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Left caloric vestibular stimulation ameliorates right hemianesthesia
G Bottini1, E Paulesu, M Gandola
1Psychology Department, University of Pavia, 27100 Pavia, Italy. g.bottini@unipv.it
Neurology
|October 26, 2005
Summary
Left caloric vestibular stimulation (CVS) can temporarily relieve hemianesthesia in both left and right brain-damaged patients. This occurs because CVS influences the hemisphere better equipped to process full-body sensory information, suggesting brain asymmetry in hand representation.
Area of Science:
- Neuroscience
- Vestibular System
- Somatosensory Processing
Background:
- Left caloric vestibular stimulation (CVS) temporarily improves left hemianesthesia in right-brain-damaged patients.
- However, right CVS does not improve right hemianesthesia in left-brain-damaged patients, a discrepancy needing explanation.
Purpose of the Study:
- To investigate the effect of CVS on hemianesthesia in both left- and right-brain-damaged patients.
- To explore the neural mechanisms underlying CVS effects using functional magnetic resonance imaging (fMRI).
Main Methods:
- Assessed hemianesthesia in patients with left and right brain damage.
- Conducted fMRI during tactile stimulation before and after left CVS in a left-brain-damaged patient.
- Performed fMRI touch studies in unimpaired subjects without CVS.
Main Results:
- Left CVS transiently resolved right hemianesthesia in a left-brain-damaged patient.
- fMRI revealed left CVS modulated the secondary somatosensory area (SII) response to tactile stimuli in the right hemisphere.
- In unimpaired subjects, the right SII showed stronger activation for ipsilateral stimuli compared to the left SII for contralateral stimuli.
Conclusions:
- Left CVS effectively treats both left and right hemianesthesia by modulating the hemisphere with broader somatosensory representation.
- Results indicate a hardwired hemispheric asymmetry in hand representation originating in somatotopically organized regions like SII.