Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, Tübingen, Germany.
Magn Reson Imaging. 2010 Oct;28(8):1087-94. doi: 10.1016/j.mri.2009.12.028. Epub 2010 Feb 19.
The fMRI-BOLD contrast is widely used to study the neural basis of sensory perception and cognition. This signal, however, reflects neural activity only indirectly, and the detailed mechanisms of neurovascular coupling and the neurophysiological correlates of the BOLD signal remain debated. Here we investigate the coupling of BOLD and electrophysiological signals in the motion area MT of the macaque monkey by simultaneously recording both signals. Our results demonstrate that a prominent neuronal response property of area MT, so-called motion opponency, can be used to induce dissociations of BOLD and neuronal firing. During the presentation of a stimulus optimally driving the local neurons, both field potentials [local field potentials (LFPs)] and spiking activity [multi-unit activity (MUA)] correlated with the BOLD signal. When introducing the motion opponency stimulus, however, correlations of MUA with BOLD were much reduced, and LFPs were a much better predictor of the BOLD signal than MUA. In addition, for a subset of recording sites we found positive BOLD and LFP responses in the presence of decreases in MUA, regardless of the stimulus used. Together, these results demonstrate that correlations between BOLD and MUA are dependent on the particular site and stimulus paradigm, and foster the notion that the fMRI-BOLD signal reflects local dendrosomatic processing and synaptic activity rather than principal neuron spiking responses.
功能磁共振成像（fMRI）中的血氧水平依赖（BOLD）对比被广泛用于研究感觉感知和认知的神经基础。然而，这种信号仅间接地反映了神经活动，神经血管耦合的详细机制以及 BOLD 信号的神经生理学相关性仍存在争议。在这里，我们通过同时记录这两种信号来研究猕猴运动区 MT 中的 BOLD 和电生理信号的耦合。我们的结果表明，运动区 MT 的一种显著的神经元反应特性，即所谓的运动拮抗，可以用来诱导 BOLD 和神经元放电的分离。在呈现最佳驱动局部神经元的刺激时，场电位（LFPs）和尖峰活动（MUA）都与 BOLD 信号相关。然而，当引入运动拮抗刺激时，MUA 与 BOLD 的相关性大大降低，而 LFPs 比 MUA 更能预测 BOLD 信号。此外，对于一部分记录位点，我们发现无论使用何种刺激，MUA 减少的同时都会出现 BOLD 和 LFP 的正响应。这些结果表明，BOLD 和 MUA 之间的相关性取决于特定的部位和刺激范式，并促进了 fMRI-BOLD 信号反映局部树突体处理和突触活动而不是主要神经元放电反应的观点。
