神经反馈是一种能够使人们自主调控大脑活动的新技术，即通过实时观测和提取个体的大脑活动信号，并将该信号以视觉或听觉等形式直观地反馈给该个体，使其能够寻找合适的策略以实现自主地调控大脑活动。已有研究发现，利用神经反馈技术调控大脑活动的同时会伴随个体相应的认知和行为改变；如果通过长时间的神经反馈训练，则可以实现个体相应认知或行为能力的改善，甚至有助于精神或神经疾病的康复。这表明神经反馈技术在基础与临床神经科学领域具有重要的应用前景：一方面为研究大脑活动模式与行为之间的关系提供了一种更为因果的方式；另一方面可以通过对大脑活动的自主调控训练实现认知和行为能力的改善，为精神或神经疾病提供新的康复方法。我们在国际上首次提出脑间耦合神经反馈新概念，即通过同时观测两个（甚至多个）被试的大脑活动，实时计算他们的脑间神经活动交互性（如脑间同步性等）并以直观的形式将该信号反馈给两位被试；两位被试在共同反馈信号的指引下，寻找合适的策略以实现调控他们的脑间交互关系。已有研究发现，人类在进行社会交互（如合作、面对面交流等）时，参与者大脑特定区域之间同样会存在交互现象，而有社交障碍的群体（如自闭症患者）在社会交互中的脑间交互异常。如果人类能够通过调控脑间交互来改善社会行为，那么对于理解人类社会交互的神经机制，以及开发社交障碍等疾病的新疗法都将具有重要的科学意义与实践价值。脑间耦合神经反馈需要在自然交互条件下同时观测两人(或者多人)的脑活动。在现有脑成像技术中，功能近红外光学成像在这方面具有独特的优势。fNIRS是一种非侵入式的光学脑成像设备，利用脑组织血红蛋白对不同波长的近红外光吸收率的差异特性，可以检测大脑皮层的血液动力学活动，进而研究大脑神经活动。fNIRS设备轻便可移动，扫描环境舒适无噪声，对头动不敏感，被试不需要被限制在狭小的扫描腔内，两名被试可以面对面通过语言、肢体动作进行交流。此外，fNIRS的各个测量通道间相对独立，可以使用一台fNIRS设备同时测量两名被试，其可移动特性进一步允许将多台fNIRS设备集中于一处进行多人同时测量。fNIRS的上述特性，为高生态效度的脑间耦合神经反馈提供了可能。目前有数篇关于使用fNIRS进行神经反馈研究，提供了用fNIRS进行神经反馈的可行性的证据。关于基于fNIRS的神经反馈平台的具体实现方面，目前还没有公开的系统平台。而在多脑神经反馈领域，作者已发表研究论文首次提出脑间耦合神经反馈新概念及相应平台。为在弥补目前基于fNIRS神经反馈平台的空缺，以及推动进一步推动神经反馈领域的发展。作者设计并实现了神经反馈系列平台，以针对不同硬件条件及神经反馈研究的需求。系列平台包括，单脑神经反馈平台，基于单台fNIRS的高生态效度双脑神经反馈平台，以及基于互联网的多脑神经反馈平台。

Neurofeedback is a new way to help people self-regulating brain activity. This new technology observes and extracts individual brain activity signal, then feedbacks to the individual in visual or auditory forms in real-time. With the feedback signal, people may able to find suitable strategies to achieve self-regulate brain activity. It has been found that use of neurofeedback technology while regulating brain activity will be accompanied by the individual cognitive and behavioral change. If using neurofeedback training for a long time, it can achieve a corresponding improvement in individual cognitive or behavioral abilities, and even help in the rehabilitation of mental or neurological disorders. This suggests that neurofeedback technology in basic and clinical neuroscience has important applications. Firstly, it provides a new paradigm for the study of the relationship between brain activity patterns and behavior in a more causal way. Additionally, the neurofeedback technology provides new methods of rehabilitation for mental or nervous disorders.We first proposed the new concept of cross-brain neurofeedback. This technique simultaneous observes two or more subjects’ brain activity and real-time computes the interactive index of their neural activities, such as synchronization between the brains, and then gives back the interactive index to the two subjects. Two subjects together under the guidance of the feedback signal, finding the right strategy to achieve regulatory interactions between theirs brains. People have found that during human social interaction, such as cooperation, there exists interaction between participants’ brains in specific areas. However, there is abnormal interaction between brains when participants suffered from human communication disorders, such as autism. If human social behavior can be improved through regulation of the interaction between brains, it will have important scientific significance and practical value for understanding the neural mechanisms of new therapies for human society interaction and the development of social barriers and other diseases.Cross-brain neurofeedback observes two or more people’s brain activities in natural condition. In the current brain imaging techniques, functional near-infrared spectroscopy has unique advantages in this regard. fNIRS is a non-invasive optical brain imaging technique. Using the characteristic of different absorption of near-infrared light between HbO and HbR brain tissue, fNIRS can detect hemodynamic activity in cerebral cortex, which reflects neuronal activity. fNIRS device is lightweight and movable. Experiment environment with fNIRS can be comfortable, without noise, not sensitive with head motion. Subjects need not be restricted to a narrow scanning chamber, and can talk face to face through language. Single fNIRS device may simultaneously measure many subjects, as its measurement channels are relatively independent. Additionally, as fNIRS devices are movable, multiple fNIRS devices can be moved in one place and measure multiple subjects in the same time. fNIRS, as described above, is suitable for high ecological validity cross-brain neurofeedback experiment.Currently there are several articles about neurofeedback in fNIRS modal, providing evidence of feasibility of fNIRS based neurofeedback. However, there aren’t any published fNIRS based neurofeedback platforms, except a paper about the concept and platform of cross-brain neurfeedback, which was published by the author’s group.To compensate for the loss of fNIRS based neurofeedback platform, as well as to promote the development of the field of neurofeedback, the author designed and implemented a series of neurofeedback platform, including single brain feedback platform, single fNIRS based cross-brain neurofeedback platform, and internet-based cross-brain neurofeedback platform.