Theta-alpha cross-frequency synchronization facilitates working memory control – a modeling study

Abstract

Despite decades of research, the neural mechanism of central executive and working memory is still unclear. In this paper, we propose a new neural network model for the real-time control of working memory. The key idea is to consider separately the role of neural activation from that of oscillatory phase. Neural populations encoding different information would not confuse each other when the populations have different oscillatory phases. Depending on the current situation, relevant memories bind together through phase-locking between theta-frequency oscillation of a Central Unit and alpha-frequency oscillations of the relevant group of Memory Units. The Central Unit dynamically controls which Memory Units should be synchronized (and the encoded memory would be processed), and which units should be out of phase (the encoded memory is standby and would not be processed yet). Simulations of two working memory tasks are provided as examples. The model is in agreement with many recent experimental results of human scalp EEG analysis, which reported observations of neural synchronization and cross-frequency coupling during working memory tasks. This model offers a possible explanation of the underlying mechanism for these experiments.

Tracking Transient Changes in the Neural Frequency Architecture: Harmonic Relationships between Theta and Alpha Peaks Facilitate Cognitive Performance

“…These results are in line with previous evidence pointing to the importance of alpha-theta interactions in tasks requiring working memory and executive control (Kawasaki et al, 2010;Dimitriadis et al, 2016;Akiyama et al, 2017;Popov et al, 2018). In this respect, it has been suggested that alpha oscillations subserve short-term maintenance of information (Kawasaki et al, 2010;Chik, 2013;Akiyama et al, 2017) as well as reactivation of semantic knowledge (Klimesch et al, 1999), whereas theta oscillations underlie executive control (Schack et al, 2005;Lisman and Jensen, 2013). Based on our results, we propose that the integration between cognitive functions encompassed in alpha and theta rhythms is facilitated through 2:1 harmonic relationships, as this frequency arrangement would enable cross-frequency (phase) synchronization (and therefore information transmission; Fries, 2005Fries, , 2015 to occur between their underlying neural networks.…”

From thoughtless awareness to effortful cognition: alpha - theta cross-frequency dynamics in experienced meditators during meditation, rest and arithmetic

“…Based on our results and previous literature, we speculate that when cognitive demands increase, alpha and theta rhythms separate from each other in the frequency spectrum (alpha accelerates, theta decelerates) to exert their respective functions (i.e. upper alpha = retrieval and storage information; lower theta = manipulation of information 18,19,22 , while, at the same time, allowing their interaction by the formation of transient harmonic relationships (i.e. enabling cross-frequency phase synchronization for short periods) 30,32 .…”

From thoughtless awareness to effortful cognition: alpha - theta cross-frequency dynamics in experienced meditators during meditation, rest and arithmetic

“…Based on our results and previous literature, we speculate that when cognitive demands increase, alpha and theta rhythms separate from each other in the frequency spectrum (alpha accelerates, theta decelerates) to exert their respective functions (i.e. upper alpha = retrieval and storage information; lower theta = manipulation of information 18,19,22 , while allowing their interaction by the formation of transient harmonic relationships (i.e. enabling cross-frequency phase synchronization for short periods) 30,32 .…”