This study will probe if the biological changes in amnestic mild cognitive impairment (aMCI) are related to a history of mild traumatic brain injury (mTBI) using high definition transcranial direct current stimulation (HD-tDCS) and blood-derived biomarker tools. Participants who Do as well as those who Do Not have a history of mTBI will be enrolled in the study.
Active diagnosis of amnestic mild cognitive impairment
Presence of an mTBI history for the mTBI+ group; absence of an mTBI history for a control sample
Female and male subjects
All races/ethnicities
Mild traumatic brain injury within past year
Lifetime history of moderate or severe brain injury
Lifetime major neurologic syndromes (e.g., stroke, epilepsy, brain tumor)
Lifetime major cardiovascular conditions (e.g., heart attack, heart failure)
Crossover
High Definition Transcranial Direct Current Stimulation
DeviceHD-tDCS for this study is not intended to be a treatment, and will be applied continuously for 30 minutes at sham (0 mA) or 2 mA for active conditions across 3 consecutive daily sessions to probe neural circuit integrity. This specific HD-tDCS device is completely computer driven, running on a laptop using specialized software. Circular electrodes (12-mm in diameter) filled with conductive gel will be placed in a 4x1 ring configuration with the central electrode being the anode surrounded by four cathodes.
Changes in Rey Auditory Verbal Learning Test Score
The RAVLT is a verbal episodic memory test that is sensitive to mesial and lateral verbal episodic memory circuit dysfunction. The primary outcome measure for this task is the total number of items immediately recalled during the learning trials and after the 20 minute delayed recall trial. Changes in scores from baseline to testing immediately following the completion of each condition will be examined.
Changes in Delis Kaplan Executive Function System (DKEFS) Trail Making Test
The DKEFS Trail Making Test is a measure of cognitive flexibility and executive functions. The task requires the subject to as quickly as possible complete five conditions, involving number cancellation, number sequencing, letter sequencing, number-letter switching, and line tracing. The outcome measure for this task is the time to complete each of the five conditions. Changes in scores from baseline to testing immediately following the completion of each condition will be examined.
Changes in Delis Kaplan Executive Function System (DKEFS) Color-Word Interference Test
The DKEFS Color-Word Interference test is a measure of information processing speed and complex attention. The task requires the subject to as quickly as possible complete four conditions, involving color naming, word reading, response inhibition, and then switching back-and-forth between two response patterns. The outcome measure for this task is the time to complete each of the four conditions. Changes in scores from baseline to testing immediately following the completion of each condition will be examined.
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