Targeted Transcranial Magnetic Stimulation to Improve Hippocampal-dependent Declarative Memory Abilities

The investigators propose a pilot study of the potential for non-invasive transcranial magnetic stimulation (TMS) to improve memory in healthy adults (young and old) and to treat memory deficits in older adults with amnestic mild cognitive impairment (aMCI). aMCI is a condition that frequently precedes Alzheimer's disease (AD), and a key symptom of aMCI is clinically significant memory loss (i.e., rapid forgetting) greater than expected for age. The investigators will test whether a form of non-invasive brain stimulation repetitive transcranial magnetic stimulation (rTMS) can improve memory abilities in healthy young adults, healthy older adults, and older adults with aMCI by retuning memory-related brain networks. This study's specific aims are to: 1) Measure changes in declarative memory performance after treatment with targeted rTMS; 2) Measure modulation of functional brain networks after treatment with targeted rTMS. To achieve these aims, the investigators will recruit participants from a standing registry and other sources, test their memory abilities, apply rTMS to a specific brain region, and then test their memory abilities again. As a control, all participants will receive sham rTMS that does not stimulate the brain in one of the two phases of participation. By testing whether real rTMS improves memory abilities more than sham rTMS, the investigators will determine whether rTMS can reliably improve memory in the populations of interest. Also, the investigators will measure changes in brain activity before and after stimulation using magnetic resonance imaging (MRI) and magnetoencephalography (MEG). This study is a key first step which will support the investigators' long-term goal of treating memory deficits in neurological patients. The investigators expect that rTMS will improve memory abilities in all participants, and that the improvements in memory will be attributable to changes in the connectivity of memory-related brain networks. This study has clear clinical and translational relevance because it adapts a novel technique addressing a key symptom of AD to new populations. The investigators expect that the findings will improve the field's understanding of memory loss in healthy aging, aMCI, and AD.

All procedures are identical in both arms with the exception of the order of stimulation administration. In Arm A, transcranial magnetic stimulation (TMS) will be applied in the first week of participation, and sham stimulation will be applied in the second week of participation.

Device: Transcranial magnetic stimulation

All procedures are identical in both arms with the exception of the order of stimulation administration. In Arm B, sham stimulation will be applied in the first week of participation, and transcranial magnetic stimulation (TMS) will be applied in the second week of participation.

Device: Transcranial magnetic stimulation

Transcranial magnetic stimulation non-invasively applies very small amounts of electrical current to brain tissue; sham stimulation uses the same approach but applies little or no actual stimulation to the brain by using less power or greater distance between the head and the stimulator.

Plazo: Potential changes will be assessed after each one-week rTMS treatment period. Results will be reported at the end of the study (approximately one year).

The investigators will measure memory performance before and after treatment to determine whether performance differs as a result of treatment. The main task will be a face-word association task in which participants will study a list of faces paired with single words. After a short delay, one studied face will be presented at a time, and participants will be prompted to recall the word associated with the face. The number of correct face-word associations recalled is the dependent measure.

Plazo: Potential changes will be assessed after each one-week rTMS treatment period. Results will be reported at the end of the study (approximately one year).

The investigators will use MRI and MEG to measure brain function before and after treatment to determine whether brain function differs as a result of treatment.

Targeted Transcranial Magnetic Stimulation to Improve Hippocampal-dependent Declarative Memory Abilities