Cortical oxyhemoglobin dynamics during caloric test with near-infrared spectroscopy

To study cerebral cortical function in equilibrium, cortical oxyhemoglobin saturation rate was measured during Caloric test for five volunteers. Near-infrared spectroscopy (NIRS) measuring backscattered reflection is a non-invasive, good method to study human cortical activation. Over both temporal areas, the oxyhemoglobin saturation rate changed during the irrigation to the auricle, the irrigation to the ear meatus, and during nystagmus. Caloric test induced various cortical activation; e.g., the sensation in irrigating iced water, vestibulo-autonomic response, vestibulo-ocular response, anticipation to the stimuli and so on.