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.
To address this gap, the research team led by Mathilde Sijtsma from the University of Glasgow recruited 12 individuals with depression (aged 33 years old on average) and 12 controls matched for age and biological gender.
Sijtsma and colleagues 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.
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.
The study team explained this phenomenon, “for the [depressed] group these regions would activate particularly for negative instrumental gestures such as ‘No, you are wrong’, ‘Do not do that’, ‘What time do you call this?’ where there is the potential for an observer to subjectively feel scolded by the stick-figure animation. Such a subjective interpretation is not readily available for either the positive or negative expressive gestures or the positive instrumental gestures.”
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.
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.
