Neuropathology of Bipolar Disorder

Doctor Ellen Leibenluft discusses brain regions associated with bipolar disorder, including the amygdala (which may be smaller) and prefrontal cortex (which may have different activity).

There is increasing attention being paid to the brain regions that are dysfunctional in bipolar disorder - bipolar disorder both in children and in adults. It appears that one important region is the amygdala, which is a little area in our brain; 'amygdala' means 'almond' in greed. It’s inside our temporal lobes so the amygdala is located in the brain, and it is important in terms of identifying in the environment what's important to us emotionally. If we see danger for example, the amygdala will become activated. If we see anything that we consider to be very rewarding, the amygdala will become activated. There is some evidence in both adults and children with bipolar disorder that the amygdala tends to respond more in people with bipolar disorder than it does in people without bipolar disorder, so that maybe the brains of people with bipolar disorder are seeing the world as more emotional than are people without bipolar disorder. There is also evidence in children with bipolar disorder that the amygdala is smaller than it should be. In adults, it’s more of a mixed literature, some studies say it’s too small, some say it’s too big, but in children it seems that it’s pretty clear that it’s likely to be too small. Other parts of the brain that people have been very interested in bipolar disorder include the prefrontal cortex. The prefrontal cortex has many different parts but the two parts of interest are the so called dorsal lateral prefrontal cortex and the ventral prefrontal cortex. The ventral prefrontal cortex is very tightly connected to the amygdala, and like the amygdala deals with what’s rewarding and what isn’t rewarding in our environment. There is some literature and some data that like the amygdala, the ventral lateral prefrontal cortex may be too active at times in people with bipolar disorder. On the other hand the dorsolateral prefrontal cortex is the part that’s kind of the rational part; it’s the part that figures out what’s going on in the world and figures out how can we best strategize to get what we want. There’s some evidence that that’s less active in people with bipolar disorder than in people without. So putting it all together, you’ve kind of got a situation where the emotional parts of the brain may be particularly active in people with bipolar disorder, and the part of the brain that supposed to sort of damp down the emotional parts of the brain may be a bit less active in people with bipolar disorder.