Biology 202
2003 Second Web Paper
On Serendip

If brain equals behavior, then a relationship should exist between structural differences in the brain of abused children and changes in the behavior of abused children. Child abuse has been understood to have psychological effects, which are manifested by specific behaviors. Abused children express an array of behaviors ranging from depression, anxiety, post-traumatic stress and suicidal ideations to aggression, impulsivity, delinquency, hyperactivity and substance abuse (1). Furthermore, ten to twenty percent of adult survivors of child abuse suffer from dissociative or post-traumatic stress disorder (2). While there is a normal developmental path for the brain, childhood trauma can disrupt the progress and direction along this path. In response to physical and psychological trauma, a child's brain structure will change in ways that do not occur in children not exposed to trauma. These changes in the brain structure cause changes in behavior, including better or worse strategies for coping with the trauma of abuse. Therefore, changes in the brain and behavior due to child abuse suggest that environmental stressors can profoundly influence the development of the brain, and that the structure of the brain in turn controls behavior. Thus, just as the self acts on the environment, the environment acts on the self. Accordingly, understanding the effect of child abuse on the nervous system may help develop a clearer understanding of a model of the nervous system that incorporates the "I-function". This model in turn raises questions on the permanency of any definition of the "self".

An explanation for changes in the brain due to child abuse may involve the production or survival of neurons. A genetically predetermined, stepwise sequence develops the lower brain initially and then the higher brain centers develop gradually during childhood (3). Due to the sequential development of the brain, each stage depends on the healthy development of proceeding stages. In addition, there is a genetically determined sequential growth, proliferation and overproduction of axons, dendrites, and synapses in different regions of the brain (3). In any brain however, not all synaptic connections survive. Between the ages of three and eight, a child's brain has been shown to have twice as many neurons and connections than those of an adult brain (4). There are two environmentally dependent maturation processes of the brain with distinct critical periods. These critical periods are the times when the organizing systems of different functions are extremely sensitive to environmental inputs (5). Synaptic connections are eliminated if a particular experience does not occur during a critical period and new synapses are not generated or promoted if an experience does not take place. For an abused child, instead of a period of comfort and security, there are often periods of stress and fear (3). Furthermore, exposure to stress hormones released as a result of abuse significantly change the shape of the largest neurons in the hippocampus, kill neurons, or suppress the production of new neurons (6). For example, glucocorticoids are released during stressful periods and circulate for months, killing neurons and reducing the volume of the hippocampus (2). Thus, just as natural experiences can affect the survival or degeneration of neurons, the survival of neurons may possibly be the cause of structural variations within the brain of children who experience abuse.

Research comparing the brains of abused children and control subjects, primarily conducted by Martin Teicher, an associate professor of psychiatry at Harvard Medical School, has shown that abuse seems to induce a cascade of molecular and neurobiological effects that alter the development of specific areas in the brain. These areas include the limbic system, left hemisphere, corpus callosum and cerebellar vermis (6). EEG abnormalities in the left hemisphere were observed in sixty percent of 115 youngsters with documented histories of abuse (7). Similar brain-wave abnormalities are often seen in people with a greatly increased risk for suicide and self-destructive behavior (6). The limbic system is the brain's emotional processing center and includes the amygdala and hippocampus. MRI scans also revealed an association between early maltreatment and the reduction in the size of the adult left hippocampus or amygdala (6). Bermner et al. compared MRI scans of seventeen adult survivors of abuse with seventeen control subjects and found that the left hippocampus of abused subjects was twelve percent smaller (7). Teicher also observed a reduction in the left side of the brain that suggests that the right hemisphere was more active in the abused patients. Other research has found that these left hemisphere deficits may in turn contribute to the development of depression and increase the risk of memory impairments (8).

