Morgan L. Gustison

Rhythmic patterning is a widespread structural trait of animal (including human) communication. Concomitantly, a key role of communication functions to convey and induce emotion. The expression and modulation of emotion is also hypothesised to be a key mechanism underlying the evolution of rhythmic synchronisation in humans. Despite the centrality of both rhythm and emotion to human and nonhuman communication, a systematic treatment of the link between them is currently lacking. In this chapter, we bridge these two areas of research by reviewing findings from human and animal studies. These studies how rhythmic properties encode and communicate emotional states and how variations in these properties influence the emotional states of receivers. Taken together, this review of literature demonstrates that the main rhythmic parameter currently evaluated in emotion research is temporal rate (often referred to as frequency rate), which is reliably associated with levels of emotional arousal in all surveyed taxa. We discuss a range of neurobiological mechanisms that could link rhythm and emotion. We also identify several avenues for future research that address current limitations, such as the overwhelming focus on the acoustic modality and frequency rate, while other communication modalities and rhythmic feature remain understudied.

In this concluding chapter, we focus on outlining the next frontier in research on rhythm cognition and rhythmic communication (RCC), synthesising conceptual, methodological, comparative, and applied directions, as they emerge from the contributions to the Nature Beats volume . While consensus has grown regarding the composite nature of rhythmic competence and the need for integrated quantitative approaches, the field remains marked by conceptual heterogeneity and inconsistent operational criteria. To advance RCC research, the chapter identifies pressing needs for conceptual clarity, methodological standardisation, and ecologically grounded definitions of rhythmic phenomena across modalities and species. We also highlight future research trajectories for major theoretical frameworks, including the Vocal Learning–Beat Perception and Synchronisation hypothesis, Gradual Audiomotor Evolution hypothesis, Neural Resonance Theory, socio-ecological hypotheses of synchrony, and evolutionary accounts linking rhythm to social bonding and stress regulation. A bottom-up, species-specific, and comparative approach is advocated to capture the full structural and functional diversity of RCC and to evaluate mechanisms spanning neural oscillations and functional connectivity, biomechanics, development, reward systems, and environmental constraints. Finally, the chapter emphasises the translational value of RCC research. Rhythm-based interventions hold promise for educational, clinical, welfare, conservation, and human-animal interaction contexts. By integrating mechanistic, evolutionary, and applied perspectives, future research can uncover the biological principles underlying rhythmic behaviour and its central role in communication, cognition, and sociality across the animal kingdom.

Vocal communication is widespread across animals, from mammals to amphibians. In recent years, rodents have become an increasingly valuable group in which to study vocal communication. Rodents offer rich opportunities to examine vocalizations from proximate and ultimate ethological perspectives. Here, we identify recent advances in ethological research on rodent vocal communication by synthesizing contemporary studies from the past decade. We carried out a scoping review of research published between 2014 and 2024. This review involved a broad search for peer-reviewed primary research studies in APA PsycINFO, Embase, MEDLINE, PubMed, Scopus, and Web of Science databases. The search yielded 403 eligible studies on rodent vocalizations. We extracted information about the ethological perspectives, species, research environment, and animal sex and age groups. We also identified studies that focused on method development. We found that rodent vocal communication studies varied across ethological perspectives, with more studies carried out on vocal mechanisms and adaptive functions than on development and evolution. These studies covered a broad range of 88 rodent species, with high species diversity in function and evolution studies and low species diversity in mechanism studies. Artificial environments were used more often than naturalistic environments, especially in mechanism and development studies. Naturalistic environments were common in function and evolution studies. Adult males were used more often than any other sex and age groups. The use of age groups, but not sexes, varied across ethological perspectives. Together, these findings highlight several advantages of contemporary rodent research, including opportunities to carry out in-depth studies of vocal mechanisms and to compare diverse species. Based on these findings, we also identify potential areas for future research. These research areas include non-mechanistic questions, as well as expanding species diversity, research environments, and animal sex and age groups. Rodent research from multiple ethological perspectives will be crucial for building a comprehensive understanding of animal acoustic communication.

Neurodevelopmental disorders (NDDs) have dramatically increased in prevalence to an alarming one in six children, and yet both causes and preventions remain elusive. Recent human epidemiology and animal studies have implicated developmental exposure to pyrethroid pesticides, one of the most common classes of pesticides in the US, as an environmental risk factor for autism and neurodevelopmental disorders. Our previous research has shown that low-dose chronic developmental pyrethroid exposure (DPE) changes folate metabolites in the adult mouse brain. We hypothesize that DPE acts directly on molecular targets in the folate metabolism pathway, and that high-dose maternal folate supplementation can prevent or reduce the biobehavioral effects of DPE. We exposed pregnant prairie vole dams chronically to vehicle or low-dose deltamethrin (3 mg/kg/3 days) with or without high-dose folate supplementation (methylfolate, 5 mg/kg/3 days). The resulting DPE offspring showed broad deficits in five behavioral domains relevant to neurodevelopmental disorders (including the social domain); increased plasma folate concentrations; and increased neural expression of SHMT1, a folate cycle enzyme. Maternal folate supplementation prevented most of the behavioral phenotypes (except for repetitive behaviors) and caused potentially compensatory changes in neural expression of FOLR1 and MTHFR, two folate-related proteins. We conclude that DPE causes neurodevelopmental disorder-relevant behavioral deficits; DPE directly alters aspects of folate metabolism; and preventative interventions targeting folate metabolism are effective in reducing, but not eliminating, the behavioral effects of DPE.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area, and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward, and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.