High Frequency Stimulation to Improve Cognition, Mobility, and Affect in Individuals With and Without Subjective Cognitive Decline

Cognition - The Tablet-based Cognitive Assessment Tool (TabCAT)

This test battery assesses performance in various cognitive components. A composite score across subtasks will be computed. Higher scores in the composite indicates better cognition.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Mobility - Grip Strength

This test assesses grip strength in kg. A composite score across trials will be computed. Higher scores indicate more strength.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Mobility - 10 Meter Gait Speed

This test assesses speed in seconds during unassisted walking for 10 meters. A composite score across trials will be computed. Higher scores indicate lower walking speed.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Mobility - Clinical Test of Sensory Interaction on Balance (CTSIB)

This test assesses sway area (measured in m\^2/s\^4) with eyes open and closed while standing on a hard and a foam surface. A larger sway area indicates greater postural instability and poorer balance control during specific sensory conditions

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Affect - Profile of Mood States Second Edition (POMS-2)

This questionnaire assesses transient feelings and mood on a scale from 0 = not at all to 4 = extremely). A composite score across items will be computed as primary outcome. Higher scores indicate greater intensity of the mood state.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Affect - Ryff Scales of Psychological Wellbeing

This questionnaire assesses psychological well-being via 42 statements using a 6-point scale (1 = strongly agree; 6 = strongly disagree). A composite score across items will be computed as primary outcome. Higher scores indicate greater psychological wellbeing.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Affect - Satisfaction with Life Scale

This questionnaire assesses satisfaction with life. A composite score across items will be computed as primary outcome. The possible range of scores is 5-35. Scores between 5-9 indicate the respondent is extremely dissatisfied with life, whereas scores between 31-35 indicate the respondent is extremely satisfied. A composite score across items will be computed as primary outcome. Higher scores indicate greater life satisfaction.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Brain Markers - Structure

Cortical thickness (in mm) will be determined via a T1 MRI scan in dorsolateral prefrontal, sensorimotor, and insular cortices using the CAT computational anatomy toolbox. Greater values indicate greater cortical thickness.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

AD Biomarkers - Amyloid

These assays will determine amyloid (e.g., Aβ17) sensitive to Alzheimer's Disease. Higher values indicate higher amyloid levels.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Biomarkers - P-Tau

These assays will determine p-tau levels sensitive to Alzheimer's Disease. A composite score across items will be computed as primary outcome. Higher values indicate higher p-tau levels.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)

Brain Markers - Network Function

Brain network function will be assessed via resting-state fMRI (in Blood oxygen level dependent response) to capture functional segregation of dorsolateral prefrontal, sensorimotor, and insular networks using the CONN toolbox. Greater values indicate greater functional connectivity.

Time frame: Baseline, halfway through (1.5 months), and post-intervention (3 months)