Thalamic infarctions cause side-specific suppression of vestibular cortex activations

Area of Science:

• Neuroscience
• Vestibular System Research
• Neuroimaging

Background:

• The posterolateral thalamus relays ascending vestibular information to multisensory vestibular cortex areas.
• Unilateral thalamic lesions can disrupt thalamo-cortical projections and hemispheric interactions.
• Understanding these disruptions is key to understanding vestibular processing and its cortical representation.

Purpose of the Study:

• To investigate the effects of unilateral posterolateral thalamic lesions on vestibular cortex activation.
• To evaluate the impact on right hemispheric dominance and visual-vestibular interactions.
• To explore perceptual and ocular motor consequences during caloric vestibular stimulation.

Main Methods:

• H2O15-PET imaging during caloric vestibular stimulation of the external ears.
• Study included eight right-handed patients with acute unilateral thalamic infarctions/hemorrhages (four right, four left).
• Group analyses compared activation patterns between patients with right-sided and left-sided lesions.

Main Results:

• Activation of the multisensory vestibular cortex was significantly reduced in the hemisphere ipsilateral to the thalamic lesion.
• Reduced activation was also observed in the hemisphere contralateral to the stimulated ipsilesional ear.
• Right hemispheric dominance was preserved in right-handers, irrespective of lesion side; visual-vestibular interaction appeared impaired.

Conclusions:

• The posterolateral thalamus is functionally critical as a relay for vestibular input to the cortex.
• The right hemisphere exhibits dominance in right-handers, even with unilateral thalamic lesions.
• Ascending vestibular pathways, including ipsilateral projections to the inferior insula, bypass the thalamus.