The goal of this clinical trial is to learn if personalized, multimodal imaging-guided, EEG-based closed-loop Temporal Interference Brain Stimulation (TIBS) can improve memory function in individuals with preclinical Alzheimer's Disease (AD).
The main questions it aims to answer are:
1. Does personalized TIBS lead to significant changes in functional connectivity strength of hippocampal-cortical networks at the end of the 2-week intervention compared to baseline? 2. What are the short-term (end of 2-week intervention) and medium-to-long-term (4 weeks and 12 weeks post-intervention) effects of personalized TIBS on episodic and working memory, as well as other cognitive domains in preclinical AD? 3. How does personalized TIBS modulate brain activity and connectivity, as measured by EEG power spectra and functional MRI (fMRI) functional connectivity, in preclinical AD? 4. What is the safety profile of personalized TIBS in this population?
Researchers will compare participants receiving active personalized TIBS to participants receiving sham (inactive) stimulation to see if TIBS effectively improves memory function and induces neural plasticity.
Participants will:
1. Undergo initial screening including neuropsychological assessments and blood p-tau217 testing to identify preclinical AD. 2. Receive either active personalized TIBS or sham stimulation daily for 40 minutes, 6 days a week, for 2 weeks. 3. Have individualized TIBS parameters (e.g., target localization, intensity) determined using baseline structural MRI and DTI. 4. Undergo real-time high-density EEG monitoring during daily stimulation sessions to enable closed-loop adjustment of stimulation parameters. 5. Participate in follow-up assessments at the end of the 2-week intervention, and at 4 weeks and 12 weeks post-intervention. 6. Receive multimodal imaging (sMRI, rs-fMRI, task-fMRI, DTI) and blood biomarker assessments at various time points. 7. Receive Aβ-PET and tau-PET scans, along with comprehensive neuropsychological assessments, at the 12-week follow-up. 8. Have their safety continuously monitored throughout the study.
Individuals recruited from neurology memory clinics or communities.
Age between 60 and 80 years old, inclusive; no gender limitation.
Right-handed.
Cognitive function test results within normal range after age, gender, and education-level adjustment, OR mild cognitive impairment not yet meeting diagnostic criteria for Mild Cognitive Impairment (MCI), OR only subjective cognitive decline.
Past or present neurological diseases (e.g., stroke, epilepsy, Parkinson's disease, multiple sclerosis).
Psychiatric disorders such as severe depression or severe anxiety.
Systemic diseases causing cognitive decline (e.g., severe thyroid dysfunction, severe liver or kidney disease, severe nutritional deficiencies).
Currently taking medications that may affect cognitive function (e.g., anticholinergics, benzodiazepines, antipsychotics) that cannot be discontinued or adjusted.
Parallel
Active TIBS
DeviceParticipants receive active TIBS targeted at the bilateral hippocampus. Stimulation parameters include a 5 Hz (Theta band) low-frequency modulation envelope, generated by two high-frequency current pairs (e.g., f1=2000 Hz, f2=2005 Hz). Peak-to-peak current intensity for each pair will be 2 mA (or 1 mA per electrode). Stimulation is delivered daily for 40 minutes, 6 days/week, for a total of 2 weeks. Individualized targeting and initial intensity optimization are guided by baseline sMRI and DTI. Real-time high-density EEG monitoring during each daily session (D2-D11) provides feedback on brain activity
Sham TIBS
DeviceParticipants receive sham stimulation designed to mimic the sensation of active TIBS without therapeutic output. This involves using a sham coil or a device mode with extremely low current intensity (e.g., 0.1-0.2 mA) or brief ramp-up/ramp-down sensations at the beginning and end of sessions, with no effective current delivery during the main stimulation period. The stimulation position and apparent parameters are identical to the active TIBS group to maintain blinding.
Change from Baseline in Functional Connectivity Strength of Hippocampal-Cortical Networks
Quantified by resting-state fMRI (rs-fMRI) functional connectivity strength within and between key memory-related networks (e.g., default mode network, hippocampal-cortical network) at the end of the 2-week intervention. Specific metrics will include ALFF, ReHo, FCS, and ACF.
Changes from Baseline in Hippocampal Gray Matter Density (sMRI)
Evaluation of changes in hippocampal gray matter density or volume, quantified using structural Magnetic Resonance Imaging (sMRI). This measure assesses the structural integrity and potential atrophy or increase in gray matter in a key brain region associated with memory.
Changes from Baseline in Cortical Thickness (sMRI)
Evaluation of changes in cortical thickness across various brain regions, quantified using structural Magnetic Resonance Imaging (sMRI). This measure assesses the integrity and potential thinning or thickening of the cerebral cortex.
Changes from Baseline in Resting-State Functional Connectivity (fMRI)
Evaluation of changes in resting-state functional connectivity using functional Magnetic Resonance Imaging (fMRI). This assesses the temporal correlations between spontaneous fluctuations in BOLD signals across different brain regions, reflecting synchronized neural activity. Specific brain networks (e.g., Default Mode Network, Salience Network) or seed-based connectivity will be analyzed.
Changes from Baseline in White Matter Integrity (DTI)
Evaluation of changes in white matter integrity, assessed using Diffusion Tensor Imaging (DTI). Key metrics to be analyzed include Fractional Anisotropy (FA), Mean Diffusivity (MD), Axial Diffusivity (AD), and Radial Diffusivity (RD), reflecting the directionality and magnitude of water diffusion in white matter tracts.
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