近赤外線分光法(NIRS)を用いた回転刺激に対する大脳皮質応答の解析

Understanding cortical activity associated with vestibular input is of great importance in the diagnosis and treatment of vertigo. Previous studies on the vestibular cortex in humans have mainly used fMRI and PET, but due to the characteristics of these measuring equipments, it has been difficult to measure the cortical responses to physiological vestibular stimuli, such as rotational acceleration or deceleration to the head. Therefore, we used a portable near-infrared spectroscopy system to measure the cortical blood flow responses to rotational acceleration or deceleration stimuli in 18 right-handed normal subjects while the subjects sat on a rotational chair. The temporoparietal junction (TPJ) of both sides, which is considered as the core region of the so-called “multiple vestibular cortices, ” was selected as the region of interest for the measurement. All subjects accelerated and decelerated at 3°/sec in either direction, and then performed the same acceleration and deceleration in the opposite direction a total of four times. The NIRS-SPM software was used to verify whether the concentration of oxyhemoglobin was significantly increased under the four conditions of rightward rotational acceleration, rightward deceleration, leftward acceleration, and leftward deceleration in the subjects. The results showed that there was predominant activation within the TPJ under all four conditions, that the direction of nystagmus coincided with the laterality of the activated TPJ under all the conditions, and that the pattern of TPJ activation differed depending on whether the left or right semicircular canal was stimulated.