Obsessive-compulsive disorder (OCD) is a mental disorder characterized by intrusive thoughts that produce anxiety (obsessions) and repetitive behaviours aimed at reducing the anxiety (compulsions). Symptoms may include repetitive hand-washing, a generalized fear of contamination, extensive hoarding, preoccupation with sexual or aggressive impulses or with particular religious beliefs, aversion to odd numbers, and nervous habits such as repeated opening and closing of doors, constant organizing of objects in certain ways, obsessive counting of events, etc.
OCD may be seen as a result of an imbalance between long-term memory and short-term memory processes. A sufferer may be stuck in a mental loop where long-term memory is in control of the subject’s brain to such an extent that their reactions are solely based on memory without the influence of the input (other than as a trigger for the memory).
Neuroimaging studies show, however, that OCD patients perform considerably better on procedural memory tasks (memory of skills and how to do things) due to over-activation of the striatum brain structures, specifically the frontostriatal circuit. Thus, the procedural memory in OCD patients may actually be improved in its early learning stages.
Although there is no scientific evidence to suggest that people with OCD have any problems with verbal memory (remembering information that has been stored verbally or in the form of words), it has been consistently found that people with OCD show deficits in non-verbal, visual or spacial memory. Also, people with OCD (particularly those whose symptoms involve compulsive checking) tend to have less confidence in their memory than those without OCD, even if this level of confidence is not actually related to their actual performance on memory tasks, and the worse the OCD symptoms are, the worse this confidence in memory seems to be. This may explain to some extent the repetitive nature of many OCD symptoms.
OCD has been linked to abnormalities with the neurotransmitter serotonin, and to miscommunication between the different parts of the brain involved in problem-solving. In normal usage, when a problem or task is identified in the orbitofrontal cortex at the front of the brain, it is dealt with in the cingulate cortex, and the caudate nucleus is then responsible for marking the problem as resolved and removing any worry over it. In OCD sufferers, it is thought that the caudate nucleus may be dysfunctional and so this resolution never occurs, leading to increased worry and a recurring and ever-intensifying loop in behaviour.
Recent improvements in the understanding of the neuroplasticity of the brain may lead to a potential cure for the disorder. If the obsessive-compulsive behaviour is consistently identified as such by the sufferer (so that, instead of thinking “I need to wash my hands”, the patient gets into the habit of thinking “it is my OCD which is making me think that I need to wash my hands”), a neuroplastic rewiring of the brain can be induced over time, so that the caudate can be used to work for, rather than against, the patient, in a constructive manner. Recent trials in this kind of behaviour therapy, sometimes referred to as “exposure and response prevention”, have produced some very positive results.