Table 1.
Parameters of heart rate variability (HRV).
Fig 1.
Stimuli and procedure of Experiment 1.
A, B, and C show 30 second samples of a triplet of corresponding acoustic stimuli used. Notice that the isochronous tones in B and C have identical tempi as the stimulus in A. D demonstrates the sequence of one trial. Twenty-five such trials with different stimuli were presented. Before and after each auditory stimulus, short sinus tone sequences (indicated by the two notes in the figure) were used to notify the subjects that a trial will start, respectively the rating procedure will follow.
Fig 2.
Heart rate results of all three Experiments.
The acoustic stimuli generally increased the heart rate compared to silence. Although interquartile ranges were relatively wide, the effects were highly significant in Experiment 1 and 3. This indicates a larger sympathetic output during the acoustic stimuli. Pleasant: pleasant music; Unpleasant: music-like noise (Exp. 1 & 3) and unpleasant music (Exp. 2); *: p < .05; ***: p < .001.
Fig 3.
Heart rate variability results of Experiment 1.
All acoustic stimuli decreased all heart rate variability parameters compared to silence except the LF/HF ratio. This is taken to indicate a reduced parasympathetic output during the acoustic stimuli. Notice that the effects with the isochronous tones, and music-like noise stimuli were qualitatively comparable to the pleasant music stimuli. Lg: indicates logarithmized data where transformation was applied; Pleasant: pleasant music; Unpleasant: music-like noise; *: p < .05; **: p < .01; ***: p < .001. For description of HRV parameters see Table 1.
Fig 4.
Electrodermal activity results of Experiment 1.
All acoustic stimuli increased the sum of electrodermal activity amplitudes compared to silence. Although interquartile ranges were relatively wide, the effects were significant. This indicates a greater sympathetic output during the acoustical stimuli. Pleasant: pleasant music; Unpleasant: music-like noise; *: p < .05; **: p < .01.
Fig 5.
Heart rate variability results of Experiment 2.
The acoustic stimuli decreased most of the heart rate variability parameters compared to silence, thus generally reproducing the results of Experiment 1. Note the similar results of the slow (90 bpm) and fast (120 bpm) versions of pleasant music and unpleasant music. This indicates that such a tempo difference does not entrain different heart rate variability. Lg: indicates logarithmized data where transformation was applied; Pleasant: pleasant music; Unpleas.: unpleasant music; *: p < .05; **: p < .01; ***: p < .001. For description of HRV parameters see Table 1.
Table 2.
Characteristics of participants in Experiment 3.
Table 3.
Clinical characteristics of Crohn′s disease patients of Experiment 3.
Fig 6.
Heart rate variability results of Experiment 3.
The acoustic stimuli decreased all heart rate variability parameters compared to silence except the LF/HF ratio, thus reproducing the results of Experiment 1 and 2. Note the generally similar results of healthy subjects and Crohn′s disease patients. This demonstrates that Crohn′s disease is not per se characterized by a different autonomic tone or autonomic reactivity. Lg: indicates logarithmized data where transformation was applied; Pleasant: pleasant music; Unpleasant: music-like noise; *: p < .05; **: p < .01; ***: p < .001. For description of HRV parameters see Table 1.
Table 4.
Summary of heart rate and heart rate variability effects of pleasant music compared to silence.
Table 5.
Summary of heart rate and heart rate variability effects of isochronous tones, music-like noise, and unpleasant music compared to silence.