It’s an astonishingly robust finding:
Smokers with damaged insulas were 136 times more likely to have their addictions erased than smokers with damage in other parts of their brains.
What makes this paper so interesting is that it actually makes sense. The insula has been recognized for more than a decade as a crucial substrate for feeling. It sits at an important neural intersection, and is largely responsible for integrating signals generated by our body – so called “somatic markers” – into mental states. As Antonio Damasio has written (his wife is a co-author on the cigarette paper): “The body contributes more than life support. It contributes a content that is part and parcel of the workings of the normal mind.”
What is this mental content? Damasio has shown that these bodily signals are the essence of our conscious emotions. (William James proposed a similar theory in 1882.) Damasio has chronicled the lives of patients whose brains are missing this intricate body-brain connection, normally due to damage in the VMPO. Although they maintain full sensory awareness of their body, these patients are unable to translate their fleshy sensations into emotions. The pounding of their heart never becomes a feeling of fear. A smile doesn’t cheer them up. Because their mind is deprived of their flesh, they live in a cocoon of emotional numbness.
But back to smoking: how does the insula make us addicted to cigarettes? According to this paper, it detects the bodily rituals associated with smoking – the escalated pulse, the slow inhalation, the slight nicotine rush – and combines them with the idea of a cigarette. When we crave a cigarette what we are actually craving are these bodily changes: they are the emotional core of addiction:
Based on the experiences related by the insula-damaged patients, he suspects that the insula is needed create the feeling that smoking is a bodily need. Bechara notes that other research has suggested that the bodily effects of smoking–particularly the effects on the airways–are a crucial part of the satisfaction smokers get from puffing away. If so, he speculates, smoking cessation therapies such as denicotinized cigarettes may ultimately prove more effective than nicotine patches because they provide physical sensations that stimulate the insula and satisfy the smoker.
That said, I wouldn’t go out and lesion my insula to cure my cigarette addiction. One of Damasio’s most surprising discoveries is that the feelings generated by the body are an essential element of decision-making. Although we typically assume that our emotions interfere with reason, Damasio’s emotionless patients proved incapable of acting “rationally”. After suffering their brain injuries, all began displaying disturbing changes in behavior. Some made terrible investments and ended up bankrupt; others became dishonest and anti-social; most just spent hours deliberating over irrelevant details. According to Damasio, their frustrating lives are vivid proof that rationality requires feeling, and feeling requires the body. Your insula might make you addicted, but it also makes you wise.