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Cortical correlates of vestibulo-ocular reflex modulation: a PET study
Yasushi Naito1, Ichiro Tateya, Shigeru Hirano
1M.D. Department of Otolaryngology - Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan. naito@ent.kuhp.kyoto-u.ac.jp
Brain : a Journal of Neurology
|June 14, 2003
Summary
This study used PET scans to map brain activity during vestibular reflex modulation. Findings reveal specific cortical regions involved in visual suppression and habituation of the vestibulo-ocular reflex (VOR).
Area of Science:
- Neuroscience
- Vestibular System Research
- Neuroimaging
Background:
- The vestibulo-ocular reflex (VOR) stabilizes gaze during head movements.
- Understanding the cortical processing of VOR modulation is crucial for diagnosing and treating vestibular disorders.
Purpose of the Study:
- To elucidate the cortical correlates of vestibulo-ocular reflex (VOR) modulation.
- To investigate brain activation patterns during visual fixation suppression and habituation of caloric vestibular nystagmus.
Main Methods:
- Positron Emission Tomography (PET) was used to measure regional cerebral blood flow (rCBF).
- 12 healthy subjects underwent caloric vestibular stimulation with and without visual fixation, and repeated stimulation for habituation.
- Correlations between rCBF and nystagmus parameters (slow phase eye velocity, suppression, habituation) were analyzed.
Main Results:
- Positive correlation between rCBF and nystagmus velocity was observed in the insula, inferior parietal lobule, and visual cortex.
- Visual fixation suppression showed co-activation in frontal eye fields, temporal pole, and visual cortex, with deactivation in vestibular cortices.
- Habituation led to activation in the cingulate and parietal cortices, and deactivation in the insula and visual cortex.
- The cuneus showed co-activation in both suppression and habituation, while the anterior insula, cingulate, and inferior parietal lobule showed co-deactivation.
Conclusions:
- The parieto-insular cortex and inferior parietal lobule are key in vestibular processing, with lateralization dependent on nystagmus direction.
- Inhibitory visual-vestibular interaction in the cortex is supported by deactivation of vestibular cortices during visual fixation.
- Vestibular habituation involves activation of cingulate, parietal, and visual cortices, and cerebellar regions.
- Visual suppression and habituation of VOR may share overlapping cortical and subcortical mechanisms.