Can accelerated transcranial direct current stimulation improve memory functions? An experimental, placebo-controlled study

Abstract

The aim of this study was to investigate whether transcranial Direct Current Stimulation (tDCS) could improve verbal memory functions in healthy old and younger participants. We hypothesized that active tDCS led to significantly improved memory function, compared to placebo tDCS. Forty healthy participants (20 old and 20 younger participants) were included in the study. We applied a novel stimulation protocol, where six sessions of anodal tDCS were administrated during two consecutive days. Each tDCS session lasted 30 min. The current intensity was 2mA and the stimulation area was the left temporal lobe at T3 in the 10–20 EEG system. Immediate recall, delayed recall and recognition memory were assessed with California Verbal Learning Test II (CVLT-II) and executive functions were assessed with the Trail Making Test (TMT) before the first tDCS session and after the last tDCS session. Half of the participants received placebo tDCS, whereas the other half received active tDCS. We did not reveal any significant differences between active and placebo tDCS in memory functions. However, there was a significant difference between active and placebo tDCS in executive function measured by the Trail Making Test (TMT). This experimental study failed to reveal significant differences between active and placebo accelerated tDCS for verbal memory functions. However, accelerated tDCS was found to be well-tolerated in this study.

tDCS over the left prefrontal Cortex improves mental flexibility and inhibition in geriatric inpatients with symptoms of depression or anxiety: A pilot randomized controlled trial

“…In a similar study design targeting Parkinson's Disease, Doruk and colleagues ( 66 ) report significant improvements on the TMT-B without changes on the TMT-A, with the maintenance of these findings extending to one-month post-stimulation. Bystad and colleagues ( 67 ) further report significant gains on the TMT-B without improvements in the TMT-A only within a young adult group. In addition, Loftus and colleagues ( 68 ) report reaction time improvements on the Stroop task in young adults after receiving anodal DLPFC stimulation resulting in inhibitory control enhancement; our results continue to support inhibition control enhancement in older aged adults.…”

A Literature Mini-Review of Transcranial Direct Current Stimulation in Schizophrenia

“…Previously published studies indicate that short repetition interval (<30 min) can lead to prolongation of tDCS after-effects ( 81 – 83 ), whereas longer repetition interval (3 or 24 h) result in no excitability-enhancing after effects or can nullify them ( 83 , 84 ). Current research focuses on accelerated tDCS protocols ( 85 , 86 ), and future RCT protocols using tDCS as a treatment option for schizophrenia might benefit from their implementation.…”

Moving to accelerated protocols of tDCS in schizophrenia: A case report

“…For instance, Monte-Silva et al reported that spacing two tDCS sessions by short intervals of 3 and 20 minutes resulted in long-lasting effects of tDCS on motor cortical excitability with a greater magnitude of effects for the 20-min interval [4], whereas longer intervals, such as 3 or 24 hours, abolished the long-lasting effects of tDCS [4,5]. Thus, the use of short intervals between sessions (<30 min) has been proposed to prolong the effect of tDCS [6]. The clinical potential of such protocols, which can be referred to as "accelerated" or "intensive", is increasingly being investigated with other forms of noninvasive brain stimulation.…”