Pitch Syntax Violations Are Linked to Greater Skin Conductance Changes, Relative to Timbral Violations - The Predictive Role of the Reward System in Perspective of Cortico-subcortical Loops.

Edward J Gorzelańczyk,Emilia Tarnowska,Maciej Karpiński,Piotr Walecki,Piotr Podlipniak

doi:10.3389/fpsyg.2017.00586

Abstract

According to contemporary opinion emotional reactions to syntactic violations are due to surprise as a result of the general mechanism of prediction. The classic view is that, the processing of musical syntax can be explained by activity of the cerebral cortex. However, some recent studies have indicated that subcortical brain structures, including those related to the processing of emotions, are also important during the processing of syntax. In order to check whether emotional reactions play a role in the processing of pitch syntax or are only the result of the general mechanism of prediction, the comparison of skin conductance levels reacting to three types of melodies were recorded. In this study, 28 subjects listened to three types of short melodies prepared in Musical Instrument Digital Interface Standard files (MIDI) – tonally correct, tonally violated (with one out-of-key – i.e., of high information content), and tonally correct but with one note played in a different timbre. The BioSemi ActiveTwo with two passive Nihon Kohden electrodes was used. Skin conductance levels were positively correlated with the presented stimuli (timbral changes and tonal violations). Although changes in skin conductance levels were also observed in response to the change in timbre, the reactions to tonal violations were significantly stronger. Therefore, despite the fact that timbral change is at least as equally unexpected as an out-of-key note, the processing of pitch syntax mainly generates increased activation of the sympathetic part of the autonomic nervous system. These results suggest that the cortico–subcortical loops (especially the anterior cingulate – limbic loop) may play an important role in the processing of musical syntax.

Highlights

Tonal music is a natural, and complex syntactic system (Lerdahl and Jackendoff, 1983) based on implicitly learned norms (Tillmann et al, 2000; Tillmann, 2005)
It has been observed that the mean skin conductance value in response to tonal violations is significantly higher in musical stimuli than to a change in timbre
The electro-dermal responses to tonal violations are more frequent and have a higher value in contrast to the electro-dermal response to timbral changes, listeners reported after the study that they had been more conscious of the timbral changes in comparison to tonal violations

Summary

Introduction

Tonal music is a natural, and complex syntactic system (Lerdahl and Jackendoff, 1983) based on implicitly learned norms (Tillmann et al, 2000; Tillmann, 2005). The perception of pitch structure as hierarchically organized discrete units (pitch classes) is an important part of syntactic processing in music (Krumhansl, 1990; Krumhansl and Cuddy, 2010; Lerdahl, 2013) During this process, the recognition of each pitch class in the context of other pitch classes is accompanied by subtle emotional sensations known as tension, uncertainty, stability, completion, and power, etc. According to Huron (Huron, 2006), positive emotions (e.g., the tonal qualia of resolution or completeness often described as pleasure, contentment etc.) are the result of limbic reward for accurate predictions, whereas negative emotions (e.g., the tonal qualia of tension or incompleteness often described as uncomfortable, jarring, anxious etc.) are elicited in case our predictions are inaccurate. The activity of the latter influences skin conductance (Dawson et al, 2007; Zhang et al, 2016) and other physiological parameters (Wood et al, 2014; Schröder et al, 2015)

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Conclusion