Harvard Medical School - Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA.
Massachusetts Mental Health Center Public Psychiatry Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
Neuroimage. 2017 Nov 1;161:1-8. doi: 10.1016/j.neuroimage.2017.08.040. Epub 2017 Aug 14.
Auditory working memory (WM) processing in everyday acoustic environments depends on our ability to maintain relevant information online in our minds, and to suppress interference caused by competing incoming stimuli. A challenge in communication settings is that the relevant content and irrelevant inputs may emanate from a common source, such as a talkative conversationalist. An open question is how the WM system deals with such interference. Will the distracters become inadvertently filtered before processing for meaning because the primary WM operations deplete all available processing resources? Or are they suppressed post perceptually, through an active control process? We tested these alternative hypotheses by measuring magnetoencephalography (MEG), EEG, and functional MRI (fMRI) during a phonetic auditory continuous performance task. Contextual WM maintenance load was manipulated by adjusting the number of "filler" letter sounds in-between cue and target letter sounds. Trial-to-trial variability of pre- and post-stimulus activations in fMRI-informed cortical MEG/EEG estimates was analyzed within and across 14 subjects using generalized linear mixed effect (GLME) models. High contextual WM maintenance load suppressed left auditory cortex (AC) activations around 250-300 ms after the onset of irrelevant phonetic sounds. This effect coincided with increased 10-14 Hz alpha-range oscillatory functional connectivity between the left dorsolateral prefrontal cortex (DLPFC) and left AC. Suppression of AC responses to irrelevant sounds during active maintenance of the task context also correlated with increased pre-stimulus 7-15 Hz alpha power. Our results suggest that under high auditory WM load, irrelevant sounds are suppressed through a "late" active suppression mechanism, which prevents short-term consolidation of irrelevant information without affecting the initial screening of potentially meaningful stimuli. The results also suggest that AC alpha oscillations play an inhibitory role during auditory WM processing.
听觉工作记忆（WM）处理日常声学环境取决于我们的能力，以保持相关信息在线在我们的脑海中，并抑制由竞争传入刺激引起的干扰。在通信环境中的一个挑战是，相关的内容和无关的输入可能来自于同一个来源，如健谈的对话者。一个悬而未决的问题是 WM 系统如何处理这种干扰。分心者是否会在处理意义之前被无意中过滤掉，因为主要的 WM 操作耗尽了所有可用的处理资源？或者它们是在感知后通过主动控制过程被抑制的？我们通过在语音听觉连续表现任务期间测量脑磁图（MEG）、脑电图（EEG）和功能磁共振成像（fMRI）来测试这些替代假设。通过调整 cue 和目标字母声音之间的“填充”字母声音的数量来操纵上下文 WM 维护负载。使用广义线性混合效应（GLME）模型，在 14 名受试者内和跨受试者分析 fMRI 知情皮质 MEG/EEG 估计的刺激前和刺激后激活的trial-to-trial 变异性。高语境 WM 维护负载抑制了无关语音声音出现后约 250-300 毫秒时的左听觉皮层（AC）激活。这种效应与左背外侧前额叶皮层（DLPFC）和左 AC 之间的 10-14 Hz 阿尔法范围振荡功能连接增加相吻合。在主动维护任务上下文期间，对无关声音的 AC 反应的抑制也与刺激前 7-15 Hz 阿尔法功率增加相关。我们的结果表明，在高听觉 WM 负载下，无关声音通过“晚期”主动抑制机制被抑制，该机制阻止了无关信息的短期巩固，而不影响潜在有意义刺激的初始筛选。结果还表明，AC 阿尔法振荡在听觉 WM 处理过程中发挥抑制作用。
