Repetitive Transcranial Magnetic Stimulation (rTMS) in Mild Cognitive Impairment: Effects on Cognitive Functions—A Systematic Review

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique also used as a non-pharmacological intervention against cognitive impairment. The purpose of the present review was to summarize what is currently known about the effectiveness of rTMS intervention on different cognitive domains in patients with mild cognitive impairment (MCI) and to address potential neuromodulation approaches in combination with electroencephalography (EEG) and neuroimaging, especially functional magnetic resonance imaging (fMRI). In this systematic review, we consulted three main databases (PubMed, Science Direct, and Scopus), and Google Scholar was selected for the gray literature search. The PRISMA flowchart drove the studies’ inclusion. The selection process ensured that only high-quality studies were included; after removing duplicate papers, explicit ratings were given based on the quality classification as high (A), moderate (B), or low (C), considering factors such as risks of bias, inaccuracies, inconsistencies, lack of direction, and publication bias. Seven full-text articles fulfilled the stated inclusion, reporting five double-blind, randomized, sham-controlled studies, a case study, and a randomized crossover trial. The results of the reviewed studies suggested that rTMS in MCI patients is safe and effective for enhancing cognitive functions, thus making it a potential therapeutic approach for MCI patients. Changes in functional connectivity within the default mode network (DMN) after targeted rTMS could represent a valuable indicator of treatment response. Finally, high-frequency rTMS over the dorsolateral prefrontal cortex (DLPFC) has been shown to significantly enhance cognitive functions, such as executive performance, together with the increase of functional connectivity within frontoparietal networks. The main limitations were the number of included studies and the exclusion of studies using intermittent theta-burst stimulation, used in studies on Alzheimer’s disease. Therefore, neuroimaging techniques in combination with rTMS have been shown to be useful for future network-based, fMRI-guided therapeutic approaches.

Effects of scalp acupuncture combined with repetitive transcranial magnetic stimulation on post-stroke cognitive impairment at different time intervals

“…High-frequency transcranial magnetic stimulation (HF-TMS) stimulates neuroplastic changes by increasing calcium levels, upregulating AMPA receptors, and inducing long-term potentiation (LTP), which enhances cortical excitability and can improve cognitive function when targeted at specific areas like the left dorsolateral prefrontal cortex (DLPFC) [29,30]. On the other hand, low-frequency TMS (LF-TMS) tends to decrease calcium concentration, downregulate AMPA receptors, and induce long-term depression (LTD), thereby reducing cortical excitability [31,32]. This reduction in excitability has been associated with improvement in certain cognitive domains, particularly memory, speech, attention, and executive function.…”

Repetitive transcranial magnetic stimulation impacts the executive function of patients with vascular cognitive impairment: a systematic review and meta-analysis

“…Currently, RCT stimulation sites are mostly limited to the DLPFC, but stimulating the M1 area has been demonstrated to effectively enhance cognitive capabilities. Experiments involving rTMS stimulation of the bilateral DLPFC have yielded favorable outcomes ( 81 ). Diseases are characterized by damage to multiple networks and stimulation of other regions may also cause cognitive enhancement ( 82 ).…”