Kim Sunjung, Dalboni da Rocha Josue Luiz, Birbaumer Niels, Sitaram Ranganatha
Institute of Medical Psychology and Behavioral Neurobiology, University of Tuebingen, 72076 Tuebingen, Germany.
St. Jude Children's Research Hospital, Memphis, TN 38111, USA.
Brain Sci. 2024 Jul 16;14(7):713. doi: 10.3390/brainsci14070713.
The Global Neuronal Workspace (GNW) hypothesis states that the visual percept is available to conscious awareness only if recurrent long-distance interactions among distributed brain regions activate neural circuitry extending from the posterior areas to prefrontal regions above a certain excitation threshold. To directly test this hypothesis, we trained 14 human participants to increase blood oxygenation level-dependent (BOLD) signals with real-time functional magnetic resonance imaging (rtfMRI)-based neurofeedback simultaneously in four specific regions of the occipital, temporal, insular and prefrontal parts of the brain. Specifically, we hypothesized that the up-regulation of the mean BOLD activity in the posterior-frontal brain regions lowers the perceptual threshold for visual stimuli, while down-regulation raises the threshold. Our results showed that participants could perform up-regulation (Wilcoxon test, session 1: = 0.022; session 4: = 0.041) of the posterior-frontal brain activity, but not down-regulation. Furthermore, the up-regulation training led to a significant reduction in the visual perceptual threshold, but no substantial change in perceptual threshold was observed after the down-regulation training. These findings show that the up-regulation of the posterior-frontal regions improves the perceptual discrimination of the stimuli. However, further questions as to whether the posterior-frontal regions can be down-regulated at all, and whether down-regulation raises the perceptual threshold, remain unanswered.
全球神经元工作空间（GNW）假说指出，只有当分布式脑区之间反复的长距离相互作用激活从后部区域延伸到前额叶区域的神经回路，且超过一定的兴奋阈值时，视觉感知才能进入意识觉知。为了直接验证这一假说，我们训练了14名人类参与者，通过基于实时功能磁共振成像（rtfMRI）的神经反馈，同时在大脑枕叶、颞叶、岛叶和前额叶的四个特定区域增加血氧水平依赖（BOLD）信号。具体而言，我们假设后额叶脑区平均BOLD活动的上调会降低视觉刺激的感知阈值，而下调则会提高阈值。我们的结果表明，参与者能够实现后额叶脑区活动的上调（Wilcoxon检验，第1阶段： = 0.022；第4阶段： = 0.041），但无法实现下调。此外，上调训练导致视觉感知阈值显著降低，但下调训练后未观察到感知阈值有实质性变化。这些发现表明，后额叶区域的上调改善了对刺激的感知辨别。然而，后额叶区域是否根本无法下调，以及下调是否会提高感知阈值等进一步的问题，仍未得到解答。
