Neuromodulation of Memory in Aging

Working Memory Task

The difference in memory accuracy between TMS conditions (random vs. ordered vs. sham stimulation) on a working memory task. Each trial of the task consists of stimulus presentation of an array of letters, a delay period in which subjects alphabetize the letters, and probe period where subjects indicate whether the number corresponds to the alphabetized position of the letter probe presented. Memory is subsequently assessed as a function of TMS condition.

Functional network connectivity

Functional network connectivity/activity is estimated by comparing the hemodynamic time courses of two or more regions of the brain. The correlation between the time courses of each pair of regions is termed functional network connectivity. The Working Memory Network (WMN) is identified by comparing fMRI-based functional network connectivity for high vs low working memory load (e.g., remembering 4 versus 3 items).

Vascular density (VAD)

This measure of neurovascular brain health, vascular density (VAD), as estimated by an automated method of segmenting veins with a magnetic resonance imaging (MRI) sequence known as susceptibility weighted imaging. This measure can be used to estimate the dilation of cerebral veins, and therefore VAD.

EEG-based connectivity

EEG data will be source reconstructed to a fine-grained grid and timecourses of the solution points are averaged per region and per subject. The imaginary part of the coherence (iCoh) of averaged EEG source signals will be assessed within the alpha and theta frequency bands to build EEG-based connectivity matrices ("connectomes") for alpha- and theta-based connectivity, for each subject.

Montreal Cognitive Assessment (MoCA)

The MoCA was designed as a rapid screening instrument for mild cognitive dysfunction. This widespread tool is used to assesses different cognitive domains: attention and concentration, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculations, and orientation. The principle outcome measure is a summary score combining performance on each subtest. Scores range from 0 to 30. A higher score indicates intact cognitive functions.

National Institutes of Health (NIH) Toolbox Cognitive Battery

The primary outcome measure of the NIH Toolbox is a Crystallized or Fluid Intelligence score. Fluid intelligence involves comprehension, reasoning and problem solving, while crystallized intelligence involves recalling stored knowledge and past experiences. These scores are normalized and scaled to reflect a 1-100 range. Higher scores indicate better performance.

Hopkins Verbal Learning Test (HVLT-2)

The Hopkins Verbal Learning Test (HVLT-R) consists of memorization of a list of words to test the ability to recall immediately after memorization (immediate recall) and after a 20-minute delay (delayed recall). These scores are normalized to reflect a 1-100 percentile range. Higher scores indicate better performance.

Brief Visuospatial Memory Test (BVMT-R)

The BVMT-R is a commonly used assessment tool to measure visuospatial learning and memory. A visual display of six simple figures arranged in a 2 × 3 matrix is shown to participants for three consecutive 10-second trials. Scoring of the immediate and delayed recall as well as copy trials are based on the accuracy of the drawings and the location of the figures. These scores are normalized to reflect a 1-100 percentile range. Higher scores indicate better performance.