Neurostimulation In Adult Survivors of Childhood Acute Lymphoblastic Leukemia (ALL)

Digit Span Backward: Digit Span Backward (DSB), from the Digit Span subtest on the WAIS-IV, is a measure of working memory. The number of digits recalled in the longest span is converted to a standard z-score using age-based norms (Mean=0, SD=1).

Trail Making Test Part B (Trails B): This is a timed task that requires a participant to shift his/her attention adaptively and flexibly. Age-based standardized z-scores are calculated (Mean=0, SD=1).

Controlled Oral Word Association (COWA): This is a task of cognitive/verbal fluency that measures spontaneous production of words beginning with a designated letter or category. Age-based standardized z-scores are calculated (Mean=0, SD=1).

Patient reported symptoms of executive dysfunction will be evaluated via the Childhood Cancer Survivor Study Neurocognitive Questionnaire (CCSS-NCQ). The CCSS-NCQ is a 32-item questionnaire evaluating 4 domains of executive function. Z-scores (M=0, SD=1) are calculated using sibling data from the Childhood Cancer Survivor Study.

Patient reported symptoms of executive dysfunction will be evaluated via the Behavior Rating Inventory for Executive Function - Adult Version (BRIEF-A). The BRIEF-A is a 75-item measure of executive function that provides age- and sex-specific national normative data for nine domains of executive function (T-Score, M=50, SD=10).

White connectivity will be measured via diffusion tensor imaging and resting state fMRI (rsFMRI). The cortex will be parcellated into anatomical regions based on the high-resolution T1-weighted imaging using the FreeSurfer software (http://surfer.nmr.mgh.harvard.edu/). Probabilistic fiber tracking will be performed for individual seed points within the gray matter/white matter surface for each parcellated cortical region to evaluate strength of the connectivity between each individual region and every other region. The current project will focus analyses on the frontostriatal connections from the DLPFC to the striatum. rsfMRI data will be used to construct functional connectomes for each participant at each time point. We will measure several common connectome properties including global and local efficiency. Connectome modularity, degree distribution, and hub characteristics will also be measured.

Regional brain activation will be assessed using an N-Back Task. This task requires a participant to respond to a presented stimulus only when it is the same as one presented on a trial at a predetermined number prior to the current trial. For this study, we plan to use 1-back and 2-back trials. Improved efficiency will be defined as reduced activation in dorsolateral prefrontal cortex during performance on the N-Back task during the fMRI. Using Statistical Parametric Mapping software (SPM12, Wellcome Trust Centre for Neuroimaging, London), contrast-images from the fixed-effect analysis in each subject will be used for second level random-effect analysis to create group activation maps. These contrasts include pre- v. post-intervention imaging during the N-back task. Participants assigned to active stimulation will then be contrasted to those assigned to sham stimulation.