Neurocomputation and Neuroimaging Unit (NNU), Department of Education and Psychology, Freie Universität Berlin, Habelschwerdter Allee 45, 14195 Berlin, Germany; Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.
Neurocomputation and Neuroimaging Unit (NNU), Department of Education and Psychology, Freie Universität Berlin, Habelschwerdter Allee 45, 14195 Berlin, Germany; Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.
Neuroimage. 2018 Feb 1;166:325-334. doi: 10.1016/j.neuroimage.2017.10.059. Epub 2017 Oct 28.
Previous working memory (WM) research based on non-human primate electrophysiology and human EEG has shown that frontal brain regions maintain frequencies of flutter stimulation across different sensory modalities by means of a supramodal parametric WM code. These findings imply that frontal regions encode the memorized frequencies in a sensory-unspecific, quantitative format. Here, we explored which brain regions maintain information about frequencies provided by different sensory modalities at the level of activity pattern across fMRI voxel populations. Moreover, we sought evidence for a supramodal multivariate WM representation. Participants maintained the same set of frequencies of tactile vibration and visual flicker for a 6 s WM delay in a frequency discrimination task. A support vector regression model for multivariate pattern analysis was applied. We observed that sensory cortices were only selective for memoranda of their corresponding modalities, while frontoparietal regions exhibited distinguishable activity patterns to memorized frequencies regardless of sensory modality. A common multivariate code was not evident in our data. Collectively, we show that mnemonic representations for stimulus frequencies are maintained throughout the cortical hierarchy, in line with the suggested transformation of information across different representational formats. Although evidence for a supramodal multivariate code is absent, our findings underpin the generalized role of the frontoparietal cortex for maintaining quantitative information across sensory modalities.
先前基于非人类灵长类动物电生理学和人类 EEG 的工作记忆 (WM) 研究表明，额叶脑区通过超模式参数 WM 码来维持不同感觉模态的颤动刺激频率。这些发现表明，额叶区域以感觉非特异性、定量的格式对记忆的频率进行编码。在这里，我们探讨了在 fMRI 体素群体的活动模式水平上，哪些脑区在维持不同感觉模态提供的频率信息方面发挥作用。此外，我们还寻求了超模式多元 WM 表示的证据。参与者在频率辨别任务中进行 6 秒 WM 延迟，保持相同的一组触觉振动和视觉闪烁频率。应用了用于多元模式分析的支持向量回归模型。我们观察到，感觉皮质仅对其相应模态的记忆项目具有选择性，而额顶区域则表现出与记忆频率有关的可区分的活动模式，而与感觉模态无关。我们的数据中没有明显的共同多元代码。总的来说，我们表明，刺激频率的记忆表示形式在整个皮质层次结构中得以维持，这与跨不同表示形式转换信息的建议一致。尽管缺乏超模式多元代码的证据，但我们的研究结果支持了额顶皮层在维持跨感觉模态的定量信息方面的普遍作用。
