Neural Entrainment to Auditory Imagery of Rhythms

Abstract

A method of reconstructing perceived or imagined music by analyzing brain activity has not yet been established. As a first step toward developing such a method, we aimed to reconstruct the imagery of rhythm, which is one element of music. It has been reported that a periodic electroencephalogram (EEG) response is elicited while a human imagines a binary or ternary meter on a musical beat. However, it is not clear whether or not brain activity synchronizes with fully imagined beat and meter without auditory stimuli. To investigate neural entrainment to imagined rhythm during auditory imagery of beat and meter, we recorded EEG while nine participants (eight males and one female) imagined three types of rhythm without auditory stimuli but with visual timing, and then we analyzed the amplitude spectra of the EEG. We also recorded EEG while the participants only gazed at the visual timing as a control condition to confirm the visual effect. Furthermore, we derived features of the EEG using canonical correlation analysis (CCA) and conducted an experiment to individually classify the three types of imagined rhythm from the EEG. The results showed that classification accuracies exceeded the chance level in all participants. These results suggest that auditory imagery of meter elicits a periodic EEG response that changes at the imagined beat and meter frequency even in the fully imagined conditions. This study represents the first step toward the realization of a method for reconstructing the imagined music from brain activity.

A stimulus-brain coupling analysis of regular and irregular rhythms in adults with dyslexia and controls

“…To investigate whether such oscillations could be observed, Nozaradan et al (2011) presented participants with a rhythmic stimulus containing a 2.4 Hz beat frequency while participants imagined either a binary (march, 1.2 Hz) or ternary (waltz, 0.8 Hz) meter. The beat frequency and the specific imagined meter frequencies (march or waltz) were represented in the oscillatory brain activity, showing that the neural oscillations were tracking both the physically present beat frequency, and the frequency of a meter that was not physically present in the stimulus but was being imagined by the participants (see similar results in Okawa, Suefusa, & Tanaka, 2017). However, such methods have been questioned as proof of neural entrainment, as the act of directing attention toward an imagined meter or beat may also enhance evoked potentials, and could therefore be misinterpreted as entrainment (e.g., Novembre & Iannetti, 2018).…”

“…However, neighboring peaks (1.5 Hz and 3 Hz) with similar energy in the signal did not engender enhanced coherence in the brain for regular compared to irregular stimuli, suggesting that the 2 Hz beat level representation was more than a linear response to the acoustic energy in the stimuli. In contrast to previous research where participants were asked to imagine a given underlying meter (Nozaradan et al, 2011;Okawa et al, 2017), there was no task for participants when listening to the rhythms in the current experiment. Therefore, the enhancement of the 2 Hz beat level could not be because of an explicit instruction to direct attention to a certain beat or meter level.…”

Induced Beta Power Modulations during Isochronous Auditory Beats Reflect Intentional Anticipation before Gradual Tempo Changes

“…Also, imagined movement caused more beta ERD at the time of the movement onset 13 compared to baseline where no movement was imagined, and demanding motor imagery caused stronger beta ERD than simple motor imagery 67 . We found other EEG and MEG studies which investigated musical and temporal imagery but only evoked responses were analysed [68][69][70] . It would therefore be beneficial to specifically manipulate imagery within the temporal anticipation paradigm.…”

Music Training, Working Memory, and Neural Oscillations: A Review

“…Tapping along with music rhythms induces beat-related entrainment (Nozaradan et al, 2015) as well as changes in functional somatosensory networks (Daly et al, 2014) and behavior (Nozaradan et al, 2016;Crasta et al, 2018). Importantly, rhythm entrainment is not limited to the auditory modality (Okawa et al, 2017) and can occur in the absence of an external stimulus. For example, entrained oscillatory activity persists during brief pauses in a rhythmic pattern (Stupacher et al, 2016), and varies not only with rhythm-based predictions of directly observed sequences, but also with memory-based predictions of imagined sequences (Breska and Deouell, 2017;Okawa et al, 2017).…”

“…Importantly, rhythm entrainment is not limited to the auditory modality (Okawa et al, 2017) and can occur in the absence of an external stimulus. For example, entrained oscillatory activity persists during brief pauses in a rhythmic pattern (Stupacher et al, 2016), and varies not only with rhythm-based predictions of directly observed sequences, but also with memory-based predictions of imagined sequences (Breska and Deouell, 2017;Okawa et al, 2017). As discussed previously in this review, musicians show enhanced oscillatory activity and coherence during working memory delays, which may facilitate improved music-related error processing and pattern predictions shown in musicians compared to non-musicians (Doelling and Poeppel, 2015;Stupacher et al, 2017;Harding et al, 2019).…”