Research

How Regions of the Brain Eavesdrop on Each Other

Auditive Cognition: Regions of our brain intercommunicate and thereby impact our hearing ability

The ability to listen to another person, while blocking out other disturbing noises and voices, depends on how well regions of your brain are structured to intercommunicate and pay attention to that person. At our Universität zu Lübeck, an interdisciplinary research group comprising a biomedical engineer, a linguist and a psychologist was able to demonstrate that speech comprehension in our daily routine depends on finely-tuned reconfiguration of brain networks. Imagine that you are sitting in a restaurant full of customers, trying to listen to what your companion at the opposite end of the table is saying, surrounded by a variety of distracting sounds. Now, though all of us hear sounds primarily through our ears, the ability to focus on a particular speaker hinges on interactions among various parts of our human brain. People differ in how well they can focus on one speaker in difficult auditory circumstances. Researchers at our Universität zu Lübeck have been able to show that such differences among individuals depend on how well spatially separated regions of our brain adapt to such communications. Communication in our brain is governed by how different networks interact, whereby examples of common forms of networks are flight connections between different airports, or links among friends in social networks. All these networks contain numerous unique nodes – equivalent to different parts of a brain in our case – that are interconnected. Another key property of networks is the bundling of nodes and connections in small units or modules. The stronger the degree of such modularity in a network, the more one can subdivide the entire network into groups of interlinked nodes. The structuring of brain networks allows coordinated and targeted flows of information in the brain. Our Lübeck scientists in the Auditive Cognition group investigated whether the extent to which our brain regions intercommunicate is the determinant for how well we can hear. Dr Mohsen Alavash, co-leader of this study, explains, “We assumed that for adapting to difficult listening situations, it would also be necessary to modify communications between parts of the brain. Hence, we especially delved into subdividing the big networks into small modules. We expected that the configuration among these network modules, and thereby their intercommunications, would change when adapting to difficult listening tasks.” For this purpose, the researchers used an MRI to scan brain activity of test subjects as they either lay still in the scanner or were supposed to focus on one of two simultaneous voices heard through headphones. Not surprisingly, some subjects were better able to repeat the words of the targeted speaker. Can one explain the observed differences in one’s ability to follow the speech of a particular speaker through differences in how brain networks communicate? “We were able to demonstrate changes in the grouping of modules when the subjects shifted from staying still to the demanding task of listening,” says Dr Sarah Tune, a co-leader of the study. Prof. Dr Jonas Obleser, Head of the Auditive Cognition Research Group adds, "Persons in whom we observed greater reconfiguration of brain modules – which we interpret as better neural adaption to the task – actually performed their listening task better.” The scientists were able to show that during the task of focussing, not only known regions of the brain were involved, but also regions associated with paying attention. The researchers now hope to better understand such reconfiguration of brain networks and the resulting differences in hearing, to help drive future advances in treating speech recognition problems and development of better hearing aids. Original publication
Alavash M, Tune S, Obleser J (2018) Modular reconfiguration of an auditory-control brain network supports adaptive listening behavior. Proc Natl Acad Sci USA, online 26. December 2018. DOI: doi.org/10.1073/pnas.1815321116