Does your brain know at all what different emotions are?

In ‘How I met your mother’, Stella decides to break up with Ted and to give another opportunity to her ex-husband on the same day they (Stella and Ted) were supposed to get married. When Ted realizes that Stella has moved to her ex-husband’s apartment, he feels enraged. Therefore, he decides to confront Stella and to tell her that she made the biggest mistake in her life. But when he is about to do so, Ted sees Stella walking towards her ex-husband’s apartment; with her ex-husband and their daughter waiting for her at the door. Suddenly, he does not feel angry anymore, because he realizes that they were meant to be a family. So, he decides to let all the anger go and to move forward.

Emotions are powerful components of our day-to-day experience. Emotions guide our actions and emotions change over time. But nevertheless, we are still miles away from an accurate understanding of how emotions are represented in the brain.

Emotions are not represented in single brain areas of the brain. Rather, they are signaled in widespread locations of the brain, including perceptual areas (e.g., occipital cortex), limbic regions (e.g., amygdala) and anterior parts of the brain (e.g., anterior cingulate cortex, orbitofrontal cortex or inferior frontal gyrus) (1–3). So far it seems easy, but things get complicated.

The patterns of brain activity across different emotion categories (e.g., anger, fear or happiness) present huge overlaps. That means, most of the aforementioned areas will be activated in your brain no matter if you are feeling sad, angry or happy (1). And, even more complicated, at a first sight it might even seem as if the brain does not really differentiate between common-sense categories like ‘positive versus negative stimuli’ or ‘appetitive versus aversive stimuli’. Areas like the amygdala, anterior insula or ventral striatum are activated both during positive and during negative stimuli (4,5). Here, though, there are some exceptions. Activity in few specific areas –e.g., the anterior cingulate cortex– seems to predominate in response to appetitive or positive stimuli relative to negative stimuli (4,5). But nevertheless, this seems not to be the case for the majority of brain regions that are considered to play a role in emotional processing.

So, is the brain blind to the emotional experience? How can it be the same to feel love than to feel disgust or to feel sad than to feel happy? Even more important and transcendental: should we start creating a whole new vocabulary with words like ‘lovegust’ or ‘sadppy’ in order to refer to emotionally overlapping scenarios? Well… I’m afraid it might not be necessary…

At the beginning of this month, an exciting new study was published. The authors were able to demonstrate that each emotion category was associated with separable patterns of brain activity across multiple brain systems (6). In other words, what it might differentiate between different emotions is not the single areas that activate in response to a certain stimuli, but rather, which networks co-activate together in order to represent that emotional category in the brain (6).

The profiles obtained for each emotion are insightful, and help to understand biological mechanisms behind the emotional experience. To put a few examples of this, anger and fear recruited areas ascribed to the cortical dorsal attentional network. This fact was interpreted as reflecting an engagement of neural processes supporting orientation towards external stimuli. Contrarily, disgust was characterized by coactivity in basal ganglia and somatomotor areas. The authors proposed that this pattern might support an orientation towards internal perceptions (6).

Lots of questions in emotion research remain unanswered. How does the brain ‘move’ from one emotion to the other? Which is the influence of ‘cognitive’ processes during the perception of emotional experience? Nevertheless, the study points to the direction of the importance of focusing on patterns of co-activation in the study of the neural representation of emotions.

 

REFERENCES

  1. Lindquist KA, Wager TD, Kober H, Bliss-Moreau E, Barrett LF. The brain basis of emotion: a meta-analytic review. Behav Brain Sci. 2012; 35(3):121–43.
  2. Carretié L, Albert J, López-Martín S, Tapia M. Negative brain: an integrative review on the neural processes activated by unpleasant stimuli. Int J Psychophysiol. 2009; 71(1):57–63.
  3. Fusar-Poli P, Placentino A, Carletti F, Landi P, Allen P, Surguladze S, et al. Functional atlas of emotional faces processing: a voxel-based meta-analysis of 105 functional magnetic resonance imaging studies. J Psychiatry Neurosci. 2009; 34(6):418–32.
  4. Lindquist KA, Satpute AB, Wager TD, Weber J, Barrett LF. The Brain Basis of Positive and Negative Affect: Evidence from a Meta-Analysis of the Human Neuroimaging Literature. Cereb Cortex. 2015;1–13.
  5. Hayes DJ, Duncan NW, Xu J, Northoff G. A comparison of neural responses to appetitive and aversive stimuli in humans and other mammals. Neurosci Biobehav Rev. 2014;45C:350–68.
  6. Wager TD, Kang J, Johnson TD, Nichols TE, Satpute AB, Barrett LF. A Bayesian Model of Category-Specific Emotional Brain Responses. PLOS Comput Biol. 2015;11(4):e1004066.
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