Department of Psychology, University of Konstanz, Postfach ZPR, 78457 Konstanz, Germany.
Neuropsychologia. 2012 Dec;50(14):3519-27. doi: 10.1016/j.neuropsychologia.2012.08.023. Epub 2012 Sep 10.
The thalamus is believed to be a key node in human memory networks, however, very little is known about its real-time functional role. Here we examined the dynamics of thalamocortical communication during long-term episodic memory retrieval in two experiments. In experiment 1, intrathalamic and surface EEG was recorded in an epileptic patient implanted with depth electrodes for brain stimulation therapy. In a recognition memory test, early (300-500 ms) stimulus-linked oscillatory synchrony between mediodorsal thalamic and frontal surface electrodes at beta frequency (20 Hz) was enhanced for correctly remembered old compared to correctly rejected new items. Directionality measures (Granger causality) indicated that the thalamus was the sender, and the neocortex the receiver, of this beta signal, which also modulated the power of neocortical gamma (55-80 Hz) oscillations (cross-frequency coupling). Experiment 2 validated the cross-frequency coupling effects in a healthy participant sample. Confirming the findings from experiment 1, significantly increased cross-frequency coupling was found over frontal scalp electrodes during successful recognition. Extending anatomical knowledge on thalamic connectivity with frontal neocortex, these results suggest that the thalamus sends an early memory signal to frontal regions, triggering further memory search processes.
丘脑被认为是人类记忆网络中的一个关键节点，但人们对其实时功能作用知之甚少。在这里，我们在两项实验中研究了长期情景记忆检索过程中丘脑皮质通讯的动力学。在实验 1 中，对一名植入深部电极以进行脑刺激治疗的癫痫患者进行了颅内和表面 EEG 记录。在识别记忆测试中，与正确拒绝的新项目相比，正确记住的旧项目在中背侧丘脑和额表面电极之间以β频率（20 Hz）出现的早期（300-500 ms）与刺激相关的振荡同步性增强。方向度量（格兰杰因果关系）表明，β信号的发送者是丘脑，接收者是新皮层，该信号还调制了新皮层γ（55-80 Hz）振荡（交叉频耦合）的功率。实验 2 在健康参与者样本中验证了这种交叉频耦合效应。与实验 1 的结果一致，在成功识别过程中，在前额头皮电极上发现了明显增加的交叉频耦合。这些结果扩展了与额叶新皮层的丘脑连接的解剖学知识，表明丘脑向额叶区域发送早期记忆信号，触发进一步的记忆搜索过程。
