Speaker
Description
Previous research has demonstrated that transcranial direct current stimulation (tDCS) is a promising, non-invasive intervention for Alzheimer’s disease and related dementias (ADRD). tDCS modulates cortical excitability of underlying brain regions via primary effects on excitatory neurotransmitters such as glutamate (Glu). Neuroimaging studies have reported varying levels of Glu and amyloid ꞵ production in ADRD. Furthermore, technological advances in proton functional MR spectroscopy (H fMRS) have enabled in vivo tracking of Glu levels during task performance, therefore revealing the critical role of Glu in learning and memory. However, the link between Glu levels and brain activity and how tDCS influences this relationship within an aging population is unknown. Here, we tested healthy older adults on an ecologically relevant association memory task to examine if high-definition tDCS (HD-tDCS) influences the dynamics of Glu during task performance. To compare the effects of stimulation, we conducted a double-blind study in which participants completed the object-location association task (OLA) twice (pre and post-stimulation) in the scanner. In addition, we collected fNIRS resting state activity in parallel with active or sham HD-tDCS where participants underwent 8 minutes of baseline and 20 minutes of stimulation. Our montage targeted the left LPFC region as it was previously established to be engaged during the OLA paradigm. Preliminary H fMRS results suggest a greater concentration of Glu after active compared to sham stimulation. In addition, correlations between Glu and the electrical field at the brain level indicate that a stronger electrical field during stimulation was associated with higher Glu concentrations.
Keywords: Cognitive Aging, HD-tDCS, fMRS, tDCS
