Brain Changes in Bipolar Disorder: Understanding the Neural Basis

There are only two strategies currently used to explore the effects of bipolar disorder on the brain: functional brain imaging (positron emission tomography) and the analysis of postmortem brain tissue. Both methods, however, have produced considerable data on the abnormalities associated with the bipolar brain and its biochemical functions.

Monoamines

• Monoamines are a group of neurotransmitters (chemical messengers) that modulate functions of the brain, including response to stress, pleasure, reward, mood, concentration and attention. Monoamines include dopamine, norepinephrine, epinephrine and serotonin.

Thalamus

• Bipolar patients have an average of 31 percent more monoamine binding sites (signal-sending cells) in the brain's thalamus region (participates in regulatory functioning).

Brain Stem (ventral)

• Bipolar patients have an average of 28 percent more monoamine binding sites in the ventral (anterior side) brain stem (message relay center between brain and spinal cord).

Brain Stem (raphe)

• The raphe nucleus in the brain stem, which is home to serotonin cells, is 40 percent smaller for persons with bipolar disorder. This may contribute to the person's low moods and depressive episodes.

Ventral Striatum

• The ventral striatum of a bipolar person, which aids the brain in processing rewards, has about a 30 percent reduction in grey matter (neuronal cell bodies) and tends to be overactive, which may contribute to the loss of judgment during manic episodes.

Hippocampus

• Bipolar brains show a reduction in neuron-connecting branches in the subiculum of the hippocampus. Because the subiculum aids in the recognition of fear, the reduction may create a constant state of anxiety.