Background: A significant potential exists to modify the structure and function of the aging human brain given intensive mental stimulation and physical activity. Age-related cognitive decline has consistently been identified on frontal lobe measures of executive control such as reasoning. Concomitantly, a greater vulnerability of frontal brain networks, which subserve executive control functions, has also been identified with aging. Preliminary evidence highlights the potential of reasoning training as well as physical training to modify and strengthen brain and cognitive function in seniors. Evidence from our lab indicates that frontally mediated, gist-based reasoning (defined as the ability to combine detail information to construct abstract meanings) offers a promising cognitive domain to train. Extracting gist meaning from the massive amount of incoming information is one of the most vital mental skills a healthy mind achieves. Purpose: This proposal is an innovative study to obtain data regarding the benefits of a (a) novel gist-based reasoning training program or (b) physical training on frontal-lobe mediated cognitive measures of executive control in cognitively normal seniors. The project will also employ newly developed (a) brain measures to chart changes in brain blood flow and connectivity combined with (b) a cognitive activation task specifically designed to measure brain regions engaged in gist reasoning versus detail processing. The project also examines shorter dose effects, i.e. after 6 weeks and 12 weeks, than previously examined as well as individual differences based on high and low performers for gist and physical training. Methods: 60 cognitively normal seniors between the ages of 60 and 75 years will be recruited for study and randomized into 1 of 3 groups. Each group will consist of 20 participants each: a reasoning-trained, a physical-trained and a wait-listed control group. Participants will be comprehensively screened to insure they are cognitively normal. Prior to intervention, participants' baseline gist and detail processing ability, battery of cognitive functions and fitness measures will be obtained. Structural and functional brain measures will also be obtained. Participants will undergo 12 weeks of gist-based training or physical training with measurement at midpoint, 6 weeks of training, endpoint 12 weeks of training and 4 weeks after training is completed. Training effects will be measured behaviorally in trained areas (reasoning \& physical) and untrained cognitive areas. Additionally, structural and functional brain imaging will measure changes in cerebral blood flow, global and regional brain volume, white matter tracts, efficiency, activation patterns, and blood oxygenation with a particular focus on changes to frontal regions. Significance: The current study seeks to discover neuroprotective, nonpharmacological interventions that could prevent mental decline and strengthen cognitive brain health in seniors, with possible societal savings of billions of dollars. This will be one of the first training studies to explore short-term intensive reasoning and physical training, each documented as pivotal to cognitive brain health with the potential to strengthen frontal regions against the losses associated with aging.