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| June 12,2002 – SOSI Abstract Number: 1 Sniffing Your Way To A Psychiatric Diagnosis, Avery N. Gilbert Intermittent Explosive Disorder or IED is a well-defined psychiatric diagnosis characterized by impulsive aggression. IED patients respond to even minor provocations with disproportionately aggressive behavior. In attempting to understand the neurobiology of IED, researchers have noticed that the condition resembles the acquired impulsive aggression of patients with specific brain lesions. Damage to the orbital and medial prefrontal cortex and associated structures, including the amygdala, produces a behavioral pathology similar to IED. Patients with these lesions develop impulsive and aggressive behavior, have little control over their emotions, and are unaware of the implications of their actions. The question arises: Is Intermittent Explosive Disorder a functional impairment of the orbital/medial prefrontal cortex circuit? (Otherwise known as the OMPCC.) To answer this question, psychologist Mary Best and her colleagues examined a group of IED patients and compared them to matched healthy controls. They tested sugjects on several cognitive tests known to be sensitive to OMPCC function. Because OMPCC lesions have previously been linked to impaired odor perception, Best et al., also included a test of odor identification. The results from IED patients differed from those of controls, and indeed looked similar to those known from OMPCC lesion patients. IED patients had a significant bias to judge misjudge pictures of neutral facial expression as “disgusted” and pictures of disgusted faces as “angry”. In the Iowa Gambling Task, IED patient were unable to resist the occasional high payout from stacked decks, and continued to draw from them even though the overall payout from these decks was much lower. IED patients were significantly impaired on the odor identification task. Best et al. believe this deficit to be very revealing, because the neural pathways involved in odor detection and identification include the orbital/medial frontal cortex, i.e., the OMPCC. This bolsters the researchers’ idea that IED is a dysfunction of the OMPCC, which accounts for the cluster of sensory and cognitive deficits. The more we learn about the specific neural circuits involved in processing odor information, the more likely it is we will discover unanticipated links between impaired smell ability and other psychiatric conditions. Perhaps the links will be happier ones—wouldn’t it be interesting if people with excellent olfactory perception had superior performance on measures of creativity, mathematics, or “emotional IQ”? Best, M., Williams, J.M., & Coccaro, E.F. Evidence for a dysfunctional prefrontal circuit in patients with an impulsive aggressive disorder. Proceedings of the National Academy of Sciences USA, 99(12):8448-8453, 2002. |
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