This 2015 analysis of emotion studies found:
“Emotion categories [fear, anger, disgust, sadness, and happiness] are not contained within any one region or system, but are represented as configurations across multiple brain networks.
For example, among other systems, information diagnostic of emotion category was found in both large, multi-functional cortical networks and in the thalamus, a small region composed of functionally dedicated sub-nuclei.
The dataset consists of activation foci from 397 fMRI and PET [positron emission tomography] studies of emotion published between 1990 and 2011.”
From the fascinating Limitations section:
“Our analyses reflect the composition of the studies available in the literature, and are subject to testing and reporting biases on the part of authors. This is particularly true for the amygdala (e.g., the activation intensity for negative emotions may be over-represented in the amygdala given the theoretical focus on fear and related negative states). Other interesting distinctions were encoded in the thalamus and cerebellum, which have not received the theoretical attention that the amygdala has and are likely to be bias-free.
Some regions—particularly the brainstem—are likely to be much more important for understanding and diagnosing emotion than is apparent in our findings, because neuroimaging methods are only now beginning to focus on the brainstem with sufficient spatial resolution and artifact-suppression techniques.
We should not be too quick to dismiss findings in ‘sensory processing’ areas, etc., as methodological artifacts. Emotional responses may be inherently linked to changes in sensory and motor cortical processes that contribute to the emotional response.
The results we present here provide a co-activation based view of emotion representation. Much of the information processing in the brain that creates co-activation may not relate to direct neural connectivity at all, but rather to diffuse modulatory actions (e.g., dopamine and neuropeptide release, much of which is extrasynaptic and results in volume transmission). Thus, the present results do not imply direct neural connectivity, and may be related to diffuse neuromodulatory actions as well as direct neural communication.”
Why did the researchers use only 397 fMRI and PET studies? Why weren’t there tens or hundreds of times more candidate studies from which to select?
The relative paucity of candidate emotion studies demonstrated the prevalence of other researchers’ biases for cortical brain areas. The lead researcher of the current study was a coauthor of the 2016 Empathy, value, pain, control: Psychological functions of the human striatum, whose researchers mentioned that even their analyses of 5,809 human imaging studies was hampered by other imaging-studies researchers’ cortical biases.
Functional MRI signals depend on the changes in blood flow that follow changes in brain activity. Study designers intentionally limit their findings when they scan brain areas and circuits that are possibly activated by human emotions, yet exclude emotional content that may activate these areas and circuits.
Here are a few examples of limited designs that led to limited findings when there was the potential for so much more:
- A missed opportunity to study image-evoked emotional memories
- Emotionless brain research that didn’t deal with human reality
- A missed opportunity to study odor-evoked emotional memories
It’s well past time to change these practices now that we’re in 2016.
This study provided many methodological tests that should be helpful for research that includes emotion. It showed that there aren’t impenetrable barriers – other than popular memes, beliefs, and ingrained dogmas – to including emotional content in studies.
Including emotional content may often be appropriate and informative, with the resultant findings advancing science. Here are a few recent studies that did so:
- Do strong emotions cause our brain hemispheres to interact more closely?
- The emotional power of environmental sounds affects our sensory experiences
- The cerebellum’s role in human behavior and emotions
http://journals.plos.org/ploscompbiol/article?id=10.1371%2Fjournal.pcbi.1004066 “A Bayesian Model of Category-Specific Emotional Brain Responses”