Why does brain stimulation combined with adaptive working memory training lead improve cognition?

Funding Round: 3 2015-2017

Research Question: Why does brain stimulation combined with adaptive working memory training lead to improved cognition?

Interdisciplinary Approach: This project combines theories of cognitive neural systems from a reverse-engineering perspective with a novel combination of electrical brain stimulation and a behavioral intervention to improve cognition and neural efficiency.   

Potential Implications of Research: The results will inform the design of interventions aimed at improving cognitive performance and learning.

Working memory (WM) is a limited-capacity mental workspace that is used to actively maintain and manipulate information in the mind.  Performance on tests of working memory is highly correlated with IQ and educational learning success. The link between WM performance and learning success appears to be driven by the ability to selectively enhance relevant information and suppress irrelevant information, and to organize the relevant information into efficient “chunks”.  However, the processes of enhancing and suppressing information are effortful and fatiguing.  This is particularly true for individuals who have suffered brain injury or disease such as Multiple Sclerosis (MS).  Indeed WM deficits are common in a number of patient population, including those with MS. Although not always successful or transferable, recent research has found that working memory can be improved in healthy adults through training and brain stimulation.  For example, when Transcranial Direct Current Stimulation (tDCS), a safe form of non-invasive brain stimulation, is applied to regions known to be important for selecting and suppressing information (the dorsolateral prefrontal cortex), researchers have found temporary improvement in WM performance in both healthy adults and those with cognitive impairments.

In this project, we will tax working memory brain networks in individuals with MS through a dual approach. First, we will first bring neurons in the dorsolateral prefrontal cortex closer to firing threshold via tDCS. Then, while working memory networks are enhanced, participants will receive WM training that continuously adapts to their performance, and that remains equally engaging and demanding throughout the training. We hypothesize that this dual approach, combing both brain stimulation and training, will improve working memory by reducing the “effort” needed to initiate and maintain the selection and suppression processes.  If so, we expect to find improved cognitive performance and less mental fatigue on a battery of cognitive tests and self-report questionnaires. We will also use fMRI, a type of neuroimaging procedure, to examine whether our intervention results in changes in the connectivity within working memory networks, less fMRI activation (indicating less metabolic demand, or neural “effort”) for the same level of performance, and correlations between neuroimaging changes and cognitive fatigue measures.

This project offers a novel approach to improving WM by combining tDCS with training that continuously adapts to the performance of the individual.. If successful, this approach could lead to improvements in other cognitive functions as well as increased ease and speed of learning in multiple contexts (e.g. educational and occupational settings). Ultimately, this approach could prove helpful for a variety of populations suffering from WM deficits including those with brain injury, cancer, or learning difficulties. 

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