Insula cortex prevents withdrawal symptoms in rats. Insula cortex may be a key structure in decision making
Scientists have identified a brain region that is essential for experiencing drug cravings. The team hopes that discovery could lead to the use of medicines to shut down the region and diminish craving. The insular cortex or insula lies deep in the brain and is involved in perceiving the body’s needs and emotions.
Chemical injection
The research team injected a chemical into the brains of amphetamine-addicted rats that temporarily stopped activity in the insula.
Before the injection, the rats were given the choice of entering two interconnected chambers — one brightly lit and with amphetamines on tap; the another dark but with salty water on tap.
The addicted rats preferred the light chamber even though rats normally prefer dark places.
But when their insula had been shut down they reverted to a preference for the dark chamber.
“Our finding indicates that this region of the brain processes information about the physiological states of the body and may guide behaviour,” said Fernando Torrealba of the Pontifical Catholic University in Santiago, Chile.
The team went on to show that the insula is important in transmitting a feeling of general malaise to the rest of the brain.
The researchers injected rats with lithium chloride, a drug which makes the animals feel unwell and largely stop moving. But rats that had previously received the insula-blocking injection behaved normally.
Symptom prevention
This supports the idea that in the drug addiction case, the insula is preventing the animals from experiencing withdrawal symptoms.
“This showed us that the [insula] not only informs the rest of the brain about craving, but also the signs of gastrointestinal discomfort, and that this information about bodily states may guide behaviour,” said Dr Torrealba.
“Since this region serves the perception of bodily needs and emotions, it may be a key structure in decision making by informing the executive prefrontal cortex of our needs as in the case of drug abuse.”
The team, writing in the journal Science, suggest that a treatment that prevented the insula from firing in humans might take away the craving experienced by drug addicts.
Insula activity
“The modulation of insula activity using non-invasive approaches should be considered as a therapeutic target to alleviate the craving for drugs of abuse,” the team argues.
Other research suggests that the insula may play a similar role in humans. Studies have shown that the insula is activated by feelings of disgust triggered by unpleasant odours or observing disgusted facial expressions on other people.
Another study showed that patients who suffered damage to the brain region were easily able to quit smoking.
Guardian Newspapers Limited 2007
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