There are people who can balance very large stones on top of each other. It is a very unnatural sculpture that looks as if it about to fall. 
The TV presenter Kevin McCloud had a go at it. He stated the blindly obvious, that it was not an easy thing to do. This delicately balanced pile of stones can be a metaphor for how the brain works. Everything in the right place processing and transferring data at the right speed.
The brain is made up of irregular shaped clumps of cells called neurons that often have a special function. These clumps of neurons have been given special names and some of these will be discussed later. These specialised areas may interpret sensory data, move data to other parts of the brain or construct meaning.
For people with OCD the way the sensory data is transformed into meaning is of particular interest. Unless the brain is experiencing something as dramatic as schizophrenia this constructed meaning is generally construed as reality. That is a reality that is communally shared. But what if distorted reality is not as dramatic as schizophrenia. What if there is just a slight tilt to the right. A small tilt due to a tiny imbalance within the brain.
What we do know is that people with OCD have different levels of connectivity to certain parts of the brain. This means traffic between selected parts of the brain flow more often in some places and less in others.
Currently there is a six-lane highway from Brisbane to the Gold Coast that is filled with cars ferrying people and goods all day and all night. At each end of the highway the cities are growing faster than if there was only a two-lane road. The people at the Gold Coast end spend their time building bigger and better shopping centres with more and more palm trees. At the Brisbane end we have the cultural icons of GOMA and leading edge theatre. Each city has its specialisation because of the traffic that flows into each city. The brain operates in a similar manner and if the flow of traffic into the specialised area is significantly changed then the output from the brain will also change.
For people with OCD the key area of the brain that has traffic flow problems is called the default mode network. It is a group of neurons that is used in daydreaming, memory, thoughts about yourself, mind wandering and contemplating the future. It is easy to imagine how malfunctions in this area might construct distorted thinking patterns. The technical summary can be found here. People with OCD demonstrated traffic flow and processing activity problems. That is under and over activity. Similar brain patterns were found in the close family members even if they did not have a clinical diagnosis of OCD. This is a strong indicator that genetics is responsible for how OCD achieves its distorted reality.
OCD is reflected in the physical connectivity of the brain. Even if you don’t have OCD your genetic background has conspired to create a fertile soil where reality can be much more easily distorted.
The default mode network is a target area for treatment for OCD. Here is an new research article on how deep brain stimulation is used to address treatment resistant OCD.
Default network connectivity as a vulnerability marker for obsessive compulsive disorder. Z.W. Peng, T. Xu, Q.H. He, C. Z. Shi, Z. Wei, G.D. Miao, J. Jing, K.O. Lim, X.N. Zuo, and R. C. K. Chan. Psychological Medicine (2014), 44, 1475–1484. © Cambridge University Press 2013 doi:10.1017/S0033291713002250 Image attribution: By User Minesweeper on en.wikipedia - Minesweeper, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1302402
By Leandro Inocencio - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=22166102
Disclaimer: This content is not intended to provide medical or mental health advice. It is intended to stimulate an increased understanding of OCD. The content may not be accurate or express the views of the journal article authors.