Risto Crouse
Research Mentor(s): Alexandru Iordan
Mentor Department: Research Program on Cognition and Neuromodulation Based Interventions
Authors: Risto Crouse, Quentin Devignes, Charlene Garcia, Michael Vesia, Benjamin Hampstead, Alexandru Iordan
Session: Session 1 (9:00am – 9:50am)
Presentation Type: Poster 14
Abstract
Background – Subjective cognitive decline (SCD), characterized by self-perceived cognitive deterioration despite normal performance on objective tests, is associated with increased risk to develop Alzheimer’s disease (AD). AD’s pathophysiological processes, particularly synaptic neurodegeneration, begin years before clinical symptoms, highlighting the need for early detection strategies using measurable physiological features. Previous studies reported decreased long-term potentiation (LTP)-like cortical neuroplasticity induced by intermittent theta burst stimulation (iTBS) in individuals with dementia of Alzheimer’s type. We are among the first to investigate iTBS-induced neuroplasticity in relation to SCD. Methods – We enrolled cognitively intact older adults (N=39) who were MRI-compatible and stable on medications for at least 4 weeks. Participants completed neuropsychological assessments, including the Cognitive Change Index (CCI), a validated tool to assess self-perception of cognitive decline, and a transcranial magnetic stimulation (TMS) session that included iTBS. During the TMS session, we applied single TMS pulses to identify the brain region that controlled motor activity in the right first dorsal interosseous (FDI) muscle using a neuronavigational software and electromyographic recordings (i.e., motor-evoked potentials, MEPs). We determined the lowest stimulus intensity required to elicit a MEP of 50 µV (i.e., resting motor threshold, RMT) and the lowest intensity required to elicit a MEP of 1mV. Finally, 24 MEPs were collected (delivered at 100% of 1mV RMT) before and at several time points (5, 10, 15, 20, and 25 minutes) after a 3-minute iTBS session (delivered at 70% of RMT). We employed linear regression models to assess the relationships of total score on CCI completed by participant and informant with average MEP amplitude (expressed as a percentage of average MEP at baseline) at each timepoint after iTBS, controlling for age, sex and education. Results – There were significant positive relationships between average MEP amplitude at 5min post iTBS and total score on CCI completed by the participant (p=.041) and between average MEP amplitude at 5min (p=.011) and 15min (p=.006) post iTBS and total score on CCI completed by the informant. Conclusions – Our findings indicate that individuals with greater cognitive concerns reported by themselves or their informant exhibit a stronger early neuroplastic response to iTBS. Previous studies have reported hyperactivation at early clinical stages (i.e., mild cognitive impairment) using functional MRI. The present study extends these results to SCD and LTP-like cortical neuroplasticity. However, the relatively small sample size and reliance on self-reported measures limit generalizability. Future studies should explore the biological basis of this enhanced response and its potential predictive value for cognitive decline, incorporating neuroimaging and biomarkers to assess links to early AD pathology.
