2. Analogical reasoning requires that subjects adequately process different forms of information and then perform a mapping process that allows them to recognize the similarity between two or more forms of information. Evidence has been provided that indicates this process of analogical mapping is subserved by the frontal cortex. We plan to study a group of normal volunteers, and three groups of patients who demonstrate impaired performance on tests of analogical reasoning and problem-solving: those with Parkinson's disease, frontal lobe dementia, and focal frontal lesions. We predict that subthreshold rTMS will facilitate analogical reasoning by promoting the activation of established or novel neural activation patterns that represents the actual mapping and decision processes required for analogical reasoning. Additionally, we expect to facilitate response times and accuracy in analogical mapping in those patients that exhibit abnormal analogical reasoning performance.