The purpose of this study is to see if stimulation of the brain can improve memory. The investigators will use a device called transcranial magnetic stimulation that can stimulate and activate a specific part of the brain that is important for memory. The study will enroll subjects with MCI (mild cognitive impairment) who will be randomly assigned to receive active or sham brain stimulation. ‘Blinded’ or ‘sham-controlled’ means that the subject will not know whether the treatment they receive is the active treatment or the non-active stimulation. In the ‘sham’ condition, the stimulator will turn on but will not actually be stimulating the target brain region.