The Bipolar Brain-Part 2: The Fight For Domination…When the Right hemisphere is winning.

In our last post we explored that mania may be caused by the left hemisphere dominating the brain and specific areas of the brain being flooded with energy in the form of neurotransmitters or chemicals in the brain.

Now we will explore how depression may be caused by the right hemisphere dominating the brain. In this case,  specific areas of the brain may receive too much or not enough energy in the form of neurotransmitters or chemicals because the right hemisphere needs that energy to dominate the left.

An interesting theory to note is that the left hemisphere of the brain is responsible for more positive thoughts and emotions, which is why some stages of mania may be a very positive experience (except when the left hemisphere is fighting really hard).  Meanwhile, the right side of the brain is more responsible for negative or fear based thoughts and emotions. Keep this in mind as you read about the brain structures affected by the right hemisphere of the brain dominating the the left hemisphere.


Just like in mania, mood  appears to be caused by the Orbitofrontal Cortex. The orbitofrontal cortex is responsible for things like decision-making and is sensitive to reward and punishment.  When the right side of the brain dominates the left hemisphere it may use all of this energy to punish us because it is teamed up with the amygdala (see Emotion below).  Therefore, we may experience feeling very negative emotions and a loss of interests because our brain is flooded with negative chemicals carrying negative messages. At the same time, because of this battle our brain doesn’t have the resources from the left hemisphere that has more neurons that have chemicals that make us feel good and interested in things.


The seat of emotion and our brains response to fear is in the Amygdala. Some studies have found that the amygdala is larger in the right hemisphere and smaller in the left.  This means the right hemisphere is more receptive to fear based emotions. Therefore, during the battle when the right hemisphere is winning, the amygdala is producing huge amounts of negative fear-based emotions that flood our conscious mind in the pre-frontal cortex which we shall soon explore.


The Hippocampus may be highly inhibited or even not functioning when the right hemisphere takes over. The Hippocampus is responsible for forming, storing and retrieving memory. This part of the brain may be completely cut off from resources during the battle and may even break down because of it.

When are thoughts are moving so slow that we can’t even form sentences…or we can’t think at all…

The structure called the Pre-Frontal Cortex is being inhibited during the battle and lacks the energy and resources to function. The pre-frontal cortex is responsible for analytical thinking, problem solving and all other forms of rational thinking.

Hallucinations and Delusions

This may be very similar as to what takes place during mania. This may be the point where the battle between the hemispheres becomes so intense that it jumbles each message between the messengers called neurotransmitters. The message becomes so chaotic that they are not easy to decode. As a result, the brain can’t see what the eyes see or hear what the ears hear.

The Right Hemisphere can only dominate the left for so long…

If the left hemisphere has energy when it takes control of the right hemisphere in its final battle….we go shooting up into mania or usually hypomania (a milder version of mania.) Then the story of the left hemisphere dominating the right begins all over again.

When Neither Hemisphere is Dominant: Understanding Mixed Episodes

A mixed episode may be what we experience when the left hemisphere and right hemisphere are battling. In the moments the left hemisphere is dominant of energy/chemicals and resources we experience mania. As soon as the right hemisphere gains dominance of energy/chemicals and resources we experience depression. This may take place very rapidly in the brain until one side or the other gains full dominance.  Sometimes the dominance does not happen at all and we just experience the battle until the brain exhausts itself from the fight.