High-resolution fMRI detects neuromodulation of individual brainstem nuclei by electrical tongue stimulation in balance-impaired individuals

Abstract

High resolution functional magnetic resonance imaging (fMRI) can be used to precisely identify blood-oxygen-level dependent (BOLD) activation of small structures within the brainstem not accessible with standard fMRI. A previous study identified a region within the pons exhibiting sustained neuromodulation due to electrical tongue stimulation, but was unable to precisely identify the neuronal structure involved. For this study, high-resolution images of neural activity induced by optic flow were acquired in nine healthy controls and nine individuals with balance dysfunction before and after information-free tongue stimulation. Subjects viewed optic flow videos to activate the structures of interest. Sub-millimeter in-plane voxels of structures within the posterior fossa were acquired using a restricted field of view. Whole-brain functional imaging verified that global activation patterns due to optic flow were consistent with previous studies. Optic flow activated the visual association cortices, the vestibular nuclei, and the superior colliculus, as well as multiple regions within the cerebellum. The anterior cingulate cortex showed decreased activity after stimulation, while a region within the pons had increased post-stimulation activity. These observations suggest the pontine region is the trigeminal nucleus and that tongue stimulation interfaces with the balance-processing network within the pons. This high-resolution imaging allows detection of activity within individual brainstem nuclei not possible using standard resolution imaging.

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

“…Finally, the vestibular nuclei, intimately related to the cerebellum and a direct input to the vestibular cortices, also showed modulation by Motion (Bense et al, 2006). This region was found to respond to optic flow using high-resolution imaging of the brainstem (Wildenberg et al, 2011). The grouping of these regions into a single component that responds to optic flow suggests these regions function as a network that works together to process optic flow.…”

Altered Connectivity of the Balance Processing Network After Tongue Stimulation in Balance-Impaired Individuals

“…A high-resolution fMRI study using the same stimulation paradigm and similar subject population presented here suggests that this new response to Motion within the BS is occurring in the trigeminal nuclei, which receive somatosensory afferents from the tongue (Wildenberg et al, 2011a). It is known that there are descending pathways from the superior colliculus to the vestibular nuclei that allow visual-motion information to activate the vestibular complex (Beraneck and Cullen, 2007;Blazquez and Highstein, 2007).…”

“…The sustained effects discovered in those studies hinted that the stimulation may be inducing plasticity within the network that processes stimuli pertinent to maintaining balance. Activation-based fMRI analysis was able to show that this stimulation likely caused sustained modulation of neural processing within the brainstem (BS) (Wildenberg et al, 2011a). The anatomy of the dorsal medulla/pons supports these findings as the trigeminal nuclei, which receive afferents from the tongue, are located adjacent to the vestibular nuclei.…”

“…1). Although defined functionally, it is likely that the BS VOI contains both the vestibular nuclei as well as the trigeminal nuclei-the suspected site of the sustained neuromodulation induced by CN-NINM (Wildenberg et al, 2011a).…”

Ressonância funcional na tontura postural-perceptual persistente

“…O córtex cingulado anterior está envolvido na monitorização e processamento do erro interno, violação de expectativas e resolução de sinais cognitivos discordantes 45 .…”