What Part of the Brain Controls Emotions?

Even though we think of emotions as internal states, psychologists define emotions as a combination of cognitions, feelings and actions. This means what we think of as "emotions" includes not only how we feel, but also how we process and respond to those feelings.

To understand this, it's helpful to consider the purpose of emotions. In 1872, Charles Darwin first published "The Expression of the Emotions in Man and Animals," which established that emotions serve an important evolutionary purpose. In order for a species to continue, it needs to survive and pass on its genetic information.

Emotions like fear serve to protect you from danger so you can survive to pass on your genes. The "fight or flight" response that primes your body to defend itself or run away from danger is also an emotional reaction. Emotions like love and lust give you the desire to reproduce.

For these reasons, the brain takes on the function of evaluating a stimulus — such as a dog that's about to attack or an attractive person batting their eyelashes — and crafting an emotional response to it. The brain "thinks" in terms of how it can best respond to a situation in order to survive and reproduce, and it uses emotions as the catalyst to convince the rest of your body to act accordingly.

Without Words for Emotions

Emotions serve an important function, but what if you were unable to identify yours? For some people, the inability to realize when they're experiencing emotions is a reality. People with alexithymia (Greek for "without words for emotions") have trouble identifying internal emotional states and describing their emotions to others.

Your brain is a complex network that processes vast quantities of information every second. Part of the brain's information-processing network includes neurons, or cells that transmit signals throughout the brain.

Neurons send signals through neurotransmitters, which are chemicals some release and others receive. These chemicals essentially let the parts of the brain communicate with each other.

The three most commonly studied neurotransmitters are dopamine, serotonin and norepinephrine:

Abnormalities in how the brain receives and processes these chemicals can have a big effect on your emotions. For example, when you do something rewarding or pleasurable, the part of your brain that processes that information interacts with the chemical dopamine.

If your brain can't receive dopamine normally, the result is that you feel less happy — or even sad — after what should have been a happy experience. Studies of people with major depressive disorder (MDD) have shown that they have fewer serotonin receptors in their brains [source: National Institutes of Mental Health].

Antidepressants and Your Brain

Because neurotransmitters have such an impact on your emotions, tweaking the amounts of certain brain chemicals can help relieve symptoms of depression. That's how most antidepressants work — they change how much of a certain brain chemical your brain gets.

Some do this by reducing the reuptake (reabsorption into the neuron it was released from) of serotonin, dopamine, norepinephrine or a combination of these chemicals, which raises their levels in your brain and improves your mood [source: Mayo Clinic and Licinio].

Your brain is made up of many different parts that all work together to process the information it receives. The main part of the brain responsible for processing emotions, the limbic system, is sometimes called the "emotional brain."

The Amygdala and Fear Response

Part of the limbic system, called the amygdala, assesses the emotional value of stimuli. The amygdala is the main part of the brain associated with fear reactions — including the "fight or flight" response. A person who has a seizure in the temporal lobe (the location of the amygdala) sometimes reports an intense feeling of fear or danger.

The Dopamine Center

The part of the brain stretching from the ventral tegmental area in the middle of the brain to the nucleus accumbens at the front of the brain has a huge concentration of dopamine receptors that make you feel pleasure.

The Hypothalamus and Emotional Regulation

The hypothalamus is in charge of regulating how you respond to emotions. When excitement or fear causes your heart to beat faster, your blood pressure to rise and your breathing to quicken, it's the hypothalamus doing its job.

The Hippocampus and Memory

The hippocampus turns your short-term memory into long-term memory and also helps you retrieve stored memory [source: BBC]. Your memories inform how you respond to the world around you, including what your emotional responses are.

Because different parts of the brain process different emotions in different ways, injury to any part of the brain can potentially change your moods and emotions.

The Limbic System: Afraid of Everything?

The limbic system was one of the first areas in the human brain to develop. Even though the brain has since evolved to have more complex functions, the function of the limbic system itself is still fairly primitive. Its responses to stimuli are still simple and generalized.

Because the limbic system regulates the emotions, your emotional responses are also often simple and generalized.

For example, even though other parts of your brain can reason that only certain snakes are dangerous, the limbic system can't differentiate among snakes, so you might respond with fear when you see any snake, whether or not it's dangerous.

If you were to crack open your skull and take a look at the gray matter contained within it, you'd see that the brain appears to be divided into two equal-sized halves. These are your brain's hemispheres and, while they work together to keep you functioning, they each take responsibility for processing different types of information.

The left side of your brain thinks in concrete ways, such as the literal meaning of words and mathematical calculations, while the right side thinks in more abstract ways, such as symbolism and gestures.

Because the two sides of your brain process information differently, they work together to keep your emotions in check.

Here's an easy way to explain it: The right hemisphere identifies, and the left hemisphere interprets. The right brain identifies negative emotions, like fear, anger or danger. It then alerts the left brain, which decides what to do by interpreting the situation and making a logical decision about how to act in response.

It's a great system, unless something happens and one side of the brain can't do its job. Without the left brain, the right brain would be overcome with negative emotions and not know how to respond to them. And without the right brain, the left brain would not be as good at identifying negative emotions.

When One Side of the Brain Takes Over

Scientists have actually seen firsthand what happens when the system of emotional balance provided by the brain's hemispheres breaks down. They've found that people who have had brain damage in the left hemisphere of the brain are at a higher risk for suicide because they're overwhelmed with negativity, while people who have had damage to the right hemisphere can be overly optimistic because they have trouble identifying negative emotions.

It may seem like common sense: Recalling a negative memory can put you in a bad mood, and thinking about a happy memory can put you in a good mood. But there's actually scientific evidence to back that up. Studies even show that this effect is taking place whether or not we're aware of it.

So what's the big deal? It turns out that memory recall can be used to regulate mood in people who are experiencing depression, because thinking about positive memories causes the brain to release dopamine. So when someone tells you to cheer up, it may be a simple matter of thinking happy thoughts [source: Gillihan].

Not surprisingly, memories of previous experiences influence how you respond emotionally to situations. If you once nearly drowned, you might experience fear around water. If a previous love had a wandering eye, you might feel jealousy when a current flame looks at another person.

What's more, the intensity of the previous experience affects the intensity of the current emotion. For example, a soldier who has had extensive combat experience or traumatic combat experience will likely have more intense anxiety later on.

Preconceived ideas also affect your emotions. Anticipation and your expectations, which are driven by memories of previous events, affect the intensity of an emotional reaction [source: Frijda].

Memory and the Hippocampus

The main part of your brain associated with storing these emotion-affecting memories is the hippocampus — a small, seahorse-shaped part of the limbic system.

If you were to damage your hippocampus, you wouldn't be able to store any new memories, and you might even lose access to some of your old memories [source: BBC]. As a result, damage to the hippocampus can have a pretty big impact on your emotions and how you respond to the world around you.