Research uncovers surprising neural hubs in the brain driving marmoset communication
Marmosets rely heavily on acoustic communication to build and maintain social connections. “Much of what we know about this comes from studies conducted in artificial task settings, such as marmosets interacting with virtual counterparts generated by computers. These set-ups may not fully capture how the brain operates under natural conditions,” notes Arthur Lefevre, coordinator of MarmOT, a project funded by the Marie Skłodowska-Curie Actions programme. The research focused on the brains of spontaneously behaving animals. By observing these primates’ neural activity in their natural settings, the researcher gained a clearer picture of how their brains function in everyday situations. “Specifically, we explored the ‘cocktail party effect’. This phenomenon referring to an individual’s ability to maintain conversations within crowded and noisy environments – a task showcasing the sophisticated nature of communication,” adds Lefevre.
Popular yet highly intriguing primates
For his study, the researcher focused on common marmosets(opens in new window), highly sociable primates with several characteristics that render them ideal for studying both the biology and the social dynamics of communication. “These primates possess a rich repertoire of calls, enabling them to identify each other without seeing them. They also exhibit rare traits such as vocal turn-taking(opens in new window) and vocal learning, which are uncommon even among other primates,” explains Lefevre. Furthermore, marmosets form pair bonds and participate in cooperative care of their newborns – traits that emphasise their pro-social behaviour.
New wireless brain recording techniques
The researcher started his research by mapping oxytocin fibres in the marmoset brain and discovered them in the anterior cingulate cortex (ACC). Since oxytocin modulates social behaviour and the ACC affects communication, he hypothesised that oxytocin could modulate vocal communication. To test this, he began developing adeno-associated viruses (AAV) that target oxytocin neurons and activate them on demand. However, this process took longer than expected and was only completed during the project’s end phase, so it could not be used in the experiments. Experiments are now underway in the researcher’s laboratory(opens in new window). On the more technical side, the researcher focused on improving wireless electrophysiology(opens in new window). “I developed new methods to record more neurons simultaneously. This was a key step for the project as it allowed me to not just study a few neurons per session but to record hundreds,” highlights Lefevre. The researcher also successfully implanted multiple micro wire brush arrays or neuropixel probes in the same animal, which had never been used wirelessly before.
New clues to how marmosets understand, share and filter sounds
“We made several new discoveries about Area 24(opens in new window) in the brain. While it was already known to be involved in vocalisation production, we found it also affects vocalisation perception. By analysing neural activity, we could decode what type of calls marmosets made or heard,” states Lefevre. The researcher also discovered that this particular brain area provides information about whether a marmoset engages in an interaction. “For example, we could tell from brain activity if the marmoset’s vocalisations were isolated or part of an active exchange, as marmosets take turns when communicating.” “Ultimately, we found that the ACC processes calls in a way that ignores other overlapping sounds, showing it handles auditory information in a way akin to the cocktail party effect. This highlights the ACC’s central role in communication, even though it was not hitherto seen as part of the language network,” concludes Lefevre.
Keywords
MarmOT, marmosets, acoustic communication, vocalisation, language network, primate calls, neural activity, cocktail party effect, vocal turn-taking, anterior cingulate cortex, ACC
