Sensory-Motor Brain Networks are Coupled with the Stomach’s Rhythm
Post by Leanna Kalinowski
The takeaway
Natural electrical rhythms produced in the stomach are coupled with resting-state activity in sensory and motor brain regions, providing insights into how the brain and body communicate.
What's the science?
The study of resting state brain networks (RSNs) – areas of the brain that work synchronously even during times of rest – has taught neuroscientists a lot about how brain activity is organized across distinct brain regions. Traditionally, these networks have been broadly categorized into groups of sensory-motor regions, which allow for interaction with the external environment, and groups of transmodal regions, which control cognitive processing. However, despite a growing interest in how the brain and body interact, little work has been done to identify potential relationships between RSNs and internal bodily rhythms outside of the brain.
Scientists have previously identified a connection between brain activity at rest and the gastric rhythm, which is a slow electrical rhythm that is continuously produced in the stomach. This week in the Journal of Neuroscience, Rebollo and Tallon-Baudry further characterized the connections between this gastric rhythm and RSNs.
How did they do it?
To measure brain activity at rest, 72 participants underwent functional magnetic resonance imaging (fMRI) scans while resting; they were instructed to lay still and fixate on a bull’s eye on a grey screen. To measure gastric rhythm, the participants simultaneously underwent electrogastrogram (EGG) recordings in which non-invasive electrodes were placed over their abdomen. The researchers then filtered the fMRI signals to match the slow electrical rhythm of the stomach; a technique called phase synchronization. This way, they were able to measure how stable the lag between the two signals was over time.
What did they find?
The researchers found that rhythms in all sensory and motor cortices are coupled with the gastric rhythm, including brain regions that respond to touch, vision, audition, and interoception. In contrast, very few brain regions associated with cognitive processing (i.e., transmodal RSNs) are coupled with the gastric rhythm. Taken together, these results suggest that gastric rhythm and sensory-motor processes likely interact while bypassing cognitive processes.
What's the impact?
The results from this study transform what we previously knew about how brain activity is organized. Notably, fluctuations in the activity of brain regions that have been largely considered to be independent are in fact coupled with gastric activity. Future research should be conducted to further characterize connections between the brain and body.