Conrad Julian, Boegle Rainer, Ertl Matthias, Brandt Thomas, Dieterich Marianne
Department of Neurology, Ludwig-Maximilians-Universität, Munich, Germany.
German Center for Vertigo and Balance Disorders - IFBLMU (DSGZ), Ludwig-Maximilians-Universität, Munich, Germany.
Front Neurol. 2018 Mar 2;9:112. doi: 10.3389/fneur.2018.00112. eCollection 2018.
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.
前庭信号参与诸如空间定向及其障碍等更高层次的皮质功能。例如，前庭功能障碍会导致空间忽视，而热刺激可使其暂时改善。前庭和视觉系统在忽视恢复过程中的确切作用和机制尚不清楚。
在一名患有半侧空间忽视的患者中，于急性期中以及右侧大脑中动脉梗死6个月后恢复时，在热前庭刺激前后记录静息态功能连接（fc）磁共振成像。分析时使用前庭[顶叶岛盖（OP2）]、顶叶[后顶叶皮质（PPC）；7A，hIP3]和视觉皮质（VC）中的种子点。
在热刺激后的急性期，右侧OP2与左侧OP2、前扣带回以及海马旁/海马之间的fc双侧增加（即前庭网络），而VC中同源区域之间的半球间fc降低。6个月后，未进行刺激时在前庭网络中也发现了类似的fc增加。此外，还观察到OP2与PPC和VC之间的fc增加；在半球间，两个PPC以及右侧PPC与两个VC之间均如此。
急性期热刺激后忽视的改善与双侧前庭皮质区域与海马旁和背侧前扣带回之间的fc增加有关，但同时与半球间VC连接性降低有关。这揭示了与忽视的长期恢复相比，在空间定向改善方面某种程度上相似但又不同的短期机制（前庭刺激）。
