Helen Wills Neuroscience Institute and Department of Psychology, University of California, Berkeley, CA, USA.
Department of Psychological and Brain Sciences and the Iowa Neuroscience Institute, The University of Iowa, Iowa, IA, USA.
Cereb Cortex. 2020 Mar 14;30(3):875-887. doi: 10.1093/cercor/bhz133.
Past studies have demonstrated that flexible interactions between brain regions support a wide range of goal-directed behaviors. However, the neural mechanisms that underlie adaptive communication between brain regions are not well understood. In this study, we combined theta-burst transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging to investigate the sources of top-down biasing signals that influence task-evoked functional connectivity. Subjects viewed sequences of images of faces and buildings and were required to detect repetitions (2-back vs. 1-back) of the attended stimuli category (faces or buildings). We found that functional connectivity between ventral temporal cortex and the primary visual cortex (VC) increased during processing of task-relevant stimuli, especially during higher memory loads. Furthermore, the strength of functional connectivity was greater for correct trials. Increases in task-evoked functional connectivity strength were correlated with increases in activity in multiple frontal, parietal, and subcortical (caudate and thalamus) regions. Finally, we found that TMS to superior intraparietal sulcus (IPS), but not to primary somatosensory cortex, decreased task-specific modulation in connectivity patterns between the primary VC and the parahippocampal place area. These findings demonstrate that the human IPS is a source of top-down biasing signals that modulate task-evoked functional connectivity among task-relevant cortical regions.
过去的研究表明，大脑区域之间的灵活相互作用支持广泛的目标导向行为。然而，大脑区域之间适应性交流的神经机制还不是很清楚。在这项研究中，我们结合了 theta 爆发经颅磁刺激（TMS）和功能磁共振成像，以研究影响任务诱发功能连接的自上而下偏向信号的来源。被试观看面孔和建筑物的图像序列，并被要求检测所关注刺激类别的重复（2 次与 1 次）（面孔或建筑物）。我们发现，腹侧颞叶皮层和初级视觉皮层（VC）之间的功能连接在处理与任务相关的刺激时增加，尤其是在更高的记忆负荷下。此外，正确试验的功能连接强度更大。任务诱发的功能连接强度的增加与多个额、顶叶和皮质下（尾状核和丘脑）区域的活动增加相关。最后，我们发现，顶内沟（IPS）的 TMS，但不是初级体感皮层的 TMS，降低了初级 VC 和海马旁回位置区之间连接模式的任务特异性调制。这些发现表明，人类 IPS 是自上而下偏向信号的来源，这些信号调节与任务相关的皮质区域之间的任务诱发功能连接。
