently used autonomic tests can be seen in Fig.…”

“…Other techniques such as QSART and microneurography, although very accurate means of assessing sympathetic function, are unable to detect preganglionic dysfunction and do not provide information on the parasympathetic branch of the ANS (Illigens and Gibbons, 2009). Finally, it is important to underscore that, although CVR provides consistent data on NIBS studies (Vernieri et al, 2009(Vernieri et al, , 2010, there is still no standardization of the technique and, therefore, its use cannot be recommended systematically. Finally, the use of brain derived neurotrophic factor measurement (BDNF) has been linked to plastic effects in anesthetized animals (Gersner et al, 2011) and also might help to select specific forms or neurostimulation depending on BDFN polymorphism i.e., variants Val/Met (Jayasekeran et al, 2011;Cirillo et al, 2012).…”

Nonlinear effects of respiration on the crosstalk between cardiovascular and cerebrovascular control systems

“…both anode and cathode are placed on the scalp) targeting M1 and DLPFC, but autonomic function was also tested with tDCS delivered on temporal regions [145]. Whenever documented, positive autonomic effects of tDCS were related to anodal stimulation, with only two studies supporting effects for cathodal tDCS delivered on the DLPFC [146] or on M1, the latter addressing vasomotor reactivity changes [147]. However, only two studies were designed ad hoc to investigate the effect of tDCS on brainstem structures through a unipolar scalp montage linked with an extracephalic (arm/shoulder) electrode positioning: both studies, one targeting M1 [148] and the other one targeting the frontal midline [144], suggest null or mild effects on cardiovascular and respiratory functions, with a progressive shift over time in favour of the sympathetic tone, a finding that however was present during sham (i.e.…”

Hyperventilation induces sympathetic overactivation in mesial temporal epilepsy

“…In particular, during a standard EEG recording, HV increased the ratio between LF and HF band power, which is considered as a reliable ECG-derived index of sympathetic activation (Vernieri et al, 2010). These results provide new hints on the physiological pathways mediating seizure susceptibility to HV in MTLE patients.…”