Brain Plasticity and Recovery of Function in Adulthood
When the brain is damaged, many neurons that are not directly injured lose their normal synaptic inputs. This synaptic loss leads to three possible fates in the deafferented neurons: (a) death; (b) survival with reduced total input; and (c) reinnervation, either in whole or in part. In most cases all three events occur after injury. Although reinnervation was once thought to be a rare event, a view has emerged in the last decade that the replacement of damaged connections following neural injury is actually the rule in the central nervous system. What is less clear, however, is whether reinnervation is functionally advantageous or whether it might actually interfere with normal functioning.
Behavior also changes when the brain changes. When behavior changes, experience changes too. Consider an example in which a person has a stroke that renders her unable to move one arm. The likely effect of this functional loss will be the increased reliance on the other limb, which means the brain controlling that limb will be more active. We saw in Chapter 2 that when animals are trained to use a specific limb, there are changes in the neurons controlling the limb. It is therefore reasonable to expect that the brain will change after our hypothetical stroke because the behavior has changed. Thus, a brain injury can change the behavior, which in turn changes the brain. These behaviorally induced changes need not be in the vicinity of the injury and very often are not even on the same side of the brain as the injury. The possibility that behavior can change the brain after injury is not normally appreciated in studies of plasticity, but it is fundamental to understanding the brain -- behavior correlations during recovery. It is also crucial to the issue of establishing behavioral therapies to assist restitution of function. I return to this issue later.
In this chapter I focus on the changes in the brain in response to cortical
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Publication information: Book title: Brain Plasticity and Behavior. Contributors: Bryan Kolb - Author. Publisher: Lawrence Erlbaum Associates. Place of publication: Mahwah, NJ. Publication year: 1995. Page number: 95.
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