Event-Related Potentials as Markers of Efficacy for Combined Working Memory Training and Transcranial Direct Current Stimulation Regimens: A Proof-of-Concept Study

Abstract

Our brains are often under pressure to process a continuous flow of information in a short time, therefore facing a constantly increasing demand for cognitive resources. Recent studies have highlighted that a lasting improvement of cognitive functions may be achieved by exploiting plasticity, i.e., the brain’s ability to adapt to the ever-changing cognitive demands imposed by the environment. Transcranial direct current stimulation (tDCS), when combined with cognitive training, can promote plasticity, amplify training gains and their maintenance over time. The availability of low-cost wearable devices has made these approaches more feasible, albeit the effectiveness of combined training regimens is still unclear. To quantify the effectiveness of such protocols, many researchers have focused on behavioral measures such as accuracy or reaction time. These variables only return a global, non-specific picture of the underlying cognitive process. Electrophysiology instead has the finer grained resolution required to shed new light on the time course of the events underpinning processes critical to cognitive control, and if and how these processes are modulated by concurrent tDCS. To the best of our knowledge, research in this direction is still very limited. We investigate the electrophysiological correlates of combined 3-day working memory training and non-invasive brain stimulation in young adults. We focus on event-related potentials (ERPs), instead of other features such as oscillations or connectivity, because components can be measured on as little as one electrode. ERP components are, therefore, well suited for use with home devices, usually equipped with a limited number of recording channels. We consider short-, mid-, and long-latency components typically elicited by working memory tasks and assess if and how the amplitude of these components are modulated by the combined training regimen. We found no significant effects of tDCS either behaviorally or in brain activity, as measured by ERPs. We concluded that either tDCS was ineffective (because of the specific protocol or the sample under consideration, i.e., young adults) or brain-related changes, if present, were too subtle. Therefore, we suggest that other measures of brain activity may be more appropriate/sensitive to training- and/or tDCS-induced modulations, such as network connectivity, especially in young adults.

The efficacy of combining cognitive training and noninvasive brain stimulation: A transdiagnostic systematic review and meta-analysis.

“…In all other studies, either a research assistant or study technician ( k = 4; 6%) administered the training, or it was not mentioned by whom the training was administered ( k = 61; 85%, categorized as “computerized” for the analyses). Five studies (7%) reported the use of cognitive strategies (Assecondi et al, 2022; Chapman, n.d.; Cotelli et al, 2014; Das et al, 2019; Martin et al, 2019). One study reported that the training was given in a group setting (Das et al, 2019; note that this study was one of six outliers for the cognitive outcome domain of executive functioning).…”

Lasting Enhancements in Neural Efficiency by Multi-session Transcranial Direct Current Stimulation in Working Memory Training

“…A recent study utilizing resting-state functional magnetic resonance imaging (fMRI) found improved brain network processing efficiency with 3-day of tDCS+WMT one day after training [40]. However, no significant effects of tDCS on brain activity were found in a 3day WMT+tDCS study that quantified long-term neurobehavioral effects using ERPs at one month [38]. Therefore, it remains an open question whether the cumulative effects of tDCS during WMT can produce lasting effects on the functional reorganization of cortical neural activity, which can be revealed by task-related EEG measures long-term after the end of training.…”

Neurophysiological correlates of short-term recognition of sounds: Insights from magnetoencephalography

“…Pairing these types of studies with neuroscientific techniques which possess fine-grained temporal resolution like EEG and MEG, exposes unique fast-scale neural responses occurring in response to standard and discrepant stimuli (Hillebrand et al, 2018). In fact, M/EEG measurements reveal an array of contiguous automatic event-related potentials/fields (ERP/Fs) categorized into three main classes based on their latencies (Assecondi, Villa-Sánchez & Shapiro, 2022). When contextualising their succession and distinct topographies in relation to PC, it becomes evident that auditory information processing provokes spatially distributed neural responses which cross neural hierarchies at distinct processing stages.…”