Obsessive Behavior and the FKBP12 Gene
December 22, 2008 by Kristina Chew, PhD
Filed under Health
“Restricted, repetitive, and stereotyped patterns of behavior, interests, and activities”—-these are noted in one of the DSM-IV criteria for Autism Spectrum Disorder. A study published in the December 10th Neuron has found that reducing the activity of the gene FKBP12 in the brains of mice affected their synapses, and increased obsessive behavior and “fearful memory.” As noted in today’s Science Daily:
The protein FKBP12 regulates several important cell signaling pathways, and decreasing its activity enhances long-term potentiation in the hippocampus, said Dr. Susan Hamilton, chair of molecular physiology and biophysics at [Baylow College of Medicine] and a senior author of the report. (Long-term potentiation means the enhancement of the synapse or communication between neurons.)
It accomplishes this by fine-tuning a particular pathway called mTOR signaling (mammalian target of rapamycin). The mice in whose brains the activity of the gene was reduced had longer memories and were more likely to exhibit repetitive behaviors than normal mice.
Researchers suggest that their findings might lead to the develop of drugs for autism and also for obsessive compulsive disorders.
Although—-what about the use of such repetitive actions to calm and self-soothe?
If we’re talking about “fearful memory” here, then this probably applies to OCD, but not to autism. OCD is an anxiety disorder, and the repetitive behaviors in OCD are meant to reduce anxiety. To somebody with OCD, they’re embarrassing and time-consuming; but every time a repetitive behavior calms anxiety, it reinforces the activity.
That’s far different from the calming, entertaining, and generally pleasurable effect an autistic person gets from stimming or engaging in special interests. For those, I think you’d have to look at both sensory processing and the processing of pleasure and reward. Longer “fearful memory” may occur in autistics more often, but only incidental to the prevalence of PTSD.
Now, if we could get mice which deliberately sought out certain sensations (it’s not unknown in animals–one of my cat likes making sounds by scraping his paws across things; another loves to lick fabric)… then I might think we had a model for stimming in autism.
Martijn Dekker once pointed out a very sensible metric by which to distinguish OCD obsessions from autistic fixations: OCD obsessional thoughts are *unwanted* by the person thinking them, but autistic fixational thoughts are pleasurable and *wanted* by the person thinking them.