Recovery from Spatial Neglect with Intra- and Transhemispheric Functional Connectivity Changes in Vestibular and Visual Cortex Areas-A Case Study.

Julian Conrad,Thomas Brandt,Matthias Ertl,Marianne Dieterich,Rainer Boegle

doi:10.3389/fneur.2018.00112

Abstract

Vestibular signals are involved in higher cortical functions like spatial orientation and its disorders. Vestibular dysfunction contributes, for example, to spatial neglect which can be transiently improved by caloric stimulation. The exact roles and mechanisms of the vestibular and visual systems for the recovery of neglect are not yet known. Resting-state functional connectivity (fc) magnetic resonance imaging was recorded in a patient with hemispatial neglect during the acute phase and after recovery 6 months later following a right middle cerebral artery infarction before and after caloric vestibular stimulation. Seeds in the vestibular [parietal operculum (OP2)], the parietal [posterior parietal cortex (PPC); 7A, hIP3], and the visual cortex (VC) were used for the analysis. During the acute stage after caloric stimulation the fc of the right OP2 to the left OP2, the anterior cingulum, and the para/hippocampus was increased bilaterally (i.e., the vestibular network), while the interhemispheric fc was reduced between homologous regions in the VC. After 6 months, similar fc increases in the vestibular network were found without stimulation. In addition, fc increases of the OP2 to the PPC and the VC were seen; interhemispherically this was true for both PPCs and for the right PPC to both VCs. Improvement of neglect after caloric stimulation in the acute phase was associated with increased fc of vestibular cortex areas in both hemispheres to the para-hippocampus and the dorsal anterior cingulum, but simultaneously with reduced interhemispheric VC connectivity. This disclosed a, to some extent, similar but also distinct short-term mechanism (vestibular stimulation) of an improvement of spatial orientation compared to the long-term recovery of neglect.

Highlights

The vestibular system subserves eye, head, and body coordination in space, postural control, and the perception of verticality and self-motion [1]
parietal operculum 2 (OP2) R Caloric irrigation during the acute phase led to increased fc in a network that included the parieto-temporo-insular region in both hemispheres, including on the left side the posterior insula, the parietal opercular cortex extending to the superior [superior temporal gyrus (STG)], and the middle temporal gyrus [−36, −31, 19]
While the interhemispheric connectivity between vestibular areas was increased, we found that the interhemispheric connectivity between homologous regions of the VC was reduced after caloric irrigation in the acute phase

Summary

Introduction

The vestibular system subserves eye, head, and body coordination in space, postural control, and the perception of verticality and self-motion [1]. In contrast to other sensory modalities, cortical vestibular areas are multisensory; they closely interact with visual and somatosensory input. Spatial neglect is a heterogeneous disorder of spatial and nonspatial attention which leads to reduced awareness of stimuli in the contralesional hemispace [3, 4]. It can affect the representation of one’s own body, the surroundings, or abstract space, such as imagined space, time lines, and number space [3]. Imaging evidence suggests that spatial neglect should be regarded as a network disorder of spatial and non-spatial attentional systems [5, 6]

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