Transcranial Direct Current Stimulation (tDCS) for Memory Enhancement

Abstract

Memory enhancement is one of the great challenges in cognitive neuroscience and neurorehabilitation. Among various techniques used for memory enhancement, transcranial direct current stimulation (tDCS) is emerging as an especially promising tool for improvement of memory functions in a non-invasive manner. Here, we present a tDCS protocol that can be applied for memory enhancement in healthy-participant studies as well as in aging and dementia research. The protocol uses weak constant anodal current to stimulate cortical targets within cortico-hippocampal functional network engaged in memory processes. The target electrode is placed either on the posterior parietal cortex (PPC) or the dorsolateral prefrontal cortex (DLPFC), while the return electrode is placed extracranially (i.e., on the contralateral cheek). In addition, we outline a more advanced method of oscillatory tDCS, mimicking a natural brain rhythm to promote hippocampus-dependent memory functions, which can be applied in a personalized and non-personalized manner. We present illustrative results of associative and working memory improvement following single tDCS sessions (20 minutes) in which the described electrode montages were used with current intensities between 1.5 mA and 1.8 mA. Finally, we discuss crucial steps in the protocol and methodological decisions that must be made when designing a tDCS study on memory.

Efficacy and Safety of Transcranial Electric Stimulation during the Perinatal Period: A Systematic Literature Review and Three Case Reports

“…This study did not show the superiority of tDCS in reducing depression scales, but the rate of remission in the postpartum period was higher in the tDCS group than in the placebo group. These results are encouraging and should incite researchers to carry out other RCT on the subject, especially as the interpretation of Vigod et al’s results is limited by the low power of the study, with a number of subjects that is probably too small to evaluate the effectiveness of tDCS [ 65 ].…”

Feasibility of Combining Transcranial Direct Current Stimulation and Active Fully Embodied Virtual Reality for Visual Height Intolerance: A Double-Blind Randomized Controlled Study

“…At the methodological level, it is important to consider this work as an initial experiment to understand the effect sizes for this specific design and keep in mind that in general, a between-subject design requires at least between 30 and 40 subjects in tDCS studies [62]. The small size effect (0.1 for the SUD criteria at V4) indicates that the combined VR-tDCS stimulation paradigm must be improved with fundamental studies before the hypothesis of a 0.4-0.5 effect size can be reached.…”

Blinding in tDCS Studies: Correct End-of-Study Guess Does Not Moderate the Effects on Associative and Working Memory

“…To estimate whether blinding was successful, researchers typically adopt the end-of-study guess approach, when participants in both active and control groups are asked to guess if they have received the active or sham stimulation after the session [ 34 ] or, in crossover designs, to try to guess in which session they have received the sham stimulation [ 44 ]. Utilization of the end-of-study guess to assess the successfulness of blinding is a frequent approach in tDCS studies [ 28 , 32 , 33 , 45 , 46 , 47 ].…”