No abstract

Previous research suggests that infants’ perception of musical rhythm is fine‐tuned to culture‐specific rhythmic structures over the first postnatal year of human life. To date, however, little is known about the neurobiological principles that may underlie this process. In the current study, we used a dynamical systems model featuring neural oscillation and Hebbian plasticity to simulate infants’ perceptual learning of culture‐specific musical rhythms. First, we demonstrate that oscillatory activity in an untrained network reflects the rhythmic structure of either a Western or a Balkan training rhythm in a veridical fashion. Next, during a period of unsupervised learning, we show that the network learns the rhythmic structure of either a Western or a Balkan training rhythm through the self‐organization of network connections. Finally, we demonstrate that the learned connections affect the networks’ response to violations to the metrical structure of native and nonnative rhythms, a pattern of findings that mirrors the behavioral data on infants’ perceptual narrowing to musical rhythms.

Rhythm and meter are fundamental components of music that are universal yet also culture specific. Although simple, isochronous meters are preferred and more readily discriminated than highly complex, nonisochronous meters, moderately complex nonisochronous meters do not pose a problem for listeners who are exposed to them from a young age. The present work uses a behavioral task to examine the ease with which listeners of various ages acquire knowledge of unfamiliar metrical structures from passive exposure. We examined perception of familiar (Western) rhythms with an isochronous meter and unfamiliar (Balkan) rhythms with a nonisochronous meter. We compared discrimination by American children (5 to 11 years) and adults before and after a 2-week period of at-home listening to nonisochronous meter music from Bulgaria. During the first session, listeners of all ages exhibited superior discrimination of isochronous than in nonisochronous melodies. Across sessions, this asymmetry declined for young children but not for older children and adults.

The musical brain is built over time through experience with a multitude of sounds in the auditory environment. However, learning the melodies, timbres, and rhythms unique to the music and language of one’s culture begins already within the mother’s womb during the third trimester of human development. We review evidence that the intrauterine auditory environment plays a key role in shaping later auditory development and musical preferences. We describe evidence that externally and internally generated sounds influence the developing fetus, and argue that such prenatal auditory experience may set the trajectory for the development of the musical mind.

Previous work suggests that auditory–vestibular interactions, which emerge during bodily movement to music, can influence the perception of musical rhythm. In a seminal study on the ontogeny of musical rhythm, Phillips‐Silver and Trainor (2005) found that bouncing infants to an unaccented rhythm influenced infants’ perceptual preferences for accented rhythms that matched the rate of bouncing. In the current study, we ask whether nascent, diffuse coupling between auditory and motor systems is sufficient to bootstrap short‐term Hebbian plasticity in the auditory system and explain infants’ preferences for accented rhythms thought to arise from auditory–vestibular interactions. First, we specify a nonlinear, dynamical system in which two oscillatory neural networks, representing developmentally nascent auditory and motor systems, interact through weak, non‐specific coupling. The auditory network was equipped with short‐term Hebbian plasticity, allowing the auditory network to tune its intrinsic resonant properties. Next, we simulate the effect of vestibular input (e.g., infant bouncing) on infants’ perceptual preferences for accented rhythms. We found that simultaneous auditory–vestibular training shaped the model's response to musical rhythm, enhancing vestibular‐related frequencies in auditory‐network activity. Moreover, simultaneous auditory–vestibular training, relative to auditory‐ or vestibular‐only training, facilitated short‐term auditory plasticity in the model, producing stronger oscillator connections in the auditory network. Finally, when tested on a musical rhythm, models which received simultaneous auditory–vestibular training, but not models that received auditory‐ or vestibular‐only training, resonated strongly at frequencies related to their “bouncing,” a finding qualitatively similar to infants’ preferences for accented rhythms that matched the rate of infant bouncing.