It is often said that the heart is the seat of emotions but this is proven to be a false notion. There are areas in the brain which control our emotions and hence help regulate our mood. Senses tell us what's going on in the outside world, while our emotions exist inside of our body to tell us what these events and circumstances mean. Now emotions are controlled by the levels of different chemicals in our brain and at any given moment, dozens of chemical messengers, or neurotransmitters are active, Researchers believe that it is not just the levels of specific brain chemicals but also nerve cell connections, nerve cell growth and the functioning of nerve circuits which have a major impact on our mood. Since depression is a mood disorder,it is safe to say that the primary focus of this condition lies in the brain.
The purpose of the above paragraph was just to make it clear that it is indeed the brain that is affected in depression and also to give you a basic understanding as to how depression works.
To understand how depression affects the brain,Increasingly sophisticated forms of brain imaging such as
--> Positron emission tomography (PET)
--> Single-photon emission computed tomography (SPECT) and
--> Functional magnetic resonance imaging (fMRI) are used.
These permit a much closer look at the working brain than was possible in the past. An fMRI scan, for example, can track changes that take place when a region of the brain responds during various tasks. A PET or SPECT scan can map the brain by measuring the distribution and density of neurotransmitter receptors in certain areas.Use of this technology has led to a better understanding of which brain regions regulate mood and how other functions, such as memory, may be affected by depression.
Areas of the brain that play a significant role in depression are
--> The Amygdala
--> The Thalamus and
--> The Hippocampus.
Research has shown that the hippocampus is smaller in some depressed people. An fMRI study done by investigators who studied 24 women having history of depression showed that on an average the hippocampus was 9% to 13% smaller in depressed women compared with those who were not depressed. The more bouts of depression a woman had, the smaller the hippocampus.Stress which plays a role in depression, may be a key factor here, since experts believe stress can suppress the production of new neurons (nerve cells) in the hippocampus.Researchers are also exploring possible links between sluggish production of new neurons in the hippocampus and low moods.
There are other parts of the brain affected such as the amygdala and the thalamus. The amygdala is part of the limbic system, a group of structures deep in the brain that’s associated with emotions such as anger, pleasure, sorrow, fear, and sexual arousal. The amygdala is activated when a person recalls emotionally charged memories, such as a frightening situation. Activity in the amygdala is higher when a person is sad or clinically depressed. This increased activity continues even after recovery from depression.The thalamus receives most sensory information and relays it to the appropriate part of the cerebral cortex, which directs high-level functions such as speech, behavioral reactions, movement, thinking, and learning. Research has shown that there is a problem in the thalamus of individuals suffering from depression, but the exact mechanism has not been successfully proven.