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Obsessive-Compulsive Disorder (OCD) – Neurobiology

What causes OCD?

OCD is associated with pervasive disruptions in frontal subcortical circuitry.

OCD is associated with pervasive disruptions in frontal subcortical circuitry.

Researchers have had much recent success in elucidating the neural circuitry involved in obsessive-compulsive disorder (OCD).  Advances in functional neuroimaging have identified robust alterations in neural activity within particular functional circuits in individuals with the disorder (Graybiel & Rauch, 2000).  Specifically, OCD is associated with pervasive disruptions in frontal subcortical circuitry (Luxenberg et al., 1988; Robinson et al., 1995).  Before we discuss abnormalities in this circuitry related to OCD, it is worth reviewing the generalities of this neural system.

Frontal subcortical circuitry in OCD


According to Tekin and Cummings (2002), frontal subcortical circuits share several commonalities.  They often “originate in prefrontal cortex, project to the striatum (caudate, putamen, ventral striatum), connect to the globus pallidus and substantia nigra and from there connect to the thalamus.  There is a final link back to the frontal cortex [such that] each circuit forms a closed loop” .  The prefrontal cortex (PFC) can be subdivided into several regions including the dorsolateral prefrontal cortex (DLPFC), the orbitofrontal cortex (OFC) and the anterior cingulate cortex (ACC); and these subregions are involved in separate circuits (the DLPF circuit, the OF circuit, and the AC circuit, respectively).

These circuits have been implicated in various functional tasks.  Individuals with dysfunction in DLPFC areas often exhibit deficits in attention, reasoning, and mental flexibility.  Damage to OFC has been associated with personality changes including behavioral disinhibition and impaired judgment (Tekin & Cummings, 2002).  Work by Damasio and colleagues (1996; 1990) indicates that insults to OFC result in deficits in reward expectancies and preferences.  The ACC is closely interconnected with the limbic system and is thought to support motivation and affective behavior.  Due to its association with motor cortex, the ACC presumably mediates emotionally-motivated movement.  Together, the ACC and OFC influence the emotional value of stimuli and the selection of behavior based on possible reward.

Saxena and Rauch (2000) have suggested that excess positive feedback within frontal subcortical circuits might drive the repetitive symptoms that characterize OCD.  What evidence supports this theory?  In individuals with OCD, resting hyperactivity within frontal subcortical loops has been observed reliably, and this activity is potentiated by symptom provocation (Saxena, Brody, Schwartz, & Baxter, 1998).  Interestingly, following either successful pharmacologic or behavioral treatment for OCD, this hyperactivity diminishes to normal levels.  Empirical evidence implicating frontal subcortical circuitry in the etiology of OCD also includes work by Kelly (1980) who showed that lesions of the cingulate gyrus can reduce obsessive-compulsive symptomatology, presumably by disrupting interconnectivity between orbito-striatal areas or between frontal cortex and the thalamic nuclei that convey limbic input into this region.  Psychosurgical procedures that interfere directly with striatal circuitry also are effective for ameliorating symptoms of OCD.

Error-related negativity in OCD


Psychophysiological studies looking at a component of the event-related potential known as error-related negativity (ERN) also provide independent evidence of abnormalities in frontal-subcortical circuitry.  ERN has been defined as the negative polarity component of the event-related potential that can be observed 30-150ms following the commission of an error (or, as some have suggested, the violation of expectancies; Donkers & van Boxtel, 2005) on simple reaction time tasks.  This potential largely is due to activity in the ACC.

Electroencephalogram acquired from electrodes placed near the medial-frontal scalp has indicated that ERN magnitudes in individuals with OCD are significantly greater than in controls, suggesting enhanced action-monitoring in OCD (Gehring, Himle, & Nisenson, 2000; Ruchsow et al., 2005).  Using a similar choice reaction time experiment, Johannes et al. (2001) observed shorter P3 latencies and ERN deflections that were enhanced in amplitude and longer in duration in non-medicated, non-depressed individuals with OCD relative to controls.  Hajcak and Simons (2002) subsequently replicated and extended these findings using a subclinical “OCD-like” sample of undergraduates who endorsed a high degree of OCD-relevant behaviors on a measure of OC symptomatology.

Gehring, Himle, and Nisenson (2000) have advanced an intriguing theory regarding the relationship between frontal subcortical hyperactivity and obsessive-compulsive symptoms.  They posit that OCD symptoms arise from hyperactive “error signals” generated by the ACC that represent a mismatch between preferred and experienced internal/environmental states.  In response to this error signal, the system effects changes in behavior.  According to this model, individuals with OCD perform repetitive, compulsive behaviors because they experience large and persistent error signals that manifest affectively as feelings of wrongness.

Compulsive behaviors thus are the means by which the system seeks to reduce the perceived discrepancy between preferred and experienced internal/environmental states.  However, these error signals remain relatively unaffected by changes in environmental context and behavior due to continued ACC hyperactivity.  As a result, individuals with OCD experience persistent feelings of anxiety, doubt, and the urge to engage in behaviors that might neutralize these emotions.  Although this theory remains speculative, it provides an interesting link between abnormalities in frontal-subcortical circuitry and the phenomenology of OCD.

My next post discusses cognitive deficits associated with OCD.

Full references for this page can be found here.

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One Comment

  1. PLEASE HELP My son is now 24. He had OCD symptoms most of his young life.
    Currently he suffers from intrusive, compulsive, thoughts, to ‘do something’ for a promise of “eternal salvation’ (as an example of the purpose, he has to do what ever this thought is)
    That ‘something’ can be anything from standing in a worshiping yoga pose to jumping out a high window. (Which he did – breaking both legs) He now hears a command to hit or kick someone.
    The Doctor said he is truly EGO-DYSTONIC so he always stops himself before impact, then taps the other person. IS THIS AN EXAMPLE of HARM OCD?
    The problem is he jumped out the window 2 & 1/2 years ago, was transferred to NH State Hospital. This Compulsion started when he was started on a new medication.
    The hospital transferred him to the Secure psychiatric Unit (S.P.U.) located as part of the Mens Prison. Touching a guard for any reason, even if its a touch on the shoulder, obeying a thought pray to pray for them; leads to being ‘taken down” . My son has been beat up so many times by the guards, I’ve lost count. He has been in isolation over 18 months. They are supposed to give him time out every day. But they do not. The following is one example of self-harm he endures…. He had a hang nail on his small toe. By trying to remove it, he accidentally removed the whole toe-nail. He had to ‘Make them even so- HE RIPPED OUT ALL HIS FINGERNAILS AND TOENAILS.
    He is on so many different medications. including forced ECT. which only stopped because it induced a grand mal seizure His Dr. said this can’t be OCD because you do not hear commands with OCD. Have you ever heard of anything like this???PLEASE HELP

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