Current research suggests that levels of brain-derived neurotrophic factor (BDNF) and certain excitatory neurotransmitters - specifically glutamate, D-serine, and glycine are low in participants with depression and other mental illnesses (Wolkowitz and Reus 2002, Tan et al., 2005; Shoval & Weizman, 2005; Hashimoto et al., 2005). Research also suggests that levels of both BDNF and excitatory transmitters can be enhanced by cognitive stimulation (Hynd et al., 2005; Wu et al., 2005; Yang et al., 2005; Mattson et al., 2004). BDNF is found in brain tissue and is also measurable in blood; it stimulates neuronal cell growth in certain brain regions (Duman, 2004). In Phase 1, we wish to measure the levels of specific neurotrophic factors in healthy, young participants. Phase 2 is intended to correlate similar levels with change in neurocognitive performance in healthy, older participants. Overall, this study is designed to obtain a raw measure of the impact that cognitive training has on the mature adult brain.