Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Sciences (DINOGMI), University of Genova, Genova, Italy; Laboratory of Medical Physics and Magnetic Resonance, IRCCS Stella Maris, Pisa, Italy.
Curr Biol. 2021 Aug 9;31(15):3401-3408.e4. doi: 10.1016/j.cub.2021.05.026. Epub 2021 Jun 9.
The mechanisms coordinating action and perception over time are poorly understood. The sensory cortex needs to prepare for upcoming changes contingent on action, and this requires temporally precise communication that takes into account the variable delays between sensory and motor processing. Several theorists have proposed synchronization of the endogenous oscillatory activity observed in most regions of the brain as the basis for an efficient and flexible communication protocol between distal brain areas, a concept known as "communication through coherence." Synchronization of endogenous oscillations occurs after a salient sensory stimulus, such as a flash or a sound, and after a voluntary action, and this directly impacts perception, causing performance to oscillate rhythmically over time. Here we introduce a novel fMRI paradigm to probe the neural sources of oscillations, based on the concept of perturbative signals, which overcomes the low temporal resolution of BOLD signals. The assumption is that a synchronized endogenous rhythm will modulate cortical excitability rhythmically, which should be reflected in the BOLD responses to brief stimuli presented at different phases of the oscillation cycle. We record rhythmic oscillations of V1 BOLD synchronized by a simple voluntary action, in phase with behaviorally measured oscillations in visual sensitivity in the theta range. The functional connectivity between V1 and M1 also oscillates at the same rhythm. By demonstrating oscillatory temporal coupling between primary motor and sensory cortices, our results strongly implicate communication through coherence to achieve precise coordination and to encode sensory-motor timing.
目前，人们对协调动作和感知随时间变化的机制知之甚少。感觉皮层需要根据动作准备好即将到来的变化，这就需要时间上精确的通信，考虑到感觉和运动处理之间的可变延迟。几位理论家提出，将大脑大多数区域中观察到的内源性振荡活动同步作为远程脑区之间有效且灵活的通信协议的基础，这一概念被称为“相干通信”。在显著的感觉刺激（如闪光或声音）之后以及自愿动作之后，会出现内源性振荡的同步，这直接影响感知，导致性能随时间呈周期性波动。在这里，我们引入了一种新的 fMRI 范式来探测基于微扰信号概念的振荡的神经源，该范式克服了 BOLD 信号的时间分辨率低的问题。假设同步的内源性节律将周期性地调制皮层兴奋性，这应该反映在 BOLD 对在振荡周期的不同相位呈现的短暂刺激的响应中。我们记录了由简单自愿动作同步的 V1 BOLD 的节律性振荡，与视觉灵敏度在 theta 范围内的行为测量的振荡相位一致。V1 和 M1 之间的功能连接也以相同的节奏振荡。通过证明初级运动和感觉皮层之间的振荡时间耦合，我们的结果强烈表明，通过相干通信来实现精确协调和编码感觉运动时间。
