Effectiveness of a Non-Invasive, Low-Intensity Brain Stimulation Approach in Addressing Emotional Regulation (BEEM Study)

Research background

Older adults with mild cognitive impairment (MCI) can often experience changes in their emotions and behavior that co-occur with cognitive and functional decline. These changes can worsen an individual’s cognitive capacity and risk of progression to Alzheimer’s disease (AD), as well as subject both the individual and the individual’s family members to additional distress. Emotional and behavioral symptoms can vary within and across individuals; however, our understanding of the potentially shared neural mechanisms that may underly these symptoms is quite limited.

Our lab has previously identified a functional (i.e. task-related) brain network common to MCI and AD patients who have co-existing symptoms that is significantly related to the Neuropsychiatric Inventory Questionnaire (NPI-Q, a measure of emotional and behavioral symptoms in dementia) and AD pathology (specifically the amyloid-beta-to-tau ratio in cerebrospinal fluid).

Interestingly, we found that emotional and behavioral symptoms are related to a shared network involving a subset of frontal, temporal, and subcortical brain regions. Additionally, the relationships between these regions’ activity over a given amount of time (known as functional connectivity) varied for different symptoms. One of our aims going forward is to further explore these differences in functional connectivity and better understand how they can be modulated as a form of cognitive intervention to help improve the emotional and behavioral health of individuals who may be at risk for developing AD.

Regions in the shared neural network whose functional connectivity is related to emotional and behavioral symptoms common in individuals with MCI and AD.

Figure from Wang X et al, 2019. Identify a shared neural circuit linking multiple neuropsychiatric symptoms with Alzheimer’s pathology. Brain Imaging Behav 13(1):53-64. DOI: 10.1007/s11682-017-9767-y

Research aims

Based on our preliminary evidence, we are conducting a study to further explore the mechanisms underlying the shared brain network using a technique called transcranial direct current stimulation (tDCS). Extending our previous findings will help us determine the effect of tDCS on the symptom-shared network, as well as the relationship between this network and subjects’ partner-rated symptoms, so that we can identify therapeutic targets in the brain that respond well to interventions (such as tDCS).  

Intervention

The intervention involves a brain stimulation (or neuromodulation) technique called transcranial direct current stimulation (tDCS). We are able to use tDCS to stimulate brain regions temporarily based on the regions we are interested in studying, enabling us to study the brain non-invasively and painlessly. The tDCS device supplies a constant, low electrical current between two electrodes (sponges lightly soaked in saline water) that rest on top of the head over the brain region of interest. However, any tDCS-induced changes in brain activity are temporary and will return to baseline after the session ends.

An example of a Multiple Object Tracking (MOT) task. Multiple moving objects are displayed on the computer screen, with a subset of objects different from the other objects. Participants track the dark objects as they move and try to continue tracking their locations after they switch to the yellow objects. After several seconds, the objects stop moving and one of the objects is replaced with a visual cue, prompting the participant to determine whether the cued object was one of the dark objects in the subset at the beginning.