What's the difference between noticing the rapid beat of a popular song on the radio and noticing the rapid rate of your heart when you see your crush? Between noticing the smell of fresh baked bread and noticing that you're out of breath? Both require attention. However, the direction of that attention differs: it is either turned outward, as in the case of noticing a stop sign or a tap on your shoulder, or turned inward, as in the case of feeling full or feeling love.
Scientists have long held that attention – regardless to what – involves mostly the prefrontal cortex, that frontal region of the brain responsible for complex thought and unique to humans and advanced mammals. A recent study by Norman Farb from the University of Toronto published in Cerebral Cortex, however, suggests a radically new view: there are different ways of paying attention. While the prefrontal cortex may indeed be specialized for attending to external information, older and more buried parts of the brain including the “insula” and “posterior cingulate cortex” appear to be specialized in observing our internal landscape.
Most of us prioritize externally oriented attention. When we think of attention, we often think of focusing on something outside of ourselves. We "pay attention" to work, the TV, our partner, traffic, or anything that engages our senses. However, a whole other world exists that most of us are far less aware of: an internal world, with its varied landscape of emotions, feelings, and sensations. Yet it is often the internal world that determines whether we are having a good day or not, whether we are happy or unhappy. That’s why we can feel angry despite beautiful surroundings or feel perfectly happy despite being stuck in traffics. For this reason perhaps, this newly discovered pathway of attention may hold the key to greater well-being.
Although this internal world of feelings and sensations dominates perception in babies, it becomes increasingly foreign and distant as we learn to prioritize the outside world. Because we don’t pay as much attention to our internal world, it often takes us by surprise. We often only tune into our body when it rings an alarm bell –– that we’re extremely thirsty, hungry, exhausted or in pain. A flush of anger, a choked up feeling of sadness, or the warmth of love in our chest often appear to come out of the blue.
In a collaboration with professors Zindel Segal and Adam Anderson at the University of Toronto, the study compared exteroceptive (externally focused) attention to interoceptive (internally focused) attention in the brain. Participants were instructed to either focus on the sensation of their breath (interoceptive attention) or to focus their attention on words on a screen (exteroceptive attention). Contrary to the conventional assumption that all attention relies upon the frontal lobe of the brain, the researchers found that this was true of only exteroceptive attention; interoceptive attention used evolutionarily older parts of the brain more associated with sensation and integration of physical experience.
Exteroceptive attention relies on the frontal lobes of the neocortex (literally, “new” cortex), the evolutionarily newest outer layer of our brains that most distinguishes humans from other species. Interoceptive attention, however, relies upon brain regions that link the cortex to the limbic system, an evolutionarily older brain system that we share in common with many other animals. These limbic connections may support more direct access to emotions and physical sensations while the neocortex is more responsible for a conceptual sense of self. By recruiting “limbic-bridge” areas like the insula and posterior cingulate, a person using interoceptive attention may bypass the pre-frontal neocortex, directly tapping into bodily awareness that is free from social judgment or conceptual self-evaluation.