古希腊先哲亚里斯多德认为，循环系统是思想和情感之源。这一观点长久以来被人认为不可想象。但美国麻省理工学院的一个科学家小组日前近日提出一种假说，血液的作用不仅仅在于输送燃料和氧气，血液可以帮助我们思考，因为它能够积极地调整神经元处理信息的方式。 这一假说若得到证实，将会改变我们对大脑工作方式的认识。相关论文10月3日发表在《神经生理学杂志》(Journal of Neurophysiology)上。
该假说称为血液-神经假说，由麻省理工学院McGovern脑研究所的Christopher Moore提出。该假说认为，血液并不仅仅是生理学上的支撑系统，它也能帮助控制大脑的活动。具体来说，血流的局部变化会影响邻近神经细胞的活性，从而改变它们之间信号的传输方式，最终调节输入大脑的信息。Moore实验室正在进行的研究支持了这一观点，认为血流确实能够调节单个神经细胞。
那么，血流是怎样影响脑部活动的？研究小组称，血液含有能够穿透血管影响神经元活动的溶解因子，血流量的改变也可能会影响到溶解因子的浓度。此外，神经元和神经胶质细胞也会对血管的扩张和收缩产生反应。最后，脑组织的温度会在血液的影响下发生变化，从而影响到神经元的活动。因此穆尔认为，应该用全新的方式来看待人的大脑，血液系统可能是决定大脑活动的主要因素。
这一假说对于理解早老性痴呆、精神分裂症、癫痫等脑部疾病有重要意义。Moore表示，很多神经学及精神病学方面的疾病都与脉管系统的变化有关。他说：“大多数人认为，这些疾病的症状是神经损伤的后果。但是我们认为，这些症状有可能也是导致疾病发展的因素。这种认识有可能导致全新的治疗方式。”以癫痫为例，这类病人脑部通常有异常的血管存在，血液-神经假说认为这些反常的血流可能就是诱发癫痫的原因。如果确实如此，人们将有可能开发出有效的针对性药物来治疗癫痫。
这一假设对磁共振成像技术也有重要意义，磁共振成像是用来了解大脑血流变化的常用扫描手段。麻省理工学院的科学家认为，如果我们知道了血液对神经元活动的影响，就可以利用磁共振成像来了解大脑的信息处理过程。
Moore认为，这一假说提供了全新的认识脑部活动的方法，而之前人们从来没有把血流纳入大脑处理信息的模型中。
原始出处:
J Neurophysiol (October 3, 2007). doi:10.1152/jn.01366.2006
The Hemo-Neural Hypothesis: On The Role of Blood Flow in Information Processing
Christopher Irwin Moore1* and Rosa Cao1
1 McGovern Institute for Brain Research, MIT, Cambridge, Massachusetts, United States
* To whom correspondence should be addressed. E-mail: cimoore4@mit.edu .
Brain vasculature is a complex and interconnected network under tight regulatory control that exists in intimate communication with neurons and glia. Typically, hemodynamics are considered to exclusively serve as a metabolic support system. In contrast to this canonical view, we propose that hemodynamics also play a role in information processing through modulation of neural activity. Functional hyperemia, the basis of the fMRI BOLD signal, is a localized influx of blood correlated with neural activity levels. Functional hyperemia is considered by many to be excessive from a metabolic standpoint, but may be appropriate if interpreted as having an activity-dependent neuro-modulatory function. Hemodynamics may impact neural activity through direct and indirect mechanisms. Direct mechanisms include delivery of diffusible blood-borne messengers, and mechanical and thermal modulation of neural activity. Indirect mechanisms are proposed to act through hemodynamic modulation of astrocytes, which can in turn regulate neural activity. These hemo-neural mechanisms should alter the information processing capacity of active local neural networks. Here, we focus on analysis of neocortical sensory processing. We predict that hemodynamics alter the gain of local cortical circuits, modulating the detection and discrimination of sensory stimuli. This novel view of information processing, that includes hemodynamics as an active and significant participant, has implications for understanding neural representation and the construction of accurate brain models. There are also potential medical benefits of an improved understanding of the role of hemodynamics in neural processing, as it directly bears on interpretation of and potential treatment for stroke, dementia and epilepsy.
