Intaitė Monika, Duarte João Valente, Castelo-Branco Miguel
Visual Neuroscience Laboratory - IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
Visual Neuroscience Laboratory - IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
Brain Res. 2016 Nov 1;1650:142-151. doi: 10.1016/j.brainres.2016.08.044. Epub 2016 Aug 31.
A visual stimulus is defined as ambiguous when observers perceive it as having at least two distinct and spontaneously alternating interpretations. Neuroimaging studies suggest an involvement of a right fronto-parietal network regulating the balance between stable percepts and the triggering of alternative interpretations. As spontaneous perceptual reversals may occur even in the absence of attention to these stimuli, we investigated neural activity patterns in response to perceptual changes of ambiguous Necker cube under different amounts of working memory load using a dual-task design. We hypothesized that the same regions that process working memory load are involved in perceptual switching and confirmed the prediction that perceptual reversals led to fMRI responses that linearly depended on load. Accordingly, posterior Superior Parietal Lobule, anterior Prefrontal and Dorsolateral Prefrontal cortices exhibited differential BOLD signal changes in response to perceptual reversals under working memory load. Our results also suggest that the posterior Superior Parietal Lobule may be directly involved in the emergence of perceptual reversals, given that it specifically reflects both perceptual versus real changes and load levels. The anterior Prefrontal and Dorsolateral Prefrontal cortices, showing a significant interaction between reversal levels and load, might subserve a modulatory role in such reversals, in a mirror symmetric way: in the former activation is suppressed by the highest loads, and in the latter deactivation is reduced by highest loads, suggesting a more direct role of the aPFC in reversal generation.
当观察者将视觉刺激感知为具有至少两种不同且自发交替的解释时，该视觉刺激被定义为具有歧义性。神经影像学研究表明，右额顶叶网络参与调节稳定感知与触发替代解释之间的平衡。由于即使在未关注这些刺激的情况下也可能发生自发的感知反转，我们使用双任务设计，研究了在不同工作记忆负荷量下，对歧义性内克尔立方体的感知变化做出反应时的神经活动模式。我们假设处理工作记忆负荷的相同区域也参与感知切换，并证实了感知反转会导致功能磁共振成像（fMRI）反应呈线性依赖于负荷的预测。相应地，顶叶上小叶后部、前额叶前部和背外侧前额叶皮质在工作记忆负荷下对感知反转表现出不同的血氧水平依赖（BOLD）信号变化。我们的结果还表明，顶叶上小叶后部可能直接参与感知反转的出现，因为它特别反映了感知与实际变化以及负荷水平。前额叶前部和背外侧前额叶皮质显示出反转水平与负荷之间的显著相互作用，可能以镜像对称的方式在此类反转中发挥调节作用：在前者中，最高负荷会抑制激活，而在后者中，最高负荷会减少去激活，这表明前额叶前部皮质在反转产生中发挥更直接的作用。
