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Abstract

The present work focuses on the investigation of the magnetoencephalographic auditory N1m component, with the aim of investigating the different responses to stimulus attributes: intensity (decibels), temporal distance (interstimulus intervals), dynamic range adaptation, musicality, and their relationships to each other. For the data collection of neurophysiological auditory processing (N1m), magnetoencephalographic measurements were used to gain deeper insights. In addition, the assessment of the subjects’ musicality was performed by means of a psychometric test. For the evaluation of the neurophysiological component, individual two-dipole models were created by means of source analysis. It is already widely known that stimulus attributes (intensity and temporal distance) affect the neuromagnetically measurable N1m. This effect could be replicated in the present study. Higher interstimulus intervals, as well as an increase in stimulus intensity, lead to an enhancement of the amplitude of the MEG component (N1m). Based on these findings, the dynamic range adaptation of the auditory N1m component was analyzed. For this purpose, within constant intensity tone trains (high vs. low) of three consecutive stimuli, the adaptation of the N1m component to stimulus repetition was investigated. Neither of the two stimulus intensity-modulated groups showed the expected stable decrease of amplitude, which would point toward the adaptation effect within the repeated stimulus series. The expected reduction in amplitude magnitude with increasing repetition of the identical stimulus could be visualized in some conditions but did not reach statistical significance. To determine the effects of different musicality on the auditory N1m, subjects in this study were divided into two groups with high and low musicality (high vs. low AMMA total score). Analysis of the two groups failed to detect any effect of musicality on the expression of the amplitude of the N1m. Finally, the interaction between dynamic range adaptation and musicality (high vs. low) was investigated. Within the two groups with different expressions of musical performance, the dynamic range adaptation of the individual stimulus sequences (within the high- vs. low-intensity group) was examined. Here, no adaptation effects of amplitude expression could be detected as well between the three consecutively presented tones within a stimulus intensity level.

Contrary to the original expectation, apart from the stimulus intensity effects as well as the interstimulus interval effects, no adaptation effects of the N1m component could be measured in the context of dynamic range adaptation. It is possible that the longer interstimulus intervals used in this study contribute to this negative result since, by this time, a possible adaptation might already have been completed. Also, the musicality of the subject groups did not lead to changes in the measured neuromagnetic component. Consequently, it can be concluded that musicality has no effect on components localized in the planum temporale. Thus, contrary to the pitch center in lateral Heschl’s Gyrus, N1m in the planum temporale does not seem to be affected by the musicality. Consistent with these results, the interaction effects examined between dynamic range adaptation and musicality also showed no statistical relevance. In order to deeply understand the emergence and impact of adaptation effects in the context of dynamic range adaptation as well as the relevance of musicality, further research should focus on a stronger differentiation of the dipole model and the measured musicality performance.