Sustained cortical and subcortical neuromodulation induced by electrical tongue stimulation

Abstract

This pilot study aimed to show that information-free stimulation of the tongue can improve behavioral measures and induce sustained neuromodulation of the balance-processing network in individuals with balance dysfunction. Twelve balance-impaired subjects received one week of cranial nerve non-invasive neuromodulation (CN-NINM). Before and after the week of stimulation, postural sway and fMRI activation were measured to monitor susceptibility to optic flow. Nine normal controls also underwent the postural sway and fMRI tests but did not receive CN-NINM. Results showed that before CN-NINM balance-impaired subjects swayed more than normal controls as expected (p≤0.05), and that overall sway and susceptibility to optic flow decreased after CN-NINM (p≤0.005 & p≤0.05). fMRI showed upregulation of visual sensitivity to optic flow in balance-impaired subjects that decreased after CN-NINM. A region of interest analysis indicated that CN-NINM may induce neuromodulation by increasing activity within the dorsal pons (p≤0.01).

Electrical Tongue Stimulation Normalizes Activity Within the Motion-Sensitive Brain Network in Balance-Impaired Subjects as Revealed by Group Independent Component Analysis

“…For additional demographic details please see the work of Wildenberg et al (2010). Balance-impaired subjects were recruited primarily through referral from clinicians aware of ongoing studies within our research group.…”

“…Additionally, rotation about the center of the viewfield was produced using the superposition of two sinusoids (0.2 and 0.35 Hz) to prevent prediction of the motion. These stimuli were identical to those described in our previous study (Wildenberg et al, 2010). Both stimuli had a total image size of 800 · 600 pixels (equal to the resolution of the display goggles) and the dynamic video was displayed at 60 frames-per-second.…”

“…Owing to the overlap of these networks, damage can also result in upregulated sensitivity to motion within the visual field that mimics or implies ego-motion (Dieterich, 2007;Mergner et al, 2005;Redfern and Furman, 1994). Previous work has suggested that individuals with central and/or peripheral balance disorders have increased neural activity within V5/ hMT + , an association cortex involved in motion perception, compared with healthy controls when viewing optic flow Wildenberg et al, 2010). If understood as a network, it is likely that this neural upregulation is not limited to V5/hMT + .…”

“…Our recent work investigated the effects of informationfree stimulation of the tongue, termed Cranial Nerve NonInvasive Neuromodulation (CN-NINM), on the processing of optic flow by individuals with balance disorders (Wildenberg et al, 2010). This study demonstrated that CN-NINM can produce sustained improvements in postural responses and modulate activity within some structures of the balance-processing network.…”

“…It is reasonable to expect that for stimulation of the brainstem to produce sustained changes in cortical processing of optic flow, activity of the entire network must be modulated. To characterize the upregulation and downregulation of brain networks due to CN-NINM, we used group ICA to reanalyze the fMRI data collected in that previous study (Wildenberg et al, 2010). This report presents the results of this analysis technique and its potential for studying the entire balance-processing network and how it functions as a unit.…”