Neuroimaging studies have identified cognitive tasks that can selectively activate specific parts of the brains. However, the subsequent effect of localized brain activation on the cognitive functioning remains unclear. We discovered that after being engaged in the novel picture encoding task to activate hippocampus for 2 min, individuals demonstrated better memory, but not motor function. Similarly, after performing the finger sequencing task to activate the primary motor cortex, individuals showed improvement in motor function, but not in memory. These double dissociation results suggest that when we selectively activate specific part of the brain, the cognitive function mediated by that particular region but not the others can consequently be improved.