Near-infrared (NIR) light has been shown to produce a range of physiological effects in humans, however, there is still no agreement on whether and how a single parameter, like the flicker frequency of NIR light, affects the brain. An 810 nm NIR LED was used as the stimulator. Fifty subjects participated in this experiment. Forty subjects were randomly divided into four groups. Each group underwent a 30-minute NIR LED radiation with four different frequencies (i.e., 0 Hz, 5 Hz, 10Hz and 20 Hz, respectively) on the forehead. The remaining 10 subjects formed the control group, in which they underwent a 30-minute rest period without light radiation. EEG signals of all subjects during each test were recorded. Gravity frequency (GF), relative energy change, and sample entropy were analyzed. The experimental groups had larger GF values compared to the control group. Higher stimulation frequency would cause larger growth of GF (F = 14.75, P < 0.001). The amplitude of alpha waves relative energy increased, while theta waves decreased remarkably in the experimental groups (p < 0.02), and the extent of increase/decrease was larger at higher stimulation frequency, compared to that of the control. Sample entropy of electrodes in the frontal areas were much larger than those in other brain areas in the experimental groups (p < 0.001). Larger frequency of the NIR LED light would cause more distinct brain activities in the stimulated areas. It indicates that NIR LEDlightmay have a positive effect onmodulating brain activity.These resultsmay help improve the design of photobiomodulation treatments in the future.

Laser speckle contrast imaging (LSCI) is an optical imaging method, which can monitor microvascular flow variation directly without addition of any ectogenous dye. All the existing laser speckle contrast analysis (LASCA) methods are a combination of spatial and temporal statistics. In this study, we have proposed a new method, Gaussian kernel laser speckle contrast analysis (gLASCA), which processes the raw images primarily with the Gaussian kernel operator along the spatial direction of blood flow. We explored the properties of gLASCA in the simulation and animal cerebral ischemia perfusion model. Compared with the other existing speckle processing methods based on spatial, temporal, spatial-temporal or anisotropic linear structure; the present gLASCA method has a high spatial-temporal resolution to respond the change of velocity especially in microvasculature. Besides, the gLASCA method obtains approximately 10.2% and 7.1% higher contrast-to-noise ratio (CNR) over the anisotropic linear method (aLASCA) in the simulation and experiment models. For these advantages, gLASCA could be a better method for local microvascular laser speckle imaging in terms of cerebral ischemia reperfusion, spreading depression and brain injury diseases.

The stereo vision results from the interaction between geometrical optics and visual psychology. Large depth will bring discomforts for the results of ghosting and flicker. The relevance of the ratio of jumping out depth (RJD) and electroencephalogram (EEG) gravity frequency (GF) was explored to reflect human health under different three-dimensional (3D) depth information (mainly the negative disparity) displayed on a three-dimensional television (3D-TV) with shutter glasses. EEG was obtained from 10 volunteers when they were watching 3D film segments with different negative disparities. The brain GF map shows that the depth information has a stronger influence on the frontal lobe than on the occipital lobe. For regression analysis, nonlinear curve fittings of GF to RJD in Fp1, F3, O2 and T5 channels were mainly performed when RJD ranged from 0 to 3.4, while linear fittings were performed in some special RJD ranges. It also confirms that RJD above 2.2 may lead to discomfort to human body. Finally, it suggests a suitable RJD range for people to watch from the objective method. The outcomes can be used as a guidance to decrease human discomforts induced by 3D production.

在特定的实验条件下, 利用脑电图仪采集10名志愿者观看4个3D影像的脑电信号, 提取各时段的重心频率(Gravity Frequency , GF), 对重心频率进行数据整合处理；测量志愿者观看3D片源各时段的视差, 并转换为对应的会聚角(Optical Angle), 重心频率与会聚角的值进行相关性分析和曲线拟合处理。结果显示: 经过数据合并处理后, 脑电EEG(electroencephalogram)重心频率与观看3D影像时的会聚角存在一定的线性关系, 拟合优度最高的是三次曲线, 观看3D影像时的会聚角在1.778°～3.254°时重心频率呈现下降趋势, 这说明在此范围可能更容易使人感到不适。

通过采集志愿者观看背景视差过大的3D影片前后的脑电数据, 来研究该效应对人体健康的影响。实验共选取20例有效样本, 利用快速傅里叶变换法(FFT)提取特征波段, 计算出各频带的能量和功率, 并由此得到功率谱和重心频率。此外还设计问卷定性了解志愿者的疲劳程度。根据主观疲劳问卷和对比看前看后的脑电参数, 分析了观看背景视差过大的3D影片后人体脑电信号变化的关系。实验结果表明志愿者看前看后的各项脑电参数出现了改变, 并全部主观反映出现疲劳。因此脑电参数结合主观问卷可成为3D影片疲劳评估的参考指标。