Schmidt Timo Torsten, Wu Yuan-Hao, Blankenburg Felix
Neurocomputation and Neuroimaging Unit, Department of Education and Psychology, Freie Universität Berlin, 14195 Berlin, Germany,
Institute of Cognitive Science, Universität Osnabrück, 49090 Osnabrück, Germany, and.
J Neurosci. 2017 Oct 4;37(40):9771-9777. doi: 10.1523/JNEUROSCI.1167-17.2017. Epub 2017 Sep 11.
To understand how the brain handles mentally represented information flexibly in the absence of sensory stimulation, working memory (WM) studies have been essential. A seminal finding in monkey research is that neurons in the prefrontal cortex (PFC) retain stimulus-specific information when vibrotactile frequencies were memorized. A direct mapping between monkey studies and human research is still controversial. Although oscillatory signatures, in terms of frequency-dependent parametric beta-band modulation, have been observed recently in human EEG studies, the content specificity of these representations in terms of multivariate pattern analysis has not yet been shown. Here, we used fMRI in combination with multivariate classification techniques to determine which brain regions retain information during WM. In a retro-cue delayed-match-to-sample task, human subjects memorized the frequency of vibrotactile stimulation over a 12 s delay phase. Using an assumption-free whole-brain searchlight approach, we tested with support vector regression which brain regions exhibited multivariate parametric WM codes of the maintained frequencies during the WM delay. Interestingly, our analysis revealed an overlap with regions previously identified in monkeys composed of bilateral premotor cortices, supplementary motor area, and the right inferior frontal gyrus as part of the PFC. Therefore, our results establish a link between the WM codes found in monkeys and those in humans and emphasize the importance of the PFC for information maintenance during WM also in humans. Working memory (WM) research in monkeys has identified a network of regions, including prefrontal regions, to code stimulus-specific information when vibrotactile frequencies are memorized. Here, we performed an fMRI study during which human subjects had to memorize vibratory frequencies in parallel to previous monkey research. Using an assumption-free, whole-brain searchlight decoding approach, we identified for the first time regions in the human brain that exhibit multivariate patterns of activity to code the vibratory frequency parametrically during WM. Our results parallel previous monkey findings and show that the supplementary motor area, premotor, and the right prefrontal cortex are involved in vibrotactile WM coding in humans.
为了了解大脑如何在没有感官刺激的情况下灵活处理心理表征信息，工作记忆（WM）研究至关重要。猴子研究中的一项开创性发现是，当记忆振动触觉频率时，前额叶皮层（PFC）中的神经元会保留特定刺激信息。猴子研究与人类研究之间的直接映射仍存在争议。尽管最近在人类脑电图研究中观察到了振荡特征，即频率依赖性参数β波段调制，但这些表征在多变量模式分析方面的内容特异性尚未得到证实。在这里，我们将功能磁共振成像（fMRI）与多变量分类技术相结合，以确定在工作记忆期间哪些脑区保留信息。在一项逆向线索延迟匹配样本任务中，人类受试者在12秒的延迟阶段记忆振动触觉刺激的频率。使用无假设的全脑搜索光方法，我们用支持向量回归测试了哪些脑区在工作记忆延迟期间表现出维持频率的多变量参数工作记忆编码。有趣的是，我们的分析揭示了与先前在猴子中确定的区域重叠，这些区域由双侧运动前皮层、辅助运动区和作为PFC一部分的右额下回组成。因此，我们的结果在猴子和人类中发现的工作记忆编码之间建立了联系，并强调了PFC在人类工作记忆期间信息维持中的重要性。猴子的工作记忆研究已经确定了一个区域网络，包括前额叶区域，当记忆振动触觉频率时对特定刺激信息进行编码。在这里，我们进行了一项功能磁共振成像研究，在此期间，人类受试者必须像之前的猴子研究一样并行记忆振动频率。使用无假设的全脑搜索光解码方法，我们首次在人类大脑中确定了在工作记忆期间表现出多变量活动模式以对振动频率进行参数编码的区域。我们的结果与之前猴子的发现相似，表明辅助运动区、运动前区和右前额叶皮层参与了人类的振动触觉工作记忆编码。
