|Thesis Advisor||蒋田仔 研究员|
|Place of Conferral||北京|
|Keyword||功能近红外光谱成像技术 神经血管耦合 视觉 半球差异 意识障碍|
|Other Abstract||Functional near-infrared spectroscopy (fNIRS) has emerged as a newly developed non-invasive optical neuroimaging technology, which provides more information about the hemodynamic responses with improved ecological validity by measuring deoxygenated (HbR), oxygenated (HbO), and total (HbT) hemoglobin; moreover, it’s safe, portable, cost-effective, ecological, and can be used for longitudinal monitoring. In this paper, on the one hand, fNIRS was combined with EEG as a multimodal neuroimaging technique to investigate neurovascular couping and hemispheric differences in visual cortex; on the other hand, a self-designed fNIRS system (NEG) was used to investigate the brain activation under several classical tasks as well as to explore the brain activation under brain disorders.|
(1) Brain functional activity involves neuronal electrophysiological signal transmission, energy metabolism, and chemical transmitter release, making it difficult to comprehend. Electroencephalography (EEG) and fNIRS have been combined into a multimodal neuroimaging method that captures both electrophysiological and hemodynamic information to explore the spatiotemporal characteristics of brain activity. Because of the significance of visually evoked functional activity in clinical applications, numerous studies have explored the amplitude of the visual evoked potential (VEP) to clarify its relationship with the hemodynamic response. However, relatively few studies have investigated the influence of latency, which has been frequently used to diagnose visual diseases, on the hemodynamic response. Moreover, because the latency and the amplitude of VEPs have different roles in coding visual information, investigating the relationship between latency and the hemodynamic response should be helpful. In this study, checkerboard reversal tasks with graded contrasts were used to evoke visual functional activity. Both EEG and fNIRS were employed to investigate the relationship between neuronal electrophysiological activities and the hemodynamic responses. The VEP amplitudes were linearly correlated with the hemodynamic response, but the VEP latency showed a negative linear correlation with the hemodynamic response.
(2) Most of the studies of visual system have either focused on distinct stimulus contrasts in full visual field or on distinct visual fields with a constant contrast. However, hemispheric differences in neuronal activities, hemodynamic responses, and neurovascular coupling remain unclear. A multimodal neuroimaging technique based on EEG and fNIRS was used with horizontal hemifield visual stimuli with graded contrasts to investigate the retinotopic mapping more fully as well as to explore hemispheric differences in neuronal activity, the hemodynamic response, and the neurovascular coupling relationship in the visual cortex. The fNIRS results showed the expected activation over the contralateral hemisphere for both the left and right hemifield visual stimulations. However, the EEG results presented a paradoxical lateralization, with the maximal response located over the ipsilateral hemisphere but with the polarity inversed components located over the contralateral hemisphere. Our results suggest that the polarity inversion as well as the latency advantage over the contralateral hemisphere cause the amplitude of the VEP over the contralateral hemisphere to be smaller than that over the ipsilateral hemisphere. Both the neuronal and hemodynamic responses changed logarithmically with the level of contrast in the hemifield visual stimulations. Moreover, the amplitudes and latencies of the visual evoked potentials (VEPs) were linearly correlated with the hemodynamic responses despite differences in the slopes.
(3) A self-designed fNIRS system (NEG) was used to investigate the functional activation of the brain. Since the NEG system is one of the medical devices, several classic tasks were conducted to evaluate the performance of hemodynamic detection before it can be used in the clinical environment. The results showed that the hemodynamic responses could be recorded over the corresponding brain areas under different tasks, and suggested that the NEG system has a relatively good performance. The evalutation of the performance of the NEG system has great significance to promote the clinical application and optimization of the system as well as to further promote the process of industrialization.
(4) Spinal cord stimulation (SCS) has relatively good therapeutic effects on patients with disorders of consciousness (DOC), but the underlying mechanism remains unclear. In addition, the design of SCS parameters is an important part of postoperative treatment. At present, the design of SCS parameters mainly depends on the subjective experience and behavior evaluation of clinicians. There is still a lack of evidence-based evaluation method to quantitantively assess the effects of SCS. In view of this situation, we first used fNIRS to investigate the neuromodulation effects of SCS on patients with DOC. Several SCS protocols with different stimulation inter-stimulus intervals and frequencies were conducted to study the brain activation of the patients with DOC. Our research goals were to reveal the mechanism of SCS and to provide guidance for designing SCS parameters. Our results showed that SCS could induce the changes in hemodynamic responses of the brain for patients with DOC; moreover, the changing patterns of hemodynamic responses under different SCS parameters were distinct.
|司娟宁. 基于功能近红外光谱成像技术的脑功能研究[D]. 北京. 中国科学院研究生院,2017.|
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