Alterations in oscillatory cortical activity indicate changes in mnemonic processing during continuous item recognition
Alterations in oscillatory cortical activity indicate changes in mnemonic processing during continuous item recognition
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DOI：
10.1007/s00221-018-5439-4
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发表时间：
2019-02-01
影响因子：
2
通讯作者：
Gruber, Thomas
中科院分区：
文献类型：
--
作者：
Graetz, Sebastian;Daume, Jonathan;Gruber, Thomas
将重复刺激分类为新旧是日常感知的一般机制。然而，这一过程背后的皮层机制尚不完全清楚。一般来说，记忆过程被认为依赖于几个频率的振荡大脑活动的变化以及它们之间的相互作用。较低频率，主要是θ波段（3-7赫兹）和α波段（8-14赫兹）活动，分别归因于行政控制和资源管理；而最近的研究显示，更高的频率，例如伽马波段（>25赫兹）的活动，反映了皮层物体表征的激活。此外，低频相位到高频振幅耦合（PAC）最近被发现协调相关的助记网络。为了进一步揭示重复呈现刺激背后的记忆过程，我们在记录高密度脑电图的同时，应用了一个连续的项目识别任务，每个项目最多有五次呈现（重复之间的平均时间类似于10秒）。我们检查了频谱振幅调制以及PAC。我们观察到theta振幅在第二次呈现时达到峰值，第二次呈现后α抑制减少，响应时间减少，以及第三次呈现后额叶部位的theta-gamma PAC（3至7至-30至45 Hz）减少。我们总结了从显式到内隐式的助记处理的转变，发生在第三次呈现时，theta功率表示基于重复的情景信息编码，PAC作为局部神经网络协调的神经关联。
The classification of repeating stimuli as either old or new is a general mechanism of everyday perception. However, the cortical mechanisms underlying this process are not fully understood. In general, mnemonic processes are thought to rely on changes in oscillatory brain activity across several frequencies as well as their interaction. Lower frequencies, mainly theta-band (3-7 Hz) and alpha-band (8-14 Hz) activity, are attributed to executive control and resource management, respectively; whereas recent studies revealed higher frequencies, e.g. gamma-band (>25 Hz) activity, to reflect the activation of cortical object representations. Furthermore, low-frequency phase to high-frequency amplitude coupling (PAC) was recently found to coordinate the involved mnemonic networks. To further unravel the processes behind memorization of repeatedly presented stimuli, we applied a continuous item recognition task with up to five presentations per item (mean time between repetitions similar to 10 s) while recording high-density EEG. We examined spectral amplitude modulations as well as PAC. We observed theta amplitudes reaching a peak at second presentation, a reduction of alpha suppression after second presentation, decreased response time, as well as reduced theta-gamma PAC (3 to 7 to -30 to 45 Hz) at frontal sites after third presentation. We conclude a shift from an explicit- to an implicit-like mnemonic processing, occurring around third presentation, with theta power to signify encoding of repetition-based episodic information and PAC as a neural correlate of the coordination of local neural networks.