Neural mechanisms underlying rapid changes of vocal behavior in marmoset monkeys.

• Applicant: Julia Löschner
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540572644

Vocal signals have evolved as the primary means of direct communication among individuals in many species of birds and mammals including humans. However, vocal communication frequently occurs in environments with competing sound sources. To enable effective communication, the sender must be able to adjust the signal's temporal and spectral characteristics to overcome ambient noise interference and ensure successful signal transmission. The mechanisms used to handle acoustic disturbances can be categorized into two primary types. First, animals and humans show adaptive vocal behaviors in response to elevated ambient noise levels. Here, one prevalent strategy is the Lombard effect, wherein call amplitude involuntarily increases in response to masking noise enhancing the signal-to-noise ratio, to makes the sent message more detectable. Second, vocalizations can be ceased when there is high acoustic disruption and resumed when perturbing noise subsides. Such a synchronization of vocal output with periods of lower noise levels, enhances the comprehensibility and efficiency of vocal communication signals. In our recent work, we found that marmoset monkeys, a highly vocal New World Monkey species, are able to interrupt ongoing phee calls after noise perturbation onset. However, it is yet unclear, how and on which brain level the vocal motor network is affected by such auditory perturbations. Here, recent work point to the auditory and insular cortices, which have been identified as critical hubs in audio-vocal integration, by being involved in both vocal processing and call production.In this project, I aim to investigate the role of the insular cortex and higher-order auditory cortical areas in mediating the observed rapid flexibility of vocal motor control in response to perturbing noise in marmosets. I will record the activity of single neurons in vocalizing monkeys and study how canceling of marmoset calls is encoded. To explain potential differences, I will conduct this approach in two different work programs. In WP1 I will investigate the neural activity underlying vocal responses to noise perturbation in a well-established, highly controlled approach. This setup allows to limit the degrees of freedom within the monkeys’ behavior and correlate the recorded neural activity with cognitively controlled vocal behavior. In WP2, I will record vocalization-correlated neural activity in freely moving monkeys to investigate differences in vocal behavior with and without noise perturbation in a complex environment. By conducting both experiments, it will be possible to investigate whether and in which way vocal motor control mechanisms differ between different behavioral conditions, and if yes, to study the underlying principles. The multidisciplinary approach of this project merges behavioral observations, neural recordings, and acoustic analysis to progress our understanding of the underlying neural basis of vocal adaptation in marmoset monkeys.

• DFG Programme: WBP Position