Biology 202

2006 First Web Paper

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Obsessive Compulsive Disorder (OCD) is a disorder where a person is plagued by certain obsessions and as a result is compelled to act out certain compulsions to get relief from those obsessions (4). Approximately 2-3% of the population is affected with OCD (8) and approximately 14% of the population is affected with minor symptoms of OCD (2). The age of onset in childhood is before puberty and in adulthood it is around 20 years old (1).

Obsessions in OCD are constant beliefs or images in people's minds that are illogical and silly, but remain constant because they feel that they have no control over them (4). For example a classic obsession would be that people feel that their hands are not clean enough, but dirty or contaminated by something. They would have this on their mind and become obsessed with it, thinking about it and not being able to get relief from that obsession of germs, dirt, or contamination (3), (4). Compulsions in OCD are behaviors that people feel that they must do many times over again in order to become relieved from something that is bothering them. Therefore, if people have an obsession that they are dirty, then they would have the compulsion of continuously washing their hands even if their hands are raw and bleeding from all of the washing (4). Other examples of compulsions are extreme bathing, checking, counting, organizing, and cleaning (2), (3). These compulsions greatly interfere with people's lives because they are time consuming and do not make them feel good, but people have typical feelings of being fearful, doubtful, or disgusted with themselves and their actions (4).

The people understand that their behavior and thoughts are not normal and they do not want to do or to have them (4), but still they do and as a result they feel frustrated. What makes them have those thoughts and act out those compulsions? It interests me how does OCD start in an individual? Is there a biological cause and is it present from birth or does something happen to the individual? The etiology of OCD is of great interest to researchers, who are trying to figure out answers to many questions. There has been much progress made on figuring out the etiology of the disorder, but the precise etiology has still not been found. One of the tools that is used by researchers is Functional Magnetic Resonance Imaging (fMRI) (3). The way this works is that when a person comes in for testing, he/she is presented with specific physical stimuli such as a sound, a visual stimulus, or a movement by the subject. Then the fMRI can track the increased flow of blood to certain parts of the brain, which occurs when those parts have become activated by the appearance of certain stimuli. This shows up on the scan and can be analyzed (5).

One of the most predominant theories about the etiology of OCD states that there is a problem with the connection between the orbital cortex and the basal ganglia (4). There are many things involved in this relationship and one strong theory believes that there seem to be problems because there is "abnormal metabolic activity" (1) in the orbitofrontal cortex, the anterior cingulate/caudal medial prefrontal cortex, and the caudate nucleus. The interactions between these different parts is called a "cortico-basal ganglia network" (1) and it is believed that these cortico-basal ganglia interactions make up a neural system that is very important in the acquisition of habits and also establishing a fixed routine of performing those habits, which is directly connected to the typical behaviors of OCD where people maintain certain obsessive habits and continue to perform those habits. In this theory, each part of this network has an important contribution to the possible forming of OCD. It is believed that when lesions occur in the orbitofrontal cortex, this affects the ability of planning one's behaviors and also in making decisions. An experiment was done with monkeys where it was observed that the neurons in the orbitofrontal cortex adjust their activity in response to the monkey's motivation towards a certain stimulus. However, when a lesion happens, then the monkey experiences abnormal motivations or preferences towards the stimulus. Therefore, when the monkey is exposed to a specific stimulus, certain autonomic responses become reactivated and in OCD, this reactivation becomes extreme and as a result it continues to compel the repetition of certain behaviors which are present during OCD (1).

The second part of the theory is that there is a very strong connection between the anterior cingulate cortex and the orbitofrontal cortex, where the anterior cingulate cortex sends anatomical connections to the rostral cingulate motor area and then this area sends the connections to the motor cortex. As a result of this strong connection, the orbitofrontal cortex working with the anterior cingulate cortex could possibly influence the emotional value that a person places on a stimulus and also the behavior that the person chooses to respond with (1).

