Alpha oscillatory activity is causally linked to working memory retention

Abstract

Although previous studies have reported correlations between alpha oscillations and the “retention” subprocess of working memory (WM), causal evidence has been limited in human neuroscience due to the lack of delicate modulation of human brain oscillations. Conventional transcranial alternating current stimulation (tACS) is not suitable for demonstrating the causal evidence for parietal alpha oscillations in WM retention because of its inability to modulate brain oscillations within a short period (i.e., the retention subprocess). Here, we developed an online phase-corrected tACS system capable of precisely correcting for the phase differences between tACS and concurrent endogenous oscillations. This system permits the modulation of brain oscillations at the target stimulation frequency within a short stimulation period and is here applied to empirically demonstrate that parietal alpha oscillations causally relate to WM retention. Our experimental design included both in-phase and anti-phase alpha-tACS applied to participants during the retention subprocess of a modified Sternberg paradigm. Compared to in-phase alpha-tACS, anti-phase alpha-tACS decreased both WM performance and alpha activity. These findings strongly support a causal link between alpha oscillations and WM retention and illustrate the broad application prospects of phase-corrected tACS.

Transcranial alternating current stimulation for the treatment of major depressive disorder: from basic mechanisms toward clinical applications

“…A recent modeling study suggested that TI can affect the human hippocampus ( Lee et al, 2020 ), and an investing study claimed that TI could be safe and well tolerated in human participants ( Piao et al, 2022 ). The other development is closed-loop tACS, which has significant potential for treating neurological and psychiatric disorders with irregular patterns ( Chen et al, 2023 ). Recent studies have indicated that the effect of tACS is influenced by the state of the ongoing brain oscillations ( Krause et al, 2022 ).…”

Working memory enhancement using real-time phase-tuned transcranial alternating current stimulation

“…The con�nuous phase-tuning in our approach naturally results in a con�nuous frequency-tuning, as a constant phase difference between two signals implies that they have iden�cal frequency [41]. transform was applied to the data to remove broadband s�mula�on ar�facts and obtain a real-�me phase es�mate of parieto-occipital alpha oscilla�ons (8)(9)(10)(11)(12)(13)(14). (E) The real-�me phase es�mate of alpha oscilla�ons was incremented by φ to obtain the phase of the CLAM-tACS envelope signal.…”

Alpha Traveling Waves during Working Memory: Disentangling Bottom-up Gating and Top-down Gain Control

“…Yet, several studies have also demonstrated a connection between alpha waves and working memory. For example, alpha oscillations were persistently observed during working memory retention (see Roux & Uhlhaas, 2014 for review), and causally linked to this process (Chen et al, 2023; Riddle et al, 2020; Sauseng et al, 2009). Moreover, experimental findings revealed that alpha power increased with working memory load (Jensen et al, 2002) and with anticipated distractors (Bonnefond & Jensen, 2012; Payne et al, 2013), suggesting that alpha oscillations may be involved in protecting memory maintenance through an inhibitory mechanism.…”