The opening chapter of Horizons in Neuroscience Research. Volume 37 suggests a definition and temporal origin of languages that emerge naturally-without linguistic assumptions or preconceptions-from an analytic and predictive theory of mental evolution. A significant number of Alzheimer's disease patients present with low circulating plasma leptin levels. As such, studies expressed in the following chapter have shown that leptin treatment reduces amyloid and phosphorylated tau accumulation in cultured cells and animal models, with beneficial effects. A systematic review of the structure and function of the cerebellum in normal brain and surveys the distribution of the pathology in a major molecular group of neurodegenerative disease is presented, inclduing Alzheimer's disease, argyrophilic grain disease, corticobasal degeneration, chronic traumatic encephalopathy, guam parkinsonian dementia complex, primary age-related tauopathy, and progressive supranuclear palsy. The application of Fourier analysis is illustrated with reference to the spatial distribution of intracellular neurofibrillary tangles in the cerebral cortex and hippocampus of six cases of Alzheimer's disease, and it is suggested as a useful statistical method for studying the patterns of intracellular neurofibrillary tangles. Additionally, the structure and function of the basal ganglia in normal brain are described, and the role that differential pathology in these regions may have in determining the clinical symptoms in neurodegenerative disease is explored. The authors describe the structure and function of the superior colliculus in the normal brain, as well as the pathological changes in the superior colliculus which may explain eye movement problems in two neurodegenerative disorders: progressive supranuclear palsy and chronic traumatic encephalopathy. The results obtained in the penultimate chapter corroborate the toxic effects at cellular and molecular levels that the administration of L-DOPA has, even in a healthy system, affirming the need to find a Parkinson disease treatment alternative. The final study investigates the relationship between the number of flow experiences in daily life and brain activation by near-infrared spectroscopy.