Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata 951-8585, Japan.
Primate Research Institute, Kyoto University, Inuyama City, Aichi 484-8506, Japan.
eNeuro. 2017 Oct 30;4(5). doi: 10.1523/ENEURO.0183-17.2017. eCollection 2017 Sep-Oct.
The neural processes underlying self-initiated behavior (behavior that is initiated without an external stimulus trigger) are not well understood. This event-related fMRI study investigated the neural origins of self-initiated behaviors in humans, by identifying brain regions that increased in neural activities several seconds prior to self-initiated movements. Subjects performed a hand grasping task under two conditions: a free-timing and cued timing condition. The supplementary motor area (SMA) began to activate several seconds prior to self-initiated movement (accounting for hemodynamic delay), representing a potential blood oxygenation level-dependent (BOLD) signal correlate of the readiness potential (RP) on electroencephalogram (EEG), referred to here as "readiness BOLD signals." Significant readiness BOLD signals were also observed in the right frontoparietal areas, precuneus, and insula, all of which are known to contribute to internally-generated behaviors, but with no prior evidence for such early and slow accumulation of neural activities. Moreover, visual and auditory cortices also exhibited clear readiness BOLD signals with similar early onsets, even absent external stimulation. Slow accumulation of neural activities throughout distributed cortical areas, including sensory, association, and motor cortices, underlies the generation of self-initiated behaviors. These findings warrant reconsideration of the prevailing view that the SMA or some other specific locus in frontoparietal cortex serves as the ultimate neural origin of self-initiated movement.
自我启动行为（无需外部刺激触发即可启动的行为）的神经过程尚未得到很好的理解。这项事件相关的 fMRI 研究通过识别在自我启动运动前几秒内神经活动增加的脑区，探讨了人类自我启动行为的神经起源。在两种条件下，被试执行手部抓握任务：自由计时和提示计时条件。补充运动区（SMA）在自我启动运动前几秒钟开始激活（考虑到血液动力学延迟），代表脑电图（EEG）上准备电位（RP）的潜在血氧水平依赖性（BOLD）信号相关物，此处称为“准备 BOLD 信号”。在右额顶叶区域、顶下小叶和脑岛也观察到显著的准备 BOLD 信号，这些区域都已知有助于内部产生的行为，但以前没有证据表明这些区域会有如此早期和缓慢的神经活动积累。此外，即使没有外部刺激，视觉和听觉皮层也表现出明显的准备 BOLD 信号，具有相似的早期发作。自我启动行为的产生是基于分布在整个皮质区域的神经活动的缓慢积累，包括感觉、联合和运动皮层。这些发现值得重新考虑当前的观点，即 SMA 或额顶叶皮层的其他特定部位是自我启动运动的最终神经起源。
