In recent years, sci­en­tists have dis­cov­ered the human brain works on pre­dic­tions, con­trary to the pre­vi­ously accepted theory that it reacts to the sen­sa­tions it picks up from the out­side world. Experts say humans' reac­tions are in fact the body adjusting to pre­dic­tions the brain is making based on the state of our body the last time it was in a sim­ilar situation.

Now, Uni­ver­sity Dis­tin­guished Pro­fessor Lisa Feldman Bar­rett at North­eastern has reported finding the epi­center of those predictions.

In an article pub­lished in Nature last week, Bar­rett con­tends that limbic tissue, which also helps to create emo­tions, is at the top of the brain's pre­dic­tion hier­archy. She co-authored the paper with W. Kyle Sim­mons, of the Lau­reate Insti­tute for Brain Research in Tulsa, Oklahoma.

"The unique con­tri­bu­tion of our paper is to show that limbic tissue, because of its struc­ture and the way the neu­rons are orga­nized, is pre­dicting," Bar­rett said. "It is directing the pre­dic­tions to every­where else in the cortex, and that makes it very powerful."

For example, when a person is instructed to imagine a red apple in his or her mind's eye, Bar­rett explained that limbic parts of the brain send pre­dic­tions to visual neu­rons and cause them to fire in dif­ferent pat­terns so the person can "see" a red apple.

Bar­rett is a fac­ulty member in the Depart­ment of Psy­chology and is director of the Inter­dis­ci­pli­nary Affec­tive Sci­ence Lab­o­ra­tory. A pio­neer in the psy­chology of emo­tion and affec­tive neu­ro­science, she has chal­lenged the foun­da­tion of affec­tive sci­ence by showing that people are the archi­tects of their own emo­tional experiences.

In the Nature paper, Bar­rett sum­ma­rized research on the cel­lular com­po­si­tion of limbic tissue, which shows that limbic regions of the brain send but do not receive pre­dic­tions. This means that limbic regions direct pro­cessing in the brain. They don't react to stim­u­la­tion from the out­side world. This is ironic, Bar­rett argues, because when sci­en­tists used to believe that limbic regions of the brain were the home of emo­tion, they were seen as mainly reac­tive to the world.

Common sense tells you that seeing is believing, but really the brain is built for things to work the other way around: you see (and hear and smell and taste) what you believe. And believing is largely based on feeling. In her paper, Bar­rett shows that your brain is not wired to be a reac­tive organ. It's wired to ask the ques­tion: "The last time I was in a sit­u­a­tion like this, what sen­sa­tions did I encounter, and how did I act?" And the sen­sa­tions that seem to matter most are the ones that are inside your own body, which are called "interoceptions."

"What your brain is trying to do is guess what the sen­sa­tion means and what's causing the sen­sa­tions so it can figure out what to do about them," Bar­rett said. "Your brain is trying to put together thoughts, feel­ings, and per­cep­tions so they arrive as needed, not a second afterwards."