A new study has revealed that people with depression exhibit different brain activity when they observe gestures compared to people without depression. The study, published in Psychiatry Research: Neuroimaging, also found that the type and meaning of the gestures influenced the brain responses.
Gestures are movements of the arms and hands that convey information or emotions. They can be “instrumental” (giving instructions, e.g. pointing) or “expressive” (expressing inner emotions, e.g. clapping). Gestures can also have positive meaning (e.g. thumbs up), or negative meaning (e.g. raised middle finger).
Previous research has illustrated that people with depression, a common mental disorder that affects mood and social functioning, have biases when recognizing and interpreting gestures. However, little is known about how the brain processes gestures in depression, and which particular brain areas are important for this.
“When we communicate with each other, we do not only use words, but also body movements,” said study author Mathilde Sijtsma. “Humans can extract intentions and emotions from body movements, even if the movement is not accompanied by speech, and the movement is only displayed by light points or stick figures. However, prior studies have shown that people with depression experience problems interpreting communicative movements. For instance, they rate them more negatively compared to people without depression.”
“A type of body movement that is especially important for communication is gesture. Gestures can communicate instructions, one’s inner state, or an emotion. The meaning of a gesture is processed by the brain. We were interested in whether there are differences in brain activity between individuals with and without depression while they viewed videos of different types of gestures.”
“Obtaining meaning from gesture is a challenging task for brains to achieve because body form and motion must be dynamically interpreted,” added co-author Frank Pollick, a professor at the University of Glasgow. “We believed it could be a productive area to look for differences in brain mechanisms of depression.”
The research team recruited 12 individuals with depression (aged 33 years old on average) and 12 controls matched for age and biological gender. They employed functional magnetic resonance imaging (fMRI), a technique that measures brain activity by detecting changes in blood flow. The fMRI machine scanned the participants’ brains while they viewed a screen that displayed short animations of stick figures performing different gestures, which were either instrumental or expressive, and either positive or negative.
These stick figures were composed of bright dots located at major joints joined together by lines, which allowed portrayal of human movement while minimizing distracting information such as facial expressions and body shape.
Upon analysis, the researchers found that individuals with depression had overall greater activity in the right claustrum, a brain region involved in integrating sensory, motor (movement), and emotional information, compared to the controls. This suggests that people with depression may require more effort and attention to process the different types of information when they perceive gestures.
“In our study, we found initial support for a difference in brain activity between people with and without depression while they viewed videos of gestures,” Sijtsma told PsyPost. “According to the literature, this difference in brain activity could be related to altered attention in people with depression. It could also be related to a greater effort of those with depression to combine the different types of information that are available while viewing gestures, such as visual, motor and valance information. These hypotheses can be tested in future studies. We hope our study shows that investigating how people with depression perceive gestures, and communicative body movements in general, could help us to better understand this very prevalent mental health disorder.”
Furthermore, viewing instrumental gestures was associated with greater activity in the left cuneus and left superior temporal gyrus, than perceiving expressive gestures. These brain areas are involved in visual processing and motion perception. Sijtsma and colleagues stipulate that this activation may be related to “self-preferential biases” as “instrumental gestures explicitly address an observer, while expressive gestures indicate [someone else’s emotional] state. People process self-relevant [information] in a preferential manner, suggesting that the instrumental gestures captured more attention.”
The researchers also found that perceiving negative gestures was associated with greater activity in the right precuneus and right lingual gyrus than perceiving positive gestures. Both structures have been found to be involved in gesture perception, and the study authors suggested that the increased activity could potentially be explained by a mental bias towards negative situations.
Finally, the researchers found that perceiving negative instrumental gestures was associated with greater activity in various brain regions than perceiving positive instrumental gestures, or expressive gestures (both positive and negative). Specifically, these brain regions were the right precuneus, right lingual gyrus, right paracentral lobule, left cingulate gyrus, right brainstem and left declive, and together these are associated with emotional and social processing, in addition to the perception of biological movement.
“We did not expect that the negative instrumental gestures such as ‘No, you are wrong,’ ‘Do not do that,’ and ‘What time do you call this?’ would provide such a distinctive difference in brain activity. While this didn’t distinguish between depression or not, given the general negativity bias in depression it would be a good place to start future research,” explained Pollick.
The study has some limitations, such as the small sample size, varying medication use among the participants with depression, as well as the use of stick figures instead of full-light displays of gestures, which led to omission of some detail, e.g. hand and finger gestures.
“Our findings are based on the average of a small group of participants and found a single region where activity differed in depression,” Pollick said. “Ultimately, we would want to expand these results to understand how things worked at the level of a single individual with depression.”
“A strength of our study was that we showed our participants different types of gestures, including those communicating an instruction or someone’s feelings, and with a positive or negative meaning,” Sijtsma explained. “However, there are many factors that influence how people perceive gestures. For instance, the speed and size of the hand movements, but also how familiar a person is with a certain gesture. Our study did not explore these factors, but we encourage future studies with more participants to take this direction.”
“Additionally, in our study we used simplified gesture videos, while real-world communication is very complex. For instance, a gesture can be accompanied by speech, and you can see someone’s facial expression. Therefore, future studies could investigate brain activity while people view gestures that are performed live by an actor. This research would complement our findings to create a holistic insight into the differences between the brain activity of people with and without depression.”
The study, “Major Depression and the Perception of Affective Instrumental and Expressive Gestures: An fMRI Investigation”, was authored by Mathilde Sijtsma, Dominic Marjoram, Helen L. Gallagher, Madeleine A. Grealy, David Brennan, Christopher Mathias, Jonathan Cavanagh, and Frank E. Pollick.
