Latest research has brought to light that parasites present in the brain are capable of modifying its functions. The parasite in question is toxoplasma gondii and it resides in the brain, according to the present research, in 10% to 20% of UK population. Researchers from the University of Leeds undertook the study and the results were profound. The study found that dopamine, which is an important chemical messenger in the brain, is modified by these parasites. Although there have been proofs that parasites cause irregular behavior in small insects such as ants, this is the study that shows that parasites are capable of manipulating brain function in mammals as well.
Dopamine is a very important chemical in the brain and irregular functioning of this chemical is the known reason for mental disorders such as Parkinson’s disease, schizophrenia and ADHD (Attention Deficit Hyperactivity Disorder). The present study has been undertaken on rodents and is the first such study on mammals. It has come to light that these parasites are capable of manipulating the functions of the brain and cause behavioral changes in the creatures. It was found that rats lost fear of cats, their biggest predators. This aided the parasites to reach the bodies of cats when rats fearlessly faced cats and were eaten by them. The parasites begin their lives in cats and this is their way of completing their life cycle. 
The research found that in the cells that hosted the parasite, the amount of dopamine released was much higher than the normal cells. Dopamine if the chemical that is responsible for sending messages to various parts of the body in order to control movement, behavior and cognition. The chemical is also responsible for controlling emotions such as fear and pleasure. It triggers emotions that make a person seek sensational experiences. When dopamine is deficient in the body, Parkinson’s disease is a common occurrence.
Dr. McConkey and his group of researchers found that dopamine is encoded by the parasite and controls its release and function. The lead researcher said that the research has made it clear that T.gondii has the ability to manipulate and orchestrate behavior in mammals by causing a significant increase in the amount of dopamine released. He also said that humans are not the main hosts for the parasite and only come by accidentally. There is no specific place in the brain that they attack. Behavior changes in humans can vary from one person to another depending on the area of the brain that they attack. The next study of the researcher will focus of tracing the functioning pathway of the parasite.