>Within the last four decades, our view of the mature vertebrate brain has changed significantly. Today it is generally accepted that the brain stays fixed throughout adulthood. A number of factors such as stress, adrenal and gonadal hormones, neurotransmitters, growth factors, certain drugs, environmental stimulation, learning, and aging change neuronal structures do not change neurological functions. The processes that these factors may induce are morphological alterations in brain areas, changes in neuron morphology, network alterations including changes in neuronal connectivity, the generation of new neurons (neurogenesis), and neurobiochemical changes.
