The effect of transcranial direct current stimulation concurrent with cognitive training on working memory

Hu, Rong (2024). The effect of transcranial direct current stimulation concurrent with cognitive training on working memory. University of Birmingham. Ph.D.

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Abstract

Background
Working memory plays a crucial role in higher-level cognitive functions such as reasoning, learning, and comprehension. It also serves as a predictor of academic achievement and professional success in individuals. However, working memory may decline with ageing and/or acquired brain injury, including strokes. Cognitive training can counteract cognitive decline, particularly when complemented with Transcranial Direct Current Stimulation (tDCS). TDCS can modulate neural excitability and enhance neuroplasticity, making it a promising tool for enhancing working memory when combined with working memory training. Nevertheless, the efficacy of tDCS combined with working memory training may vary among healthy adults and the elderly, with limited research focusing on acute stroke patients.
Method
In this project, I leverage between-participant designs to investigate the efficacy of combined tDCS and working memory training intervention for modulating working memory function in three distinct groups: healthy adults, elderly participants, and acute stroke patients. The initial phase of the project aims to explore the impact of various factors, such as the choice of tDCS setup (high-definition tDCS vs. bipolar tDCS), the experimental protocol (online vs. offline tDCS), and external variables (e.g., age, initial working memory capacity, and cognitive strategy), on the outcomes of the intervention. To achieve this, I administered one or more sessions of 2mA tDCS for 20 minutes along with a working memory task (specifically, the nBack task), simultaneously engaging both the storage and processing components of working memory. In the project’s second phase, I applied the insights gained from the initial phase to design an intervention specifically tailored for a group of acute stroke patients.
Results
In healthy young adults, I found that the application of a single-session high-definition tDCS, either online or offline with a working memory task, did not have a significant impact on performance. However, when bipolar tDCS was utilized, and individual differences were considered, there was a significant benefit for young adults with lower working memory capacity. This trend was also evident in older adults, where I observed that an individual’s initial working memory capacity played a pivotal role in the effectiveness of a combination of tDCS and working memory training over a short period.
Building upon these findings, I proceeded to investigate this specific setup, involving 20 minutes of anodal bipolar tDCS over the right dorsolateral prefrontal cortex, along with adaptive working memory training, in acute stroke patients, showing a working memory decline. In this context, I found that stroke patients with left-sided brain lesions exhibited notable improvements in working memory performance.
Conclusion
In summary, this comprehensive study underscores the notion that tDCS functions as a “state-dependent” intervention, showing discernible benefits for specific groups: healthy young adults with initially low working memory capacity who were given external strategy support, elderly individuals who are both older and have a low baseline working memory, and acute stroke patients with left-sided brain lesions. In the future, researchers should carefully take these factors into account and delve into the mechanisms underpinning the effectiveness of this intervention.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):