The def­i­n­i­tion of emo­tion has intrigued philoso­phers, physi­cians and psy­chol­o­gists for cen­turies. Is it a basic bio­logic state or does it emerge from other phys­i­o­log­ical components?

Lisa Feldman Bar­rett, Dis­tin­guished Pro­fessor of Psy­chology in the Col­lege of Sci­ence, ana­lyzed 20 years’ worth of neu­roimaging studies to find out.

The results, which will be pub­lished in June in the journal Behav­ioral and Brain Sci­ences, chal­lenge con­ven­tional wisdom.

Right now, the field and even pop­ular cul­ture writes about the brain as if spe­cific psy­cho­log­ical events are local­ized to spe­cific brain tis­sues,” Bar­rett said. “So, for example, when you have a memory it hap­pens in the hip­pocampus and when you have fear it hap­pens in the amygdala.”

Barrett’s find­ings sug­gested the exact opposite.

Her Inter­dis­ci­pli­nary Affec­tive Sci­ence Lab­o­ra­tory com­pleted a meta-​​analysis of thou­sands of data points from hun­dreds of studies between the years 1990 and 2005. The find­ings sug­gest that brain regions once thought to be specif­i­cally and con­sis­tently asso­ci­ated with par­tic­ular emo­tions are in fact active across a variety of emo­tional — and even non-​​emotional — states.

Neu­roimaging studies don’t directly mea­sure neural activity, Bar­rett explained. Instead, they mea­sure blood-​​flow changes in the brain. These changes, when ampli­fied, can be mea­sured as fluc­tu­a­tions in a larger mag­netic field.

So then you’ve got to figure out what’s signal and what’s noise,” Bar­rett said. “Which changes are telling you about neu­rons firing in the brain and which ones are not.”

There are two ways to tease out the real data from the noise — either repeat the study hun­dreds of times or limit the sta­tis­tical analysis to “only look at the points of activity in the brain that are the most intense,” Bar­rett said.

Most neu­roimaging studies, which assume that emo­tion is local­ized to spe­cific brain regions such as the amyg­dala or the insula, choose the latter approach, since the former is nearly impos­sible in terms of time and cost.

To avoid these lim­i­ta­tions, Bar­rett and her team ana­lyzed the entire body of lit­er­a­ture. They found that emo­tions, sur­pris­ingly, are not specif­i­cally asso­ci­ated with par­tic­ular brain regions. Some brain regions were con­sis­tently acti­vated across emo­tions and tended to be active in studies of other mental states such as memory or attention.

These data sug­gest that the brain is pop­u­lated by a set of basic oper­a­tions, or ingre­di­ents, that are not spe­cific to emo­tions or thoughts or mem­o­ries,” Bar­rett said.

The idea is that thoughts, mem­o­ries and emo­tions are sub­jec­tive dis­tinc­tions that we make,” she added. “Other cul­tures don’t make the dis­tinc­tion between cog­ni­tion and emotion.”

The amyg­dala, for example, which Bar­rett said is one of the most con­nected regions in the brain, doesn’t fire only when a person expe­ri­ences fear, but when­ever the brain doesn’t have enough infor­ma­tion about what to do next. Some­times, but not always, we sub­jec­tively expe­ri­ence this uncer­tainty as fear, Bar­rett said.

In the six years between 2005 and 2011, more than 200 addi­tional neu­roimaging studies have emerged. Barrett’s team has added these to the data­base and will begin looking for rep­re­sen­ta­tive pat­terns across the brain. This might allow researchers to pre­dict emo­tional states, which could have far reaching impli­ca­tions for future psy­cho­log­ical studies.