Changes in the Bipolar Brain

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Two strategies have been used to investigate how bipolar disorder affects the brain: examination of brain tissue after people with bipolar have died and brain imaging in people who have bipolar disorder. Unfortunately, few studies of either type have been performed.

Reported Changes in the Bipolar Brain:

- Decreases in the number and density of glial cells in the prefrontal cortex.

- Decreases in the number of neurons in part of the hippocampus.

- Increases in the levels of some neuropeptides in the hypothalamus.

- White matter hyperintensities: small abnormal areas in the white matter of the brain (especially in the frontal lobe) as seen using magnetic resonance imaging. These abnormalities may be caused by the loss of myelin or axons.

- Decreases in the size of the cerebellum.

- Reduced activity in the prefrontal cortex during the depressive stage.

Methods of Brain Imaging:

Recent technology has enabled neuroscientists to "see" inside the living brain. These brain imaging methods help neuroscientists:

1. Understand the relationships between specific areas of the brain and what function they serve.

2. Locate the areas of the brain that are affected by neurological disorders.

3. Develop new strategies to treat brain disorders.

Computed Tomography Scan (CT scan)

CT scans use a series of X-ray beams passed through the head. The images are then developed on sensitive film. This method creates cross-sectional images of the brain and shows only the structure of the brain, not its function.

Positron Emission Tomography (PET)

A scanner detects radioactive material that was injected or inhaled to produce an image of the brain. Commonly used radioactively-labeled material includes oxygen, fluorine, carbon and nitrogen. When this material gets into the bloodstream, it goes to areas of the brain that use it. So, oxygen and glucose accumulate in brain areas that are metabolically active. When the radioactive material breaks down, it gives off a neutron and a positron. When a positron hits an electron, both are destroyed and two gamma rays are released. Gamma ray detectors record the brain area where the gamma rays are emitted. This type of method provides a functional view of the brain.

Advantages:
Provides an image of brain activity.

Disadvantages:
Expensive to use.
Radioactive material used.

Magnetic Resonance Imaging (MRI)

MRI uses the detection of radio frequency signals produced by displaced radio waves in a magnetic field. It provides an anatomical view of the brain.

Advantages:
No X-rays or radioactive material is used.
Provides detailed view of the brain in different dimensions.
Safe, painless, non-invasive.
No special preparation (except the removal of all metal objects) is required from the patient. Patients can eat or drink anything before the procedure.

Disadvantages:
Expensive to use.
Cannot be used in patients with metallic devices, like pacemakers.
Cannot be used with uncooperative patients because the patient must lie still.
Cannot be used with patients who are claustrophobic (afraid of small places). However, new MRI systems with a more open design are now available.

Functional Magnetic Resonance Imaging (fMRI)

Functional MRI detects changes in blood flow to particular areas of the brain. It provides both an anatomical and a functional view of the brain.

Angiography

Angiography involves a series of X-rays after dye is injected into the blood. This method provides an image of the blood vessels of the brain.

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