A mental illness can be defined as a health condition that changes a person's thinking, feelings, or behavior

When someone gets an infection, most people think it's the immune system kicking into gear when they feel some of the body's natural defenses

According to a new study by Harvard University, a small population of neurons near the base of the brain can induce symptoms of sickness

The nervous system talks to the immune system to figure out that the body has an infection and then orchestrates a series of behavioral and physiological alterations

The neurons, which have not been previously described, are found in an area of the hypothalamus

The researchers found these neurons have receptors that are capable of directly detecting molecular signals coming from the immune system

"It was important for us to establish this general principle that the brain can even sense these immune states," said Jessica Osterhout

The researchers found that the key area of the hypothalamus is located right next to a permeable section of the brain called the blood-brain barrier