Rats with brain damage behave like sex addicts despite negative consequences.
New research shows that when damage is induced in the medial prefrontal cortex (mPFC) area of the brain in rats, the rats behave in a manner similar to humans diagnosed with “hyper-sexual disorder.”
Hyper-sexual disorder, commonly referred to as sex addiction, afflicts both men and women, is characterized by compulsive sexual behavior, and also includes behaviors such as excessive masturbation, cybersex, and pornography use. According to the Society for Advancement of Sexual Health, up to 3-5% of the population may be affected. Compulsive sexual behavior is also often associated with other psychiatric conditions, including bipolar disorder and substance abuse.
The mPFC is an area of the brain that is known to be important in inhibiting destructive or other inappropriate behaviors. Dr. Lique Coolen, Canada Research Chair in the Neurobiology Department of Motivation and Reward, and her team studied whether or not the mPFC might be involved in inhibiting sexual behavior.
Male rats with damage to the mPFC at first exhibited normal sexual behavior compared to rats without damage. The researchers then “taught” both sets of rats a negative association with sex by injecting all the rats with a medicine after mating that induced nausea. The rats learned to associate mating with unpleasant consequences.
After an average of four “lessons,” 78% of the non-damaged rats ceased mating behaviors, even going as far as attempting to avoid female rats entirely. The animals with damage to the mPFC continued to engage in sexual behavior, despite the immediate negative consequence of feeling ill.
These rats did appear to be capable of learning. When the same medication was administered in a specific place, the rats with mPFC damage were able to learn the association and to avoid that location.
Extreme caution must be used in comparing studies of animal behavior with human behavior. But Coolen’s research suggests that the common reaction to reports of celebrity sex addiction as simply “an excuse for bad behavior,” may be a misconception. Sex addiction may not warrant the bad press it receives.
Damage to the brain itself may not be necessary to cause the rats’ inability to control their sexual impulses. It may be that more subtle differences, such as alterations in brain chemistry or changes in neuronal connections are enough to trigger sexual compulsion in rats. Such differences may be more amenable to future potential treatment.
While it is unknown if these results are applicable to humans, this study may help scientists to better understand other disorders involving impulse control. The next steps in research might focus on understand what the actual chemicals are that are important for the function of the prefrontal cortex in inhibiting these behaviors.
Dr. Lique Coolen’s research will be published in the June issue of Biological Psychiatry.
Primary source: Elsevier