基于非侵入性脑刺激的认知增强：方法、伦理和应用

作为人类追求卓越的方式之一，基于非侵入性脑刺激的认知增强成为众多学科和公众关注的问题。首先阐述了非侵入性脑刺激的两种主要技术手段(经颅磁刺激和经颅直流刺激)的技术原理及其在提升健康个体认知功能上的应用，并分析了这两种技术可能带来的安全、自主选择、公平等伦理问题，最后总结了该认知增强技术在体育和军事等两个具体领域的应用。未来可进一步提高技术手段的深部脑区刺激能力及该增强技术的持续和真实效果。

Cognitive Enhancement Using Non-invasive Brain Stimulation: Methods,Ethics, Applications

Cognitive enhancement refers to the improvement of cognitive function of normal healthy individuals, cognitive function including perception, attention, memory, learning, planning, reasoning, and problem solving. To pursuit excellence, humans employ a variety of approaches to enhance cognition, including education, drugs, and mental training. Recently, due to the development of neuroscience, substantial interest has been directed at using the non-invasive brain stimulation (NIBS) methods to enhance human cognition. The main NIBS methods include transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). TMS and tDCS could change the level of cortical plasticity to strengthen or weaken the excitement of the cerebral cortex. Specifically, TMS causes electric current generated by changing magnetic field to flow in a small region of the brain via electromagnetic induction, whereas tDCS uses the weak current flowing through the cerebral cortex to intervene or change brain activity. The greatest strengths of TMS and tDCS were able to change neural electrical conductivity and indicate the causal relationship between brain and cognitive or behavioral changes. Moreover, they are both relative secure and cheap. Thus, they are widely used in the improvement of individual basic and higher-order cognitive processes. However, previous studies may not report invalid or contrary results due to publication preference, so the actual and sustained effect from cognitive enhancement using the NIBS methods is difficult to determine.Moreover, cognitive enhancement using the NIBS methods raise a series of ethical issues, such as safety, freedom of choice, and fair. First, the potential safety risk that the direct effects of stimulation on brain structure is still unknown. Thus, it should take cautious to implicate those methods in the juveniles’ sample. Second, it should be pointed out cognitive enhancement using the NIBS methods on the specific group who has access to these techniques will impair social injustice and inequality. Third, the right to make freedom choices should be guaranteed. In some cases, people with specific professions such as the soldier or the astronaut may be reluctant to use cognitive enhancement, and they are forced to use cognitive enhancement in order to perform better.Cognitive enhancement using the NIBS methods are highly implicated in sports and military. In sports, the non-invasive brain stimulation can strengthen the body by improving the performance of hands, legs, and muscle tolerance, and promote the motor function by improving motor awareness and motor coordination, and also improve the psychological status before competitions by elevating an athlete's desire to win. In military, the non-invasive brain stimulation methods were widely used to enhance the cognitive abilities which are important of military performances and combat capabilities of soldiers. For example, considerable evidence found tDCS helps reduce the time and effort needed for learning the military skills, also can change and improve cognitive ability such as visual space and auditory attention, which play an important role in military performance and combat capability.Although there are considerable interests on cognitive enhancement using the NIBS methods and the findings make people understand the brain better, there are some directions that warranted future investigation. Firstly, the better brain stimulation techniques should be developed in future. At present, the brain stimulation techniques can only stimulate the superficial cortex, and they cannot reach the deep nucleus of the brain such as hippocampus and amygdala. Furthermore, the time and space resolution of the brain stimulation techniques are needs to improve. Thus, the stimulating techniques with better performance are needed in future. Secondly, the validity and reliability of the real effect of cognitive enhancement using the NIBS methods need to be verified by large samples. Finally, the implications of cognitive enhancement using the NIBS methods in people's work, education, and lives is also worth investigated in future.