NON-INVASIVE OPTICAL IMAGING OF THE HUMAN BRAIN

近红外光谱（NIRS）是一种潜在的有效的非侵入性人脑功能研究技术。该技术的优势在于其对脑氧和脱氧血红蛋白浓度（分别为[HbO2]和[Hb]）的高灵敏度，因此对脑血流动力学的高灵敏度，以及在10 ms范围内的高时间分辨率。虽然近红外光谱在脑功能研究中取得了非常有希望的结果，但在近红外光谱成功应用于临床工具之前，仍有许多悬而未决的问题有待解答。例如，基线血流动力学在以下发现中发挥了什么作用：1激活的皮层区域在[Hb]图中比在[HbO2]图中更好地定位，2激活后皮层血红蛋白饱和度显著增加？高波动基线光信号的生理起源是什么？是否可以利用这些基线的大脑信号来提取生理和潜在的诊断参数？此外，近红外光谱能否无创检测到延迟时间为50-100 ms的快速神经激活？本研究旨在解决这些问题，目的是描述脑血流动力学基线的时空特征和大脑激活引起的近红外反应。为了实现这一目标，我们将对健康受试者在休息、视觉或运动刺激时的大脑区进行空间分辨频域频谱测量（波长范围630-850 nm）。在进行光学测量的同时，我们将持续监测全身生理参数，如心率、动脉饱和度、呼吸时间模式和平均动脉血压。本研究为实现婴儿脑氧合持续监测、脑血管疾病和精神综合征诊断和随访的创新临床工具迈出了第一步。

Near-infrared spectroscopy (NIRS) is a potentially effective technique for non-invasive functional studies of the human brain. The strengths of this technique are its high sensitivity to cerebral oxy- and deoxy-hemoglobin concentrations ([HbO2] and [Hb], respectively), and therefore to the cerebral hemodynamics, and its high temporal resolution in the 10 ms range. While NIRS has yielded very promising results in functional brain studies, there are a number of open questions that await an answer before NIRS can be successfully applied as a clinical tool. For instance, what is the role played by the baseline hemodynamics in the findings the 1 the activated cortex area is better localized in [Hb] maps than in [HbO2] maps, and 2 the cortex hemoglobin saturation increases substantially upon activation? What is the physiological origin of the highly fluctuating baseline optical signals? Can these baseline cerebral signals be exploited to extract physiological and potentially diagnostic parameters? Furthermore, can NIRS non-invasively detect the fast neural activation, occurring with a latency of 50-100 ms? This proposal aims at addressing these issues with the goal of characterizing the temporal-spatial features of the baseline cerebral hemodynamics and of the near-infrared response evoked by cerebral activation. To achieve this goal, we will perform spatially- resolved, frequency-domain spectral measurements (in the wavelength range 630-850 nm) over large brain areas of healthy subjects at rest, and during visual or motor stimulation. Simultaneously with the optical measurements, we will continuously monitor systemic physiological parameters such as the heart rate, the arterial saturation, the breathing temporal pattern, and the mean arterial blood pressure. This research constitutes a first step toward the realization of innovative clinical tools for the continuous monitoring of cerebral oxygenation in infants, and for the diagnosis and follow-up of cerebrovascular diseases and psychiatric syndromes.