Stimulation to Improve Memory (STIM)

Testing High Definition Transcranial Direct Current Stimulation (HD-tDCS) as Treatment of Mild Cognitive Impairment

This study will test the effects of different doses of a form of non-invasive brain stimulation for the treatment of individuals with mild cognitive impairment (MCI) and dementia of the Alzheimer's Type (DAT).

This research study is being done to learn important information about the effects of weak electrical stimulation on brain functioning in those with mild cognitive impairment (MCI) and dementia of the Alzheimer's type (DAT). The findings will help determine "how much" stimulation is needed to enhance memory and thinking abilities, how it affects brain functioning, and who is most likely to benefit. Ultimately, this information may guide treatment efforts for those at various stages of Alzheimer's disease. The study will use brain imaging to see whether these treatments change how participants learn and remember information. Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans will be used. The study will also use cognitive tests and questionnaires to examine whether participants' memory (and related abilities) change because of treatment. The study will enroll participants with a diagnosis of MCI or DAT. It is expected but not required that participants will be co-enrolled in the University of Michigan Memory and Aging Project (UM-MAP; HUM00000382).

Eligible participants will be randomized 1:1:1:1 to receive either sham, 1mA, 2mA, or 3mA HD-tDCS for at least 5 sessions and up to 30 sessions using a blocked randomization design.

Working memory accuracy measured by a discriminability ratio (2-back d' minus 0-back d') on a validated computerized N-Back task, measured after baseline (Session 1) and every intervention session (Sessions 2-6)

Verbal memory accuracy measured by an accuracy score (percent correct) on a computerized Paired Associates task, measured after baseline (Session 1) and every intervention session (Sessions 2-6)

Verbal memory reaction time measured by a drift rate score (V; measured by the mean rate at which information is accumulated towards a boundary [correct or error response]) on a computerized Paired Associates task, measured after baseline (Session 1) and every intervention session (Sessions 2-6)

Evaluated using standard questionnaires that arose from comprehensive reviews of the tDCS literature, this questionnaire was recently refined to include pre- and post-HD-tDCS symptom assessment. This will be administered prior to and immediately after every brain stimulation session (including sham).

Evaluated using a standard single question administered after every brain stimulation session (including sham).

Graph Theory Analysis via fMRI using arbitrary units of connectivity strength to measure changes in the Default Mode Network, along with strength in and between other networks

A priori intent to measure through change in the NIH Toolbox Flanker Inhibitory Control and Attention Test Score

A priori intent to measure through change in the NIH Toolbox Pattern Comparison Processing Speed Test Score

A priori intent to explore d' change for each N-Back task condition (2-back, 0-back) in order to understand the overall effect of the HD-tDCS on task performance.

Measured through change in Cogstate or other comparable computerized cognitive testing scores across consecutive daily sessions

Inclusion Criteria: Diagnosis of Mild Cognitive Impairment (MCI) or dementia of the Alzheimer's type (DAT) Must be MRI compatible, criteria that also apply for High Definition transcranial direct current stimulation (HD-tDCS; e.g., absence of metallic or electronic implants in the upper body or head) Stable on relevant medications for at least 4 weeks prior to study enrollment Exclusion Criteria: Certain neurological diseases Certain psychiatric conditions Severe sensory impairment