Tuning-in to the beat: Aesthetic appreciation of musical rhythms correlates with a premotor activity boost

Abstract

Listening to music can induce us to tune in to its beat. Previous neuroimaging studies have shown that the motor system becomes involved in perceptual rhythm and timing tasks in general, as well as during preference-related responses to music. However, the role of preferred rhythm and, in particular, of preferred beat frequency (tempo) in driving activity in the motor system remains unknown. The goals of the present functional magnetic resonance imaging (fMRI) study were to determine whether the musical rhythms that are subjectively judged as beautiful boost activity in motor-related areas and if so, whether this effect is driven by preferred tempo, the underlying pulse people tune in to. On the basis of the subjects' judgments, individual preferences were determined for the different systematically varied constituents of the musical rhythms. Results demonstrate the involvement of premotor and cerebellar areas during preferred compared to not preferred musical rhythms and indicate that activity in the ventral premotor cortex (PMv) is enhanced by preferred tempo. Our findings support the assumption that the premotor activity increase during preferred tempo is the result of enhanced sensorimotor simulation of the beat frequency. This may serve as a mechanism that facilitates the tuning-in to the beat of appealing music.

Figure 1

Structural elements of a musical rhythm and an exemplary trial sequence of both judgment tasks and the control condition. The rhythmical structure of a musical rhythm was determined by tempo (inter‐onset‐interval of beats), measure (the grouping of beats), beat subdivision (elements per beat), and rhythmic figure. In addition, instrument type was introduced to increase variety in the stimulus material. The depicted rhythm example possesses a middle tempo with three beats per measure, three elements per beat and a repetitive rhythmic figure containing a long, followed by a short interval. A variable jitter time of 2.5–4 s was followed by a task cue (1 s) and an auditory stimulus presented for 3 s. Participants were asked to press the selected response button when they had decided but still while the sound was presented. They were asked to decide whether or not the presented musical rhythm was beautiful (aesthetic judgment) or fast (tempo judgment); in the control condition, they were asked to press the left button if a white noise was interrupted by two silent gaps and the left button for three silent gaps.

Figure 2

Grouping of trials for the BOLD‐contrasts preferred vs. not preferred tempo and preferred vs. not preferred instrument. The grouping was performed according to Table II, i.e., each subjects' beta weights for tempo and instrument obtained by multiple regression (individual case models), which describe the influence of each stimulus property of the musical rhythm on individual aesthetic judgments. In subjects with negative weights for tempo, slow tempo trials were classified as preferred tempo and fast tempo were classified as not preferred tempo. In subjects with positive beta weights for tempo, fast tempo trials were classified as preferred tempo and slow tempo trials were classified as not preferred tempo. Consequently, for instance, slow tempo trials in subjects with a preference for slow tempo and fast tempo trials in subjects with a preference for fast tempo were grouped together under the condition “preferred tempo.” The trial grouping according to instrument preference followed the same logic.

Figure 3

Effects of rhythmical preference. (A) Areas elevated for rhythms judged as beautiful compared to not beautiful (beautiful vs. not beautiful rhythms in AJ; P < 0.005, corrected). Scatter diagrams indicate correlations of percentage signal changes in left PCO/PMv and ACC, as well as left and right PCO/PMv during beautiful and not beautiful judgments, respectively. Each data point represents the mean and standard error of the percent signal change for each subject and location. (B) Areas elevated for preferred tempo vs. not preferred tempo (P < 0.01, corrected). The overlap between the contrast beautiful vs. not beautiful and preferred tempo vs. not preferred tempo during the aesthetic judgment task revealed a significant activation in the left PCO/PMv (−50, 4, 12, Z = 2.72; 54 mm³). ACC = anterior cingulate cortex; ISL = inferior semilunar lobule; PCO = precentral operculum; PMv = ventral premotor cortex; SSL = superior semilunar lobule.

Figure 4

Effects of tempo preference on premotor activity: Percent signal change (% sc) for musical rhythms with preferred and not preferred tempo during the aesthetic (AJ) and tempo judgment (TJ) conditions, as well as % sc during the resting condition (RC) in the ventral premotor ROI (−50, 4, 12; identified by the overlap between the contrast preferred vs. not preferred tempo during the aesthetic judgment task and the contrast beautiful vs. not beautiful). In the timeline chart, the onset corresponds to the onset of the respective stimulus and the % sc during the AJ and TJ conditions is depicted relative to the % sc of the RC.

Figure 5

Significantly activated areas for aesthetic as opposed to tempo judgments (P < 0.005, corrected).