Department of Biomedical Engineering, National Cerebral & Cardiovascular Center Research Institute, Suita, Osaka, Japan.
J Appl Physiol (1985). 2012 Apr;112(7):1215-22. doi: 10.1152/japplphysiol.00867.2011. Epub 2012 Jan 26.
The present study aims to validate the applicability of infrared (IR) thermal imaging for the study of brain function through experiments on the rat barrel cortex. Regional changes in neural activity within the brain produce alterations in local thermal equilibrium via increases in metabolic activity and blood flow. We studied the relationship between temperature change and neural activity in anesthetized rats using IR imaging to visualize stimulus-induced changes in the somatosensory cortex of the brain. Sensory stimulation of the vibrissae (whiskers) was given for 10 s using an oscillating whisker vibrator (5-mm deflection at 10, 5, and 1 Hz). The brain temperature in the observational region continued to increase significantly with whisker stimulation. The mean peak recorded temperature changes were 0.048 ± 0.028, 0.054 ± 0.036, and 0.097 ± 0.015°C at 10, 5, and 1 Hz, respectively. We also observed that the temperature increase occurred in a focal spot, radiating to encompass a larger region within the contralateral barrel cortex region during single-whisker stimulation. Whisker stimulation also produced ipsilateral cortex temperature increases, which were localized in the same region as the pial arterioles. Temperature increase in the barrel cortex was also observed in rats treated with a calcium channel blocker (nimodipine), which acts to suppress the hemodynamic response to neural activity. Thus the location and area of temperature increase were found to change in accordance with the region of neural activation. These results indicate that IR thermal imaging is viable as a functional quantitative neuroimaging technique.
本研究旨在通过对大鼠皮层桶状核的实验验证红外（IR）热成像在研究大脑功能中的适用性。大脑内神经活动的区域变化通过代谢活动和血流增加导致局部热平衡的改变。我们使用红外成像来可视化大脑体感皮层中刺激诱导的变化，研究了麻醉大鼠中温度变化与神经活动之间的关系。使用振动毛刷（胡须）以 10 Hz、5 Hz 和 1 Hz 的频率进行 10 s 的感觉刺激。观测区域的脑温在胡须刺激下继续显著升高。在 10 Hz、5 Hz 和 1 Hz 时，记录到的平均峰值温度变化分别为 0.048±0.028°C、0.054±0.036°C 和 0.097±0.015°C。我们还观察到，在单次胡须刺激时，温度升高出现在一个焦点上，向对侧桶状皮层区域的更大区域辐射。胡须刺激还导致同侧皮层温度升高，其定位于软脑膜小动脉所在的同一区域。用钙通道阻滞剂（尼莫地平）处理的大鼠也观察到了桶状皮层的温度升高，尼莫地平作用是抑制神经活动的血液动力学反应。因此，温度升高的位置和面积与神经激活的区域相符。这些结果表明，IR 热成像作为一种功能定量神经影像学技术是可行的。
