Exactly what VENs are doing within this critical circuit is not yet known, Allman said. But they are in the catbird seat for turning feelings and emotions into actions and intentions.
The human insula, with its souped-up anatomy, is also important for processing events that have yet to happen, Paulus said. "When you decide to go outside on a cold day, your body gets ready before you hit the cold air," he said. "It starts pumping blood to where you need it and adjusts your metabolism. Your insula tells you what it will feel like before you step outside."
The same goes for drug addicts. When an addict is confronted with sights, sounds, smells, situations or other stimuli associated with drug use, the insula is activated before using the drug.
"If you give cocaine to an addict, you are affecting their brain's reward system, but this is not what drives the person to keep using cocaine," Paulus said. The craving is what gets people to use.
Grand plans
For example, smokers enjoy whole-body effects, said Nasir Naqvi, a student at the University of Iowa Medical Scientist Training Program, who was the lead author of the recent article on smoking. It is not just nicotine binding to parts of the brain, he said, but sensations — heart rate, blood pressure, a tickle in the lungs, a taste in the mouth, the position of the hands, all the rituals.
The insula's importance makes it an ideal target for many kinds of treatment, Paulus said, including drugs and sophisticated biofeedback. But methods to quell insular activity must be approached carefully, he said. People might lose the craving to smoke, drink alcohol or take other drugs, but they could simultaneously lose interest in sex, food and work.
As clinicians explore the possibilities, Craig is thinking about the insula in grander terms.
For example, lesions in the frontal insula can wipe out the ability to appreciate the emotional content of music. It may also be involved in the human sense of the progress of time, since it can create an anticipatory signal of how people may feel as opposed to how they feel now. Intensely emotional moments can affect our sense of time. It may stand still, and that may be happening in the insula, a crossroads of time and desire.
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