An article in the March 2002 issue of Scientific American, entitled Scars That Won't Heal: the Neurobiology of Child Abuse, described presumably permanent damage to the developing brain as a result of severe neglect or repeated physical or sexual abuse. The changes were observed in studies of EEG's, which measure electrical activity in the brain, and MRI scans, which provide detailed pictures of the structure of the brain.
Specific findings were of several types. EEG studies showed a significant increase in the incidence of brain wave abnormalities in adult victims of incest or physical abuse compared with adults who had no history of abuse. Another study was cited in which adult victims of incest were found to have an increased incidence of seizure activity by EEG criteria.
MRI findings showed significant changes in the size of certain brain structures in people who had histories of abuse. The most striking finding was a decrease in the size of the left hippocampus, a structure responsible for storing new memories and which is connected to the limbic system, which regulates emotions. Another finding was a decrease in the size of the middle part of the corpus callosum, which contains the circuits that enable the two sides of the brain to communicate.
Functional imaging techniques looked at which parts of the brain "lit up" when subjects thought about disturbing memories and when they thought about emotionally neutral memories. In people with abuse histories, the right side of the brain appeared most active when processing emotional memories, while the left side was most involved in recalling neutral memories. People without such histories appeared to recruit both sides of the brain simultaneously in processing both emotional memories and neutral memories.
Do these studies demonstrate that childhood abuse and neglect cause permanent, unique, and irreparable harm to the developing brain? Perhaps, but they must be viewed in the light of studies of other conditions and in the light of what we know about the plasticity (changeability) of the structures in question.
Studies of adult patients with clinical depression have found that the left hippocampus of depressed people is significantly smaller than normal. One study found a 19% decrease in the size of the left hippocampus in depression, greater in magnitude than the decrease found in abused adults. In depression, at least, there is evidence that this "shrinkage" is reversible with certain antidepressant medications. It is not yet clear whether or not it is also reversible when recovery from depression occurs via psychotherapy alone.
How could damage to an organ that cannot repair itself be reversible? First, it is too simplistic to assume that a change in the size of a structure on an X-ray necessarily means that the structure has been damaged. Tissue studies in some depressed patients with decreased hippocampal volume failed to show significant numbers of dying cells. It remains possible that the changes in volume resulted from reversible changes in the shape of cells or in their geometric arrangement. Second, while much of the brain is incapable of generating new neurons beyond birth, the hippocampus is an exception, still capable of growing new functional nerve cells perhaps well into adult life. This structure can indeed repair itself.
Decreased size of the hippocampus is therefore not a unique finding in people with histories of abuse. It may, in fact, be a relatively common finding in many stress-related conditions. There is evidence that the hormones that the body produces in response to stress tend to reduce the size of the hippocampus. We may discover in time that this structure varies in size throughout life, shrinking in response to stress and recovering in size once stressful conditions have been relieved.
The altered relationship between the functions of the left and right hemisphere is most interesting. Normally, there appears to be a balance maintained between the functions of the two sides of the brain. We learned long ago by observing the effects of strokes, which damage specific parts of the brain, that the right hemisphere is associated with intense, often negative emotions, and that the left hemisphere tends to modulate these emotions.
If the frontal lobe of the left hemisphere is damaged by a stroke, patients often become deeply depressed, reacting as though an overwhelming catastrophe has befallen them. If the damage is in the right hemisphere, patients are often indifferent to their plight, which may be physically just as serious as that of the left hemisphere stroke victims. In fact, some may even fail to recognize that their bodies are malfunctioning.
If abuse victims have somehow learned to respond to some situations with their left brain and others with their right brain, one consequence might be alternating between periods of intensely painful emotions and periods of relative emotional numbness, much as we see in BPD. So the model fits, but is the malfunction permanent or reversible?
If this altered organization of brain function could be repaired, the endpoint would be a restoration of the normal balance between the hemispheres so that both sides respond together to any mental task. Eye Movement Desensitization and Reprocessing (EMDR), a treatment developed for the treatment of trauma, combines mental imagery with side-to-side rhythmic eye movements. One possible explanation of the power of this technique is that the side-to-side eye movements cause the left and right hemispheres to be alternately activated, bringing both sides of the brain to bear in processing memories that may have been stuck primary in one (presumably the right) hemisphere. EMDR may therefore be a means of reintegrating the functions of the hemispheres particularly in relation to previously traumatic memories. Perhaps functional brain imaging studies will eventually support this theory.
In summary, the findings of structural and EEG abnormalities in victims of abuse are probably valid and will likely be reproduced. These findings, however, may not be unique to this population, but may turn up in a variety of stress-associated conditions. The abnormalities, while impressive, may be reversible with both pharmacological and psychotherapeutic interventions. The brain is more plastic than we once believed. And we know that treatment can bring recovery both from BPD and from Post-Traumatic Stress Disorder.
© Dr. Richard Moskovitz
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as of March 21, 2002