Individual Differences and Long-term Consequences of tDCS-augmented Cognitive Training

Abstract

Abstract■ A great deal of interest surrounds the use of transcranial direct current stimulation (tDCS) to augment cognitive training. However, effects are inconsistent across studies, and metaanalytic evidence is mixed, especially for healthy, young adults. One major source of this inconsistency is individual differences among the participants, but these differences are rarely examined in the context of combined training/stimulation studies. In addition, it is unclear how long the effects of stimulation last, even in successful interventions. Some studies make use of follow-up assessments, but very few have measured performance more than a few months after an intervention. Here, we utilized data from a previous study of tDCS and cognitive training [Au, J., Katz, B., Buschkuehl, M., Bunarjo, K., Senger, T., Zabel, C., et al. Enhancing working memory training with transcranial direct current stimulation. Journal of Cognitive Neuroscience, 28, 1419Neuroscience, 28, -1432Neuroscience, 28, , 2016 in which participants trained on a working memory task over 7 days while receiving active or sham tDCS. A new, longer-term follow-up to assess later performance was conducted, and additional participants were added so that the sham condition was better powered. We assessed baseline cognitive ability, gender, training site, and motivation level and found significant interactions between both baseline ability and motivation with condition (active or sham) in models predicting training gain. In addition, the improvements in the active condition versus sham condition appear to be stable even as long as a year after the original intervention. ■

Multi-session Transcranial Direct Current Stimulation Over Primary Motor Cortex Facilitates Sequence Learning, Chunking, and One Year Retention

“…More recently, Au et al (2016) reported significant gains in verbal working memory after participants received tDCS over either left or right DLPFC. The same research team demonstrated that 12 months later, individuals who had initially received real tDCS, as opposed to sham, displayed substantial benefits to long-term retention (Katz et al, 2017). A possible mechanism underlying the long-term retention or relearning that we observed in both the left PFC and the M1 tDCS groups could involve plasticity-related protein synthesis.…”

The effects of different protocols of physical exercise and rest on long-term memory

“…Reasons for this variance may be due to differences in the implemented protocols, individual reactions to exercise in general, as well as differences in baseline cognitive abilities and motivation to complete the tasks (36). This perhaps highlights the need for an initial cognitive test to measure baseline performance, so comparisons between the conditions can be made.…”

Impact of 3-Day Combined Anodal Transcranial Direct Current Stimulation-Visuospatial Training on Object-Location Memory in Healthy Older Adults and Patients with Mild Cognitive Impairment

“…However, although MCI patients scored higher in BDI compared to HE, the scores did not reach the threshold for clinical depression and may accordingly differ with respect to tonic cortical activation/excitation from depressed patients resulting in a different atDCS response. Moreover, since knowledge about confounders mostly stem from single session tDCS studies, it is largely unclear if and how individual differences of several (pathological) age-related changes such as cranial anatomy, functional connectivity, excitation/inhibition balance, psychological, and cognitive status affect both, cortical excitability and cognitive training independently and/or its combination [112]. Hence, a non-trivial, complex influence of inter-individual factors in response to multi-day tDCS seems likely.…”