This is my summary of information contained in Teicher, Martin H.  Wounds that time won’t heal: The Neurobiology of Child Abuse.  Cerebrum 2(4):50-67, Fall 2000 issue.  There is much more information in the paper itself.

There is a constellation of abnormalities associated with child abuse that is separate from any direct damage to the head.  Dr. Teicher says, “Maltreatment is a chisel that shapes a brain to contend with strife, but at the cost of deep, enduring wounds.”  He identifies four abnormalities associated with abuse:

1.  Limbic irritability:  the limbic system within the cerebrum is easily disturbed or stirred up.  This results in a variety of symptoms that resemble epilepsy in the temporal lobes of the cerebrum such as: headache, tingling, numbness, dizziness & vertigo, staring, twitching, autonomic symptoms (flushing, shortness of breath, nausea, feeling of being on an elevator), visual hallucinations (patterns, geometric shapes, flashing lights, size or shape distortions), auditory hallucinations (ringing, buzzing, repetitive voice), taste & smell hallucinations (foul, unpleasant tastes or odors), sensation of something on or under the skin, deja vu (“this has happened before”), jamais vu (the familiar seems unfamiliar), watching own actions as observer, abrupt mood changes with no apparent cause that also cease abruptly.  Not all of these will necessarily occur; they are just examples of what can occur.

The increased limbic irritability sets the stage for problems later on in life:

• panic disorder
• Post-traumatic stress disorder (PTSD)
• increased hormonal responses to stress (= hypervigilance)
• risk for dissociative symptoms
• memory impairments
• Attention Deficit Hyperactivity Disorder (ADHD)-like symptoms

2.  Deficient development and differentiation of left cerebral hemisphere: the right hemisphere grows as in non-abused children, but the development of the left hemisphere development lags.  In non-abused children, there is more rapid growth of the left hemisphere than the right from 2-10 years of age,  This results in the left hemisphere being larger than the right.  In abused children, the left is smaller than the right.

The left hemisphere is the location of the language center in most people, so language ability is impaired and neuropsychological testing shows decreased verbal performance.  There are abnormalities in the left hemisphere that are seen in an EEG.

The hippocampus, the structure critical to storing or retrieving memories, is one of the few areas of the brain to add new neurons after birth.  The cells of the hippocampus have an unusually large number of receptors for the stress hormone cortisol.  High cortisol concentrations from stress therefore have a toxic effect on the developing hippocampus, slowing down development.  A decrease in the size of the hippocampus proportional to the severity of symptoms was found in one study: the left hippocampus was found to be 12% smaller in people with PTSD than in controls (and the right hippocampus was of normal size).  This results in decreased verbal memory scores on tests.  This is a permanent alteration: it persists into adulthood.

3.  Deficient integration between the left and right hemispheres: the corpus callosum is the structure that connects the left and right halves of the cerebral cortex.  The left hemisphere is specialized for perceiving and expressing language and the right for processing spatial information and also expresses negative emotions.  In adults who were abused as children the left hemisphere shows activity with remembering neutral events while the right shows activity when remembering abuse.  In contrast, adults not abused as children, both left and right hemispheres become active when remembering.

Neglect of boys has the most profound effect on this lateralization of memories while experience of sexual abuse has the most profound effect in girls.

4.  Abnormal activity in the cerebellar vermis (the middle strip between the two halves of the cerebellum): this structure appears to regulate emotional balance, attentional balance, and limbic system activity.  This is one of the few areas of the brain to add new neurons after birth.  Like the hippocampus, the cells also have an extraordinarily high density of cortisol receptors, so and increase in stress results in a decrease in development of the vermis.  The decreased development results in an increased risk of:

• depression
• manic depression
• schizophrenia
• autism
• ADHD

due to a decrease in the ability of the cerebellum to regulate the irritability of the limbic system,

There are some nonhuman primate studies that show that movement of a baby stimulates the cerebellum to grow, particularly the vermis, and that babies who are not moved are severely damaged.  In people, this lack of movement as a baby reflects a lack of maternal attention (neglect) that leads to a lifelong change in the production of two brain hormones: oxytocin production is decreased while vasopressin (also called anti-diuretic hormone or ADH) is increased.

Oxytocin is the hormone released by a woman giving birth.  It is also responsible for the subjective feeling of love and maintaining monogamous relationships.  It is also the hormone involved in the climax and release of sexual response.  A decrease in the production of oxytocin is linked to a diminished capacity for sexual fulfillment and a decreased commitment to a single partner.

Vasopressin (ADH) is a stress hormone that increases blood pressure and conserves water in the kidneys.  It also increases sexual arousal, but is not involved in sexual climax (oxytocin is).

These two effects together (low oxytocin + high vasopressin production) result in:

•  increased risk of depression with chronic, low-level unhappiness
•  increased risk of anxiety, panic disorder, PTSD, hypervigilance, negativity, suspiciousness, dissociation impaired memory
•  increased risk of ADHD-like symptoms, such as impulsiveness
•  rapid shifts from the logical left cerebral hemisphere to the right cerebral hemisphere with its highly negative, critical emotional state (the two opposing views of abuser stored in separate hemispheres and remain unintegrated)
•  aggression and violence directed toward self or others

Once an adult, a person is unlikely to be able to reverse all these changes in development and processing.  Managing in spite of them can take a superhuman effort.  Therefore, it is critical to prevent the damage that results from abuse of children.

If you are interested in this topic, please see the original paper for more details and sources for the information.  This is my summary of the information presented in the paper, not the original paper itself.