Diminishing Accelerated Long-term Forgetting in Mild Cognitive Impairment

This study is designed as a prospective, double-blind, placebo-controlled, randomized parallel-group study that will be completed at the clinical research facility at St. James\' Hospital and at Trinity College Dublin, Ireland. A total of 100 amnestic mild cognitive impairment (aMCI) patients will receive a (real or control) non-invasive transcutaneous electrical stimulation procedure. Patients will be assigned to one of four groups. One group will receive active stimulation, while the three groups will be control groups. One groups will be receive sham stimulation (inactive control), while a second group will receive active stimulation and local anesthesia and a third group will stimulate a different nerve (active control; same sensation different nerve). The investigators will include three control groups to verify that the effect is real and location specific and cannot be associated to a sensation effect. The investigators have opted to use a parallel-group design as it is unclear what the carry-over effect and/or wash-out period will be for stimulation. To eliminate subjective bias, all patients and the investigator testing the endpoint measures will be blinded to the type of intervention. The primary outcome, i.e. memory recall, will be determined by a word association task recorded immediately after stimulation, 7 days after stimulation, and 28 days after stimulation. The secondary outcomes is neurophysiological changes determined by resting state EEG, which will be assessed immediately before and after stimulation in the first session. The investigators will conduct this study as follows: 1. Screening aMCI patients. 2. Randomly assigning aMCI patients to one of the four groups. 3. Administering one session active stimulation (n = 25) or control (n = 25 in each of three control group) stimulation paired with a word-association task; administered by research assistant. 4. Behavioral assessments after each of the three blocks of studying the word associations and neural measures immediately after the last session of Behavioral assessments (T0). 5. Behavioral assessments at seven (T1) and 28 (T2) days after stimulation.