The Modulation of Cognitive Performance with Transcranial Alternating Current Stimulation: A Systematic Review of Frequency-Specific Effects

Abstract

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows the manipulation of intrinsic brain oscillations. Numerous studies have applied tACS in the laboratory to enhance cognitive performance. With this systematic review, we aim to provide an overview of frequency-specific tACS effects on a range of cognitive functions in healthy adults. This may help to transfer stimulation protocols to real-world applications. We conducted a systematic literature search on PubMed and Cochrane databases and considered tACS studies in healthy adults (age > 18 years) that focused on cognitive performance. The search yielded n = 109 studies, of which n = 57 met the inclusion criteria. The results indicate that theta-tACS was beneficial for several cognitive functions, including working memory, executive functions, and declarative memory. Gamma-tACS enhanced performance in both auditory and visual perception but it did not change performance in tasks of executive functions. For attention, the results were less consistent but point to an improvement in performance with alpha- or gamma-tACS. We discuss these findings and point to important considerations that would precede a transfer to real-world applications.

Neurobiological After-Effects of Low Intensity Transcranial Electric Stimulation of the Human Nervous System: From Basic Mechanisms to Metaplasticity

“…Application of tACS in the clinical setting is very limited and largely implemented in the psychiatric settings ( 160 , 161 ). Accordingly, tACS was shown to successfully manipulate auditory hallucinations in schizophrenia by decoupling interhemispheric connectivity and, when administered to schizophrenic patients to the left dorsolateral prefrontal cortex and posterior parietal region in theta frequency (6 Hz), improved working memory tasks ( 162 ).…”

Electroencephalogram-Based Approaches for Driver Drowsiness Detection and Management: A Review

“…This brings another open question, that is, which frequency of the alternating current should be used. Although 6 Hz-theta frequency was used in [109,110], a more comprehensive review article about tACS pointed out that the frequency of tACS used for attention improvement is generally less consistent [111]. We suggest that future studies should take SHBP or LBP-based single-Hz EEG features into consideration, to establish the frequency parameter for tACS.…”

EEG Cross-Frequency Phase Synchronization as an Index of Memory Matching in Visual Search

“…Then subsequently, a posterior phase resetting of theta band oscillations is assumed to enable the transient cross-frequency coupling synchronization with high frequency activity in the gamma band range repeatedly found in a time window around 150 ms after target presentation. While potential alternative explanations will be discussed later, converging evidence supporting this view exists, suggesting that frontal low-frequency oscillations are indeed crucially involved in the top-down control during working memory tasks through coherence and cross-frequency interaction in fronto-parietal networks (for recent reviews, see de Vries et al, 2020; Karakaş, 2020; Klink et al, 2020; Palva & Palva, 2018).…”