A new study maps complex affective states to within an area of the brain just 3 centimeters (cm) in size.
An innovative new study has unveiled a small, 3 cm area in the brain where emotions are registered.
The study examined the correlation between data from two experiments measuring participant responses to the same movie.
The first experiment gathered self-reported emotional responses to each scene in the movie.
The second gathered data from a brain imaging study that measured activated regions within the cortices of participants while they watched the movie.
Researchers from the Molecular Mind Laboratory (MoMiLab) at the IMT School for Advanced Studies Lucca, Italy, worked on the new study.
They combined the functional MRI (fMRI) data — collected during a study conducted at Otto von Guericke University Magdeburg in Germany — with data from a behavioral study they conducted at the MoMiLab at IMT.
The ultimate aim of their study, which now appears in the journal Nature, was to map and locate cortical regions where emotions are encoded. Doctoral candidates Giada Lettieri and Giacomo Handjaras led these research efforts.
Acting out emotions we see on screen
In order to evoke an array of emotions from the participants in the study, the team at MoMiLab showed them a movie popular for its emotional storyline.
The study authors explain that witnessing the emotions of others, even those of actors, can cause us to react with the same or similar emotions. They say:
“To understand our own emotions, as well as those of others, is crucial for human social interactions. Also, witnessing facts and events of others’ life sometimes prompts inner reactions related to the beliefs, intentions, and desires of actors.”
Matching emotions with brain activity
For the study, the researchers collected scene-by-scene emotional reactions that the participants had during the movie.
They asked the participants to rate their responses to each scene from six basic emotions: happiness, surprise, fear, sadness, anger, and disgust.
The participants also recorded how strong the feeling was, with a number ranging between 1 and 100.
The team used open science data available from a German study called “study forrest,” which provided brain imaging data from the fMRI scans of 15 participants showing which regions were active during each scene of the same movie.
Finally, the team analyzed the data from both studies, comparing the self-reported measures of emotion against the fMRI data.
Mapping emotions encoded in the brain
Lettieri and team were able to create a topographical map by plotting the emotions of the participants who rated their responses to the movie against the brain imaging data from the participants in Germany.
The map plots the arrangement of neural receptors within the body — which sense physiological sensations of emotion — with the distribution of neurons that represent the same functions within the cortical sensory regions of the brain.
This provided a picture of where certain bodily sensations are encoded in the brain.
Lettieri and Handjaras named this approach “emotionotopy,” in connection with the similar technique of retinotopy. This refers to the mapping of how visual data is represented within the brain.
Three gradients of emotion
By matching up the behavioral ratings with the fMRI scans, the team at IMT revealed that emotions were encoded within three independent but overlapping gradients:
- Polarity. This refers to the opposing measures of positive or negative feeling states.
- Complexity. This refers to the amount of variance between emotions when they combine.
- Intensity. This refers, for example, to the arousal level of each experienced emotion.
The team mapped these emotional experiences within a specific area of the brain: the right temporoparietal cortex.
Armed with the data from the specific moments an emotion was triggered, the researchers were able to unveil the spatial arrangements of specific emotions, as well as the perceived intensities of those emotions within the brain.
Connecting feeling states to biology
This study demonstrates how making use of open science data can free up resources and energy to tread new ground.
The team was able to focus its efforts on constructing a unique approach for identifying and locating where emotions are encoded in the brain without conducting its own fMRI study.
The study also provides more of an understanding about how psychiatry and biology combine within the body.
Also, these findings have real-world implications for people with mental health issues, notes study co-author Pietro Pietrini.
“Dissecting the brain correlates of elementary factors that modulate intensity and quality of our emotions has major implications to understand what happens when emotions [become pathological], as in [the] case of depression and phobia,” says Pietrini.
“These studies are getting psychiatry closer to other fields of medicine in finding objective biological correlates of feelings, which are subjective states.”
– Pietro Pietrini
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