Department of Neurology and Bernstein Center for Computational Neuroscience, Charité, Philippstrasse 13, House 6, 10115 Berlin, Germany.
J Neurosci. 2010 Mar 24;30(12):4496-502. doi: 10.1523/JNEUROSCI.6041-09.2010.
Previous animal research has revealed neuronal activity underlying short-term retention of vibrotactile stimuli, providing evidence for a parametric representation of stimulus frequency in primate tactile working memory (Romo et al., 1999). Here, we investigated the neural correlates of vibrotactile frequency processing in human working memory, using noninvasive electroencephalography (EEG). Participants judged the frequencies of vibrotactile stimuli delivered to the fingertip in a delayed match-to-sample frequency discrimination task. As expected, vibrotactile stimulation elicited pronounced steady-state evoked potentials, which were source-localized in primary somatosensory cortex. Furthermore, parametric analysis of induced EEG responses revealed that the frequency of stimulation was reflected by systematic modulations of synchronized oscillatory activity in nonprimary cortical areas. Stimulus processing was accompanied by frequency-dependent alpha-band responses (8-12 Hz) over dorsal occipital cortex. The critical new finding was that, throughout the retention interval, the stimulus frequency held in working memory was systematically represented by a modulation in prefrontal beta activity (20-25 Hz), which was source-localized to the inferior frontal gyrus. This modulation in oscillatory activity during stimulus retention was related to successful frequency discrimination, thus reflecting behaviorally relevant information. Together, the results complement previous findings of parametric working memory correlates in nonhuman primates and suggest that the quantitative representation of vibrotactile frequency in sensory memory entails systematic modulations of synchronized neural activity in human prefrontal cortex.
先前的动物研究揭示了振动触觉刺激短期保留的神经元活动，为灵长类动物触觉工作记忆中刺激频率的参数表示提供了证据（Romo 等人，1999 年）。在这里，我们使用非侵入性脑电图（EEG）研究了人类工作记忆中振动触觉频率处理的神经相关性。参与者在延迟匹配样本频率辨别任务中判断指尖接收到的振动触觉刺激的频率。正如预期的那样，振动触觉刺激引起了明显的稳态诱发电位，这些电位在初级体感皮层中进行了源定位。此外，对诱导 EEG 反应的参数分析表明，刺激的频率反映在非主要皮质区域中同步振荡活动的系统调制中。刺激处理伴随着与刺激频率相关的背侧枕叶皮层的 alpha 波段反应（8-12 Hz）。关键的新发现是，在整个保持间隔内，工作记忆中保持的刺激频率通过额叶前皮质的 beta 活动调制来系统地表示（20-25 Hz），该调制定位到下额回。这种在刺激保持期间的振荡活动调制与成功的频率辨别有关，因此反映了与行为相关的信息。总的来说，这些结果补充了先前在非人类灵长类动物中发现的参数工作记忆相关性的研究结果，并表明振动触觉频率在感觉记忆中的定量表示需要人类额叶皮质中同步神经活动的系统调制。
