Perception and Eye Movement Laboratory, Department of Neurology, University of Bern, Inselspital, 3010 Bern, Switzerland.
Neuroimage. 2012 Feb 15;59(4):3652-61. doi: 10.1016/j.neuroimage.2011.10.094. Epub 2011 Nov 4.
In the present multi-modal study we aimed to investigate the role of visual exploration in relation to the neuronal activity and performance during visuospatial processing. To this end, event related functional magnetic resonance imaging er-fMRI was combined with simultaneous eye tracking recording and transcranial magnetic stimulation (TMS). Two groups of twenty healthy subjects each performed an angle discrimination task with different levels of difficulty during er-fMRI. The number of fixations as a measure of visual exploration effort was chosen to predict blood oxygen level-dependent (BOLD) signal changes using the general linear model (GLM). Without TMS, a positive linear relationship between the visual exploration effort and the BOLD signal was found in a bilateral fronto-parietal cortical network, indicating that these regions reflect the increased number of fixations and the higher brain activity due to higher task demands. Furthermore, the relationship found between the number of fixations and the performance demonstrates the relevance of visual exploration for visuospatial task solving. In the TMS group, offline theta bursts TMS (TBS) was applied over the right posterior parietal cortex (PPC) before the fMRI experiment started. Compared to controls, TBS led to a reduced correlation between visual exploration and BOLD signal change in regions of the fronto-parietal network of the right hemisphere, indicating a disruption of the network. In contrast, an increased correlation was found in regions of the left hemisphere, suggesting an intent to compensate functionality of the disturbed areas. TBS led to fewer fixations and faster response time while keeping accuracy at the same level, indicating that subjects explored more than actually needed.
在本多模态研究中，我们旨在研究视觉探索与视觉空间处理过程中的神经元活动和表现之间的关系。为此，我们将事件相关功能磁共振成像（er-fMRI）与同步眼动记录和经颅磁刺激（TMS）相结合。两组各 20 名健康受试者在 er-fMRI 期间完成了不同难度水平的角度辨别任务。我们选择注视次数作为视觉探索努力的测量指标，并用广义线性模型（GLM）来预测血氧水平依赖（BOLD）信号的变化。在没有 TMS 的情况下，在双侧额顶皮质网络中发现了视觉探索努力与 BOLD 信号之间的正线性关系，这表明这些区域反映了由于任务需求增加而导致的注视次数增加和更高的大脑活动。此外，注视次数与表现之间的关系表明视觉探索对于视觉空间任务解决的重要性。在 TMS 组中，在 fMRI 实验开始之前，在右侧顶后皮质（PPC）上施加离线 theta 爆发 TMS（TBS）。与对照组相比，TBS 导致右侧额顶网络中与 BOLD 信号变化相关的视觉探索减少，表明网络受到干扰。相比之下，在左侧半球的区域中发现了相关性增加，这表明有意补偿受干扰区域的功能。TBS 导致注视次数减少和反应时间加快，同时保持准确性相同，这表明受试者的探索次数超过了实际需要。
