OCD From a Neurobiological Standpoint
An obsession represents a filtering problem. Our frontal cortex runs the brain circuits that help us with ‘hypothetico-deductive reasoning’. In other words, it helps us find answers when there is a limited amount of information available. It is able to ‘fill in the blanks’ with our own predetermined thought patterns about who or what we are considering. This part of our mind is conscious and has unconscious filters (actually learning processors) that help establish and protect our thought patterns. One such filter is the cortico-striatal-thalamo-cortical circuit. As you may be able to tell it is named for each brain structure it enlists.
The thalamus is the brain structure that acts as the first major processing center for nearly all sensory information as it makes its way to our cerebral cortex. Every little sensory neuron (sight, sound, taste, smell, touch, temperature, kinesthetic, pain, balance and internal sense) reaches its axon to the thalamus which sits between the cerebral cortex and the midbrain. This very interesting structure has many functions, one of which is to act as a focal point for circuits that initially process and allow sensory information into the amygdala and the cerebral cortex. Another function, the one we are interested in today, is to REFINE this information through learning circuits that keep information traveling back and forth between the frontal cortex (highest mind) and the thalamus until it allows this processed information to pass through in either direction. These circuits are called the striatum and the direct circuits amplify throughput and the indirect circuits filter throughput.
Like the rest of the brain, the information is kept separated as it travels along. The information stops at a structure like the thalamus at very specific nuclei to be processed and then sent on. The striatum carries the same organizational architecture. Circuits within the striatum hold their position until they reach their correct destination either to a nuclei in the thalamus or a specific part of the cerebral cortex. Rather than thinking of this as ‘traveling from here to there’, it is likely more correct to think of it as ‘messaging the signal’ along the way.
One portion of the striatum, called the sensory-motor circuit, travels from the putamen to the sensory and motor cortex. Difficulties along this circuit are thought to cause Tourette’s syndrome. The Dorsal Cognitive circuit travels from the dorsal portion of the caudate to the dorsal lateral prefrontal cortex with difficulties here potentially relating to ADHD. There also exists as an emotional circuit along the ventral striatum. Currently we are interested in OCD and difficulties along the ventral-cognitive circuit which carries socially relevant and emotionally charged information. It travels from the ventral portion of the caudate nucleus to the anterolateral prefrontal cortex.
What Neurobiology and OCD Means for You
So, why do I tell anyone about that! I do this so that those who suffer OCD can know that this isn’t ‘all in their head’. Neurobiology and OCD are connected. The brain is real.It has a top and a bottom. It really is the place where we think and feel, and like the rest of the body, it doesn't always function perfectly. These symptoms are not a part of why you are, they are a group of poorly connected neurons that are trying to take over.
Also, obsessions and compulsions seem really weird. They make no sense! Being sad can make some sort of sense at least sometimes. But, opening and closing a door three times in a very particular way, over and over ‘until we get it right’ makes NO SENSE. That’s right! It doesn’t. When there is ‘slippage’ in the function of this striatal circuit, information gets through to the cortex and our conscious mind, that has no business being there. NONE.
You see, neurons only survive when they connect and talk to other neurons. But, that’s a problem for the neurons that deliver this useless information. We lose more than one half of our neurons from birth to thirty with only the neurons that are talking and functionally connected surviving. So these neurons have a problem. They have to recruit more friends through this striatal slippage or die. So they busily convince as many of their friends as they can to join them. These 'friends' are drawn away from cells that refine how we see and respond to life situations therefore we become less capable.
So yes, these obsessions and compulsions are a problem and the problem tends to grow over time. Another more important problem is that the person is ‘losing their grip’ on what is really important to them in life. The small group of cells dedicated to making no sense, are in direct competition with the cells that allow us to experience and express who we are. This is ‘the rest of the story’ regarding neurobiology and OCD.