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Q: Many people assume that brain growth, and especially the development of new neurons, ceases during childhood. Is there any truth supporting this assumption? A: When I went to graduate school, there was a belief that you did not form new neurons or new synapses after infancy. But researchers have discovered that new synapses form in adult rats. If an adult rat learns a new motor response (i.e., pushing its paw against a lever), you can actually trace the formation of a new synapse in the brain of that rat. The belief that new neurons could not grow in adults was first refuted by studies of songbirds that took place about 30 years ago. It was discovered that new neurons would grow when certain songbirds learned a new song. And now, there is clear evidence demonstrating that new neurons grow in adult monkeys, in cats, and in other mammals. This neuron growth takes place in at least two regions of the brain, namely the hippocampus and the olfactory cortex. The hippocampus is extremely important for memory functions, such as turning short-term memories into long-term memories. In adult monkeys, it seems that new neurons are growing and moving into the hippocampus on a regular basis. Comparable to the songbirds that need new neurons to learn new songs, monkeys—and, most likely, other primates—apparently need new neurons to develop at least some of their new memories.
Q: The loss of brain tissue is almost always associated with degenerative illness and/or brain damage. When does losing brain tissue actually help us during the learning processes? A: We now know that most loss of brain tissue in infants and children—and even in adults—is positive. It is the pruning away of the connections and neurons that aren’t very effective. In short, it is impractical to maintain millions of neurons that are not very useful, so these extra neurons die off. This discovery completely revolutionized the understanding of how the brain works. A major part of learning is the process of getting rid of what doesn’t work very well. Learning is not just figuring out how to do something; it is also the process of figuring out how not to do something. Q: How accurate is the conception that our brain functions are extremely localized? And how does this relate to the notion that an individual may be either left-brained or right-brained? A: There are many beliefs about brain localization that are quite inaccurate. For instance, language is not located entirely in the left hemisphere, and spatial skills are not found only in the right hemisphere. In reality, both functions are present in both hemispheres. At the same time, there is some localization of function, so you are more likely to have the sound analysis of particular musical pieces done primarily in the left hemisphere, while you are more likely to have the global analysis of the meaning of a sentence done primarily in the right hemisphere. But even these examples, that demonstrate a certain degree of localization, are not functions that reside entirely in one hemisphere. We work with a few kids who actually have only one hemisphere, and they are veritable left- or right- hemisphere people because of surgery that they’ve undergone for epilepsy. For most of us, however, understanding where specific brain functions take place is extremely complex, and they are not limited to one hemisphere or the other. Q: What do the realities of learning and the brain indicate for the recuperation of people who have been abused or had other traumatic experiences? A: There has been an enormous amount of work on traumatic experiences and learning in animals, including the study of particular neural changes that happen within the brain after a traumatic experience. This work has clearly demonstrated that specific circuits exist for remembering trauma, and that we seem to have a special way of remembering our traumatic experiences. We can vividly recall trauma after one experience, whereas we typically require several experiences to remember something that is not traumatic. I do some work with abused children. It is important to recognize that there are many different patterns of abuse, and the effects these patterns have on the children can vary enormously, depending on the kind of abuse. In order to help an abused individual, you must carefully consider his or her particular experience. Most of the time, studies of the brain are too coarse to provide immediately useful insight into a specific case. Finding distinct brain activation patterns in abused children, for example, is very interesting but does not necessarily help for the treatment of one child. It is, therefore, far more important, when working with abuse victims, to try to understand each person’s particular adaptation to the abuse. Once children have been severely abused, they will probably never get rid of the effects of the abuse. But they can learn to behave in specific adaptive ways that will allow them to function quite well most of the time, such that they can build stable and good lives. For More Information
HGSE News, Harvard Graduate School of Education
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