Neurophysiological mechanisms of transcranial alternating current stimulation

Abstract

Neuronal oscillations are the primary basis for precise temporal coordination of neuronal processing and are linked to different brain functions. Transcranial alternating current stimulation (tACS) has demonstrated promising potential in improving cognition by entraining neural oscillations. Despite positive findings in recent decades, the results obtained are sometimes rife with variance and replicability problems, and the findings translation to humans is quite challenging. A thorough understanding of the mechanisms underlying tACS is necessitated for accurate interpretation of experimental results. Animal models are useful for understanding tACS mechanisms, optimizing parameter administration, and improving rational design for broad horizons of tACS. Here, we review recent electrophysiological advances in tACS from animal models, as well as discuss some critical issues for results coordination and translation. We hope to provide an overview of neurophysiological mechanisms and recommendations for future consideration to improve its validity, specificity, and reproducibility.

Exploring the Prospects of Transcranial Electrical Stimulation (tES) as a Therapeutic Intervention for Post-Stroke Motor Recovery: A Narrative Review

“…tACS does not significantly alter the overall rate of action potentials. Instead, it modulates the timing of neuronal spikes, resulting in a phase shift in endogenous oscillations, i.e., entrainment [58,59]. The modulation effect of tACS can also be explained through the concept of the Arnold tongue, which represents a triangular relationship between stimulation frequency and amplitude.…”

Transcranial alternating current stimulation (tACS) at gamma frequency: an up-and-coming tool to modify the progression of Alzheimer’s Disease

“…Thus, in this pre-clinical frame of exploring gamma tACS in AD treatments, animal studies are still limited, likely due to the technical and methodological challenges related to electrode implantation, duration of the treatment protocol and intensity of the current delivery. Moreover, there are concerns about translational compatibility of tACS results across species and techniques [ 110 ]. Indeed, in a translational comparison, the correlation between animal findings and humans should be carefully run [ 51 ].…”

Would frontal midline theta indicate cognitive changes induced by non-invasive brain stimulation? A mini review

“…Regarding TMS, long-lasting therapeutic effects seem to be related to LTP (longterm potentiation) and LTD (long-term depression) involving post-synaptic NMDA receptors, changing BDNF production in stimulated and remote brain regions, but increased, unchanged, or decreased in the serum and cerebrospinal fluid (Chervyakov et al, 2015;Lefaucheur, 2019). There is also evidence that tACS may also induce plasticity mediated by NMDA receptors in the motor cortex, because the after-effects of 20 Hz tACS was suppressed by a NMDA antagonist (Wischnewski et al, 2019(Wischnewski et al, , 2023 and may potentially induce BDNF changes (He et al, 2023).…”