Neural Networks for Beat Perception in Musical Rhythm

Abstract

Entrainment of cortical rhythms to acoustic rhythms has been hypothesized to be the neural correlate of pulse and meter perception in music. Dynamic attending theory first proposed synchronization of endogenous perceptual rhythms nearly 40 years ago, but only recently has the pivotal role of neural synchrony been demonstrated. Significant progress has since been made in understanding the role of neural oscillations and the neural structures that support synchronized responses to musical rhythm. Synchronized neural activity has been observed in auditory and motor networks, and has been linked with attentional allocation and movement coordination. Here we describe a neurodynamic model that shows how self-organization of oscillations in interacting sensory and motor networks could be responsible for the formation of the pulse percept in complex rhythms. In a pulse synchronization study, we test the model's key prediction that pulse can be perceived at a frequency for which no spectral energy is present in the amplitude envelope of the acoustic rhythm. The result shows that participants perceive the pulse at the theoretically predicted frequency. This model is one of the few consistent with neurophysiological evidence on the role of neural oscillation, and it explains a phenomenon that other computational models fail to explain. Because it is based on a canonical model, the predictions hold for an entire family of dynamical systems, not only a specific one. Thus, this model provides a theoretical link between oscillatory neurodynamics and the induction of pulse and meter in musical rhythm.

Neural Entrainment to the Beat: The “Missing-Pulse” Phenomenon

“…The current results are in line with theoretical predictions of NRT (Large and Snyder, 2009) associating pulse perception with emergence of neural phase locking at the pulse frequency. NRT predicts that, due to higher-order resonances, when neural oscillators are driven by an acoustic stimulus, oscillations may emerge at favored frequency ratios (harmonics, subharmonics, and integer ratios), not always present in a linear frequency analysis of the acoustics (Velasco and Large, 2011).…”

“…Moreover, the neural response to stimulus MP1 exhibited a peak at 1 Hz, in addition to the 2 Hz peak. It is well established that pulse perception is dynamic and flexible, and the perceived pulse frequency for a given stimulus can vary across and even within individuals (for review, see Repp and Su, 2013), and can be intentionally changed (Large et al, 2002;Nozaradan et al, 2011). Thus, another prediction to be tested in future studies is whether the dominant missing-pulse frequency in the neural signal reflects the specific pulse frequency induced in a given trial.…”

“…Moreover, an almost automatic response is to move to the beat of the music (Nettl, 2000;Michaelis et al, 2014). The process through which a percept of pulse emerges is referred to as induction, and most listeners are quite accurate in identifying and tapping to a pulse, even for highly nonisochronous rhythms (Large et al, 2002Patel et al, 2005).…”

“…Large and colleagues recently proposed a computational model, neural resonance theory (NRT), for explaining how nonperiodic stimuli interact with endogenous brain rhythms to induce the percept of a periodic pulse (Snyder and Large, 2005;Large, 2008;Large and Snyder, 2009). According to NRT, the pulse emerges through nonlinear coupling between two oscillatory networks-one representing the physical properties of the stimulus (labeled "sensory"), and a second (labeled "motor") that integrates inputs from the sensory system.…”

“…We were also interested in testing whether the emergence of a neural representation for the pulse was linked to the behavioral perception of a pulse, since previous studies have suggested that pulse induction for syncopated rhythms is not "automatic," but requires attention (Chapin et al, 2010) and can be modified by instruction (Large et al, 2002;Nozaradan et al, 2011).…”