Extracting the Beat: An Experience-dependent Complex Integration of Multisensory Information Involving Multiple Levels of the Nervous System

Abstract

In a series of studies we have shown that movement (or vestibular stimulation) that is synchronized to every second or every third beat of a metrically ambiguous rhythm pattern biases people to perceive the meter as a march or as a waltz, respectively. Riggle (this volume) claims that we postulate an "innate", "specialized brain unit" for beat perception that is "directly" influenced by vestibular input. In fact, to the contrary, we argue that experience likely plays a large role in the development of rhythmic auditory-movement interactions, and that rhythmic processing in the brain is widely distributed and includes subcortical and cortical areas involved in sound processing and movement. Further, we argue that vestibular and auditory information are integrated at various subcortical and cortical levels along with input from other sensory modalities, and it is not clear which levels are most important for rhythm processing or, indeed, what a "direct" influence of vestibular input would mean. Finally, we argue that vestibular input to sound location mechanisms may be involved, but likely cannot explain the influence of vestibular input on the perception of auditory rhythm. This remains an empirical question for future research. KEYWORDS: rhythm, meter, vestibular, experience-dependent, multisensory, sound location IN his paper "A simpler explanation for vestibular influence on beat perception: No specialized unit needed", Riggle (this volume) misinterprets our papers (Phillips-Silver & Trainor, 2005, 2007Trainor et al., 2009) on movement-auditory interactions, and then presents evidence that he claims contradicts our findings. However, nothing in his paper actually argues against any of our findings. Because questions related to the mechanisms of auditory-vestibular interaction -and their phylogenetic and ontogenetic origins -are of fundamental importance in understanding both auditory perception and musical behaviour, in this reply we will engage in a constructive discussion of the critical question concerning whether auditory-vestibular interactions for rhythm are explained by auditory-vestibular interactions for locating sounds in space. But first it is necessary to set the record straight with respect to our experimental findings and our interpretation of the results.In the series of studies cited above, we have shown that when played a metrically ambiguous auditory rhythm (i.e., one with no physical accents), both adults and infants can be biased to perceive it as a march (with perceived accents every second beat) or as a waltz (with perceived accents every third beat) by engaging them in rhythmic movement synchronized to every second or every third beat of the ambiguous auditory rhythm, respectively. Furthermore, we have shown that stimulation of the vestibular nerve in such a way as to give rise to the sensation of head movement synchronized to every second or to every third beat of the metrically ambiguous rhythm (in the absence of actual movement) also biases metrical interpretation for a marc...

Neural tracking of the musical beat is enhanced by low-frequency sounds

“…Instead, the low-tone benefit observed here could be explained by a greater recruitment of brain structures involved in movement planning and control, including motor cortical regions ( 37 – 42 ), the cerebellum, and basal ganglia ( 24 ). These structures may be recruited via functional interconnections between the ascending auditory pathway and a vestibular sensory-motor network (including a striatal circuit involved in beat-based processing) that is particularly responsive to bass acoustic frequencies ( 43 – 45 ). The involvement of these sensory-motor areas thus constitutes a plausible mechanism for the observed low-tone benefit, as these areas have been shown to be critically involved in predictive beat perception ( 42 ), to contribute to the selective enhancement of EEG responses at the beat frequency ( 24 ), and to be activated by vestibular input ( 43 , 44 ).…”

“…It should be noted that direct activation of the human vestibular organ by bass sounds occurs only at higher intensities (above ∼95-dB sound pressure level) than those employed in the current study ( 46 ). However, functional interactions between auditory and vestibular sensory-motor networks in response to low-frequency rhythms can arise centrally ( 45 ). These neural connections presumably develop from the onset of hearing in the fetus through the continuous experience of correlated auditory and vestibular sensory-motor input (e.g., the sound of the mother’s footsteps coupled with walking motion) ( 45 ).…”

“…However, functional interactions between auditory and vestibular sensory-motor networks in response to low-frequency rhythms can arise centrally ( 45 ). These neural connections presumably develop from the onset of hearing in the fetus through the continuous experience of correlated auditory and vestibular sensory-motor input (e.g., the sound of the mother’s footsteps coupled with walking motion) ( 45 ).…”

The sensory-motor theory of rhythm and beat induction 20 years on: a new synthesis and future perspectives

“…More critically it was demonstrated that head movement and therefore activation of the vestibular apparatus was necessary to observe the effect (Phillips-Silver and Trainor, 2007 ), and further that vestibular influence could be achieved directly by using galvanic vestibular stimulation (Trainor et al, 2009 ). However, the matter remains controversial, with some authors suggesting that the vestibular influence is not direct (Trainor, 2007 ; Riggle, 2009 ; Trainor and Unrau, 2009 ).…”

Do metrical accents create illusory phenomenal accents?

“…The plausibility of this interpretation is enhanced by a recent demonstration that not only actual movement involving the head but also rhythmic electrical stimulation of the vestibulum (which induces apparent head movement) has a comparable effect on rhythm perception and recognition (Trainor, Gao, Lei, Lehtovaara, & Harris, 2009). Trainor et al explicitly hypothesized that auditory signals are enhanced through multisensory integration with vestibular signals in the posterior parietal cortex (see also Trainor & Unrau, 2009). It should be noted, however, that the recognition choices in these studies never included the original ambiguous rhythm.…”