Finally, the third part is the role of the basal ganglia and their possible effect on OCD. In this one part of the network, there are many theories because the basal ganglia are believed to be very important in the possible development of OCD. The basal ganglia are believed to be connected with the neocortex through "parallel loops" (1) of the cortico-basal ganglia network. The loops are thought to run from the neocortex to the basal ganglia and after that to the thalamus, which then goes back to the neocortex. One theory is that these loops are possibly involved in the setting of mental habits and also physical habits that a person performs. If there is something wrong within the loops, then this contributes to a problem with the setting of mental and physical habits which results in the repetition of obsessions and compulsions that a person has with OCD. Another possible theory of the function is that the basal ganglia recode certain inputs into bigger groups called "chunks" (1), which represent actions, and then these "chunks" are organized together, producing a sequence of various behaviors. Before the behaviors are exhibited, priorities are made with regards to the sequence of the various behaviors and the choosing of those behaviors. However, with a problem, these priorities are not made and as a result a person can not move from one prioritized behavior to the next. Therefore, the person becomes stuck with one behavior that can not change, becoming an obsession or compulsion. It is believed that the problems of the cortico-basal ganglia network could arise from brain chemistry that is abnormal, which could then cause OCD. These are all theories about the functioning of this cortico-basal ganglia network; however, there is no actual understanding of the correct and normal working neither of this network with the interaction of the loops and the areas and various functions within nor of the problems that could arise and if they would cause OCD. This is one possible explanation that seems to be one of the main ones where it is believed that the problem lies somewhere within the orbital cortex and the basal ganglia (1).

Another theory is that OCD can occur after a traumatic event, where the serotonin levels in the brain can become imbalanced and cause problems with impulses for functions like thinking. Serotonin is responsible for transporting these impulses to and away from nerves (11). This theory would help to explain why some people may suddenly develop OCD; however, researchers are still trying to figure this theory out precisely (3).

These findings support the statement that we learned in class where "science is about getting things less wrong" (9). The findings are developing past theories further, but do not have the complete answer to many questions. So even though, there seems to definitely be a biological cause of OCD, researchers are not exactly sure of what it is. One question that still persists in my mind is do some people develop OCD in adulthood if they did not have a traumatic incident and no signs of OCD in childhood? If so, then what happened to develop it?

There are treatments available for OCD, where the most common ones are Cognitive Behavioral Therapy (CBT), Medication, or a combination of the two (3). CBT is a form of therapy that is focused on trying to change people's thoughts about their behaviors by changing their behaviors. People work with their therapist and together make up different strategies about how to deal with their obsessions and compulsions, focusing on having people gain back their control (4), (6). Some of the techniques used are: "thought stopping" where something is used to disrupt the thought of the obsession (2), and also "Exposure and Response Prevention" (ERP) (11), where the irrational fears of the people are discussed through exposure and then the compulsive behaviors are also confronted through response prevention (11). Another form of treatment is medication where the medications are selective serotonin reuptake inhibitors (SSRI's) like for example fluoxetine (Prozac) or sertraline (Zoloft) (3). These SSRI's appear to be successful in the treatment of OCD because they seem to reverse the "abnormal metabolic activity" (1) that could be occurring in the cortico-basal ganglia interactions, causing the problems (1) , (7).

WWW Sources:
1)Toward a Neurobiology of Obsessive-Compulsive Disorder ,

2) Disorders- Neurology, Neurobiology, and Psychiatry- University of Newcastle,

3) Stanford Psychiatry Neuroimaging Laboratory: Obsessive-Compulsive Disorder ,
4) Obsessive Compulsive Disorder ,

5) Introduction to FMRI ,

6) A Guide to Understanding Cognitive and Behavioural Psychotherapies,

7) Obsessive-Compulsive Behaviors and Disorders: Symptoms, Treatment, and Support ,
8) Brain Explorer- Focus on Brain Disorders- OCD- Epidemiology ,

9) Biology 202 home page,

10) Anxiety Disorders, Panic Attacks, treated with New Therapy Approach ,

11) Physiological Factors in Obsessive-Compulsive Disorder,


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