Animal and human studies have also shown that abuse can reduce the size of the corpus callosum by up to forty percent (9). The corpus callosum is the bundle of nerves that facilitates the communication between the right and left side of the brain. Teicher found that neglect was associated with a twenty-four to forty-two percent reduction in the size of various regions of the corpus callosum in boys while sexual abuse had no affect. The opposite was true for girls, who showed eighteen to thirty percent reduction due to sexual abuse, while neglect had no effect (8). The reduced of integration between the right and left hemispheres may predispose the patients to shift abruptly from the logical, rational, language controlling left side to the creative and emotional right side and remain in one hemisphere as opposed to moving seamlessly between the two sides (9). Many survivors of childhood abuse tend to reside in their left hemisphere when they function well but when traumatic thoughts arise, they retreat into the right hemisphere (9). In effect, abuse has rewired the nervous system to survive the traumatic experiences. Two primary adaptive response patterns to child abuse are the hyperarousal "fight or flight" response or the dissociative "freeze and surrender" response (10). Young children are most likely to use the dissociative response, which attempts to prevent memories from being integrated into the consciousness (10). The ability to limit the integration of memories may be the result of separating the functioning of the two hemispheres. Furthermore, the relatively unilateral use and development of one side of the brain could account for dramatic shifts in mood or personality (8).

Additionally, the cerebellar vermis is more active in abused children with a greater blood flow in the area (8). The cerebellar vermis is involved in emotion, attention and the regulation of the limbic system and is very sensitive to elevated stress hormones, particularly glucocorticoids (8). The greater degree of blood flow in the region may be aimed at controlling the electrical activity within the limbic system (8). While the cerebellar vermis attempts to maintain an emotional balance, trauma may impair its ability and as a result an individual may be particularly irritable (8).

Child abuse's effects on the brain often have a direct connection to the survivors' behavior and interaction with their environment. Abused children who alter their sense of consciousness are effectively altering their sense of self. A sense of self arises from one's own sense of identity combined with an interpretation of others reaction to the person's behavior. For victims of abuse, those behaviors may include imaginary companions or reach the point of a multiple personality disorder. The internal inputs to the nervous system that are struggling to define oneself through specific actions may conflict with the external inputs that are forcing an opposing reaction. This conflict can cause a person's consciousness to fragment, as the person must act out different messages from the subconscious. The I-function is involved in coordinating subconscious thoughts into behavior and ultimately produces a reaction, which may not be explained by a conscious thought. When the I-function receives signals, the response is to transmit the signals to the appropriate centers to organize appropriate behavior. The I- function tries to provide a coherent story with a seemingly logical response, while the story is split into two realities. One reality may be an internal and inherent fight or flight response, while the other reality is the external abuse, which forces a freeze and surrender response. While the system may expect inputs such as comfort and security, the reality of stress and rejection may cause a conflict that requires the nervous system to either become 'sick' or adapt its operating structure.

Although there may be a genetic template for the nervous system, environmental influences organize the nervous system and create individual connections that manifest in behavior. Examining neurons provides one method for noting physical changes in the brain due to abuse. Additional observations of connections between child abuse and biological changes in the brain support the contention that the brain is influenced by environmental factors and result in distinct behaviors. Abusive experiences may literally provide the organizing framework in the brain of a child. The organization of the brain includes the role of the I-function in formulating behavior and ultimately defining self. Instead of a box, the I-function should be represented as a dotted line surrounding an area that cannot be permanently defined because it is constantly changing as it adapts to varying realities. "Who am I?" is a question that can never be definitively answered. However, formulating a definition of "self" and "I" is significantly influenced by interactions throughout childhood. Therefore, it should be remembered that every individual has the power and choice to strengthen, as oppose to fragment, the mind of a child.

References

1)Relationship between Early Abuse, Posttraumatic Stress Disorder, and Activity Levels in Prepubertal Children

2) Hidden Scars: Sexual and other abuse may alter a brain region

3) Environmental Influences on Brain Development

4) Violent Changes in the Brain

5)
Development of the Cerebral Cortex: XIII. Stress and Brain Development: II

6)Psychological Trauma and the Brain

7)Psychological Abuse May Cause Changes in the Brain

8)McLean Researchers Document Brain Damage Linked to Child Abuse and Neglect

9)"Abuse stunts one part of the young mind, says a new study"

10)Childhood Trauma, the Neurobiology of Adaptation and Use-dependent Development of the Brain: How states become Traits"


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