School of Psychology, South China Normal University, Guangzhou, China.
Key Laboratory of Brain, Cognition and Education Sciences (South China Normal University), Ministry of Education, Guangzhou, China.
Brain Behav. 2020 Jul;10(7):e01673. doi: 10.1002/brb3.1673. Epub 2020 Jun 4.
Previous studies suggested temporal limitations of visual object identification in the ventral pathway. Moreover, multivoxel pattern analyses (MVPA) of fMRI activation have shown reliable encoding of various object categories including faces and tools in the ventral pathway. By contrast, the dorsal pathway is involved in reaching a target and grasping a tool, and quicker in processing the temporal dynamics of stimulus change. However, little is known about how activation patterns in both pathways may change according to the temporal dynamics of stimulus change.
Here, we measured fMRI responses of two consecutive stimuli with varying interstimulus intervals (ISIs), and we compared how the two visual pathways respond to the dynamics of stimuli by using MVPA and information-based searchlight mapping.
We found that the temporal dynamics of stimuli modulate responses of the two visual pathways in opposite directions. Specifically, slower temporal dynamics (longer ISIs) led to greater activity and better MVPA results in the ventral pathway. However, faster temporal dynamics (shorter ISIs) led to greater activity and better MVPA results in the dorsal pathway.
These results are the first to show how temporal dynamics of stimulus change modulated multivoxel fMRI activation pattern change. And such temporal dynamic response function in different ROIs along the two visual pathways may shed lights on understanding functional relationship and organization of these ROIs.
先前的研究表明，视觉物体识别在腹侧通路中存在时间限制。此外，功能磁共振成像（fMRI）激活的多体素模式分析（MVPA）已经显示出在腹侧通路中对各种物体类别（包括面孔和工具）进行可靠编码。相比之下，背侧通路参与到达目标和抓取工具，并且在处理刺激变化的时间动态方面更快。然而，对于两条通路中的激活模式如何根据刺激变化的时间动态而变化，我们知之甚少。
在这里，我们测量了具有不同刺激间间隔（ISI）的两个连续刺激的 fMRI 反应，并且我们使用 MVPA 和基于信息的搜索灯映射来比较两条视觉通路如何响应刺激的动态。
我们发现刺激的时间动态以相反的方式调节两条视觉通路的反应。具体来说，较慢的时间动态（较长的 ISI）导致腹侧通路的活性增加和 MVPA 结果更好。然而，较快的时间动态（较短的 ISI）导致背侧通路的活性增加和 MVPA 结果更好。
这些结果首次表明刺激变化的时间动态如何调节多体素 fMRI 激活模式的变化。并且，这些沿两条视觉通路的不同 ROI 中的这种时间动态响应功能可能有助于理解这些 ROI 的功能关系和组织。
