Vol 6 n° 2 - Neuroplasticity
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hose  of  us  who  study  the  nervous  system believe  that  the  brain  is  the  organ  that  controls  our behavior. Therefore, what we think and what we do, while obviously influenced by the experience, are results of the brain’s processing of information and directing our subsequent actions. Given this basic assumption, it is no wonder that the most common model or analogy of how the brain operates is that of a computer. While this analogy may have some heuristic value, it is likely wrong or at least very limiting.The brain is an organ, like the liver, heart, and kidney, and is made of chemicals, cells, and tissue. Communication between brain cells is mediated through neurons with long processes (axons) that connect many cells at once and release small batches of chemical infor- mation (neurotransmitters) to a network of other neu- rons. The neurons receive the signals on their antennae, called dendrites, which protrude, in many cases, quite elaborately from the cell body. The specific site where the chemical signal from one cell makes contact with another cell is called a synapse, which is made up of sig- naling cells (presynaptic boutons) and receiving cells (postsynaptic spines). The synapse is the structural unit that transmits the majority of information between neu- rons. Each neuron can have thousands of these synapses on its dendrites and cell body.The real trick for the neu- ron is to calculate (interpret) the temporal and spatially transmitted  information  it  receives  and  to  send  that interpreted message onto the next neurons in a circuit. The aggregation of this information passing and pro- cessing results in thought and behavior. Adult neural stability One of the main reasons for viewing the brain as a sta- ble machine or computer is because this analogy helps explain how we can remember from one instant to the next. If the underlying structure was changing all the 1 3 5 B a s i c   r e s e a r c h T Copyright © 2004 LLS SAS.  All rights reserved www.dialogues-cns.org Structural plasticity of the adult brain Fred H. Gage, PhD The adult brain has long been considered stable and unchanging,  except  for  the  inevitable  decline  that occurs with aging. This view is now being challenged with clear evidence that structural changes occur in the brain throughout life, including the generation of new neurons and other brain cells, and connections between and among neurons. What is as remarkable is that the changes that occur in the adult brain are influenced by the behaviors an individual engages in, as well as the environment in which an individual lives, works, and plays. Learning how behavior and environment regulate brain structure and function will lead to strategies to live more effective lives and perhaps protect from, or repair, brain damage and brain disease. © 2004, LLS SAS Dialogues Clin Neurosci. 2004;6:135-141. Keywords: neurogenesis; adult stem cell; brain structure; neurological disease; depression Author affiliations: Laboratory of Genetics, The Salk Institute, La Jolla, Calif, USA Address for correspondence: Fred H. Gage, PhD, Laboratory of Genetics, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
(e-mail: gage@salk.edu)