The aim of this study is to determine whether non-invasive vagus nerve stimulation enhances memory formation in cognitively healthy older adults and whether the effects of stimulation depend on gut and brain health.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
150
Non-invasive vagus nerve stimulation will be delivered with a well-validated device. taVNS delivers stimulation on the left ear, with the placement of the stimulating electrode differing between the active and sham conditions. Stimulation will occur during each learning trial (total of 30 trials per phase).
Stanford University
Stanford, California, United States
Change in Recognition Memory (d-prime)
d' is a signal-detection sensitivity index-how well participants discriminate old (studied) from new (unstudied) items, independent of response bias. Computed as d' = Z(hit rate) - Z(false-alarm rate) from the old/new recognition memory test. Primary analysis is within-person Δhigh-confidence d' (based on "sure old" responses in the 4-point "sure old", "unsure old", "unsure new", "sure new" scale, Δ = active - sham) and Δoverall d' (based on "sure old" and "unsure old" responses). Main comparison is older vs. young, and within the older group also testing moderation by gut-brain axis measures and interactions with preclinical Alzheimer's disease pathology (pTau217, pTau181, Aβ42:40).
Time frame: post-active vs post-sham stimulation; up to 2 hours of task
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