Methods and systems are provided for delivering visible or infrared biostimulatory energy to bone marrow to subjects having or developing Alzheimer's disease. The radiation is delivered to sites remote from the brain at a dose sufficient to cause stimulated mesenchymal stem cells to appear in the brain and degrade β-amyloid. The energy may be coherent light and can be administered transcutaneously, subcutaneously, or via an intramedullary probe.