Aspectos comportamentais e eletrofisiológicos da percepção de alturas sonoras: um estudo sobre o ouvido absoluto

Abstract

In humans, the processing of sound information allowed the appearance of speech and music. The pitch - which allows the melody of a song and prosody in spoken discourse - is one of these attributes. Pitch perception is a universal skill, however, just a few individuals are able to identify or produce a tone at a particular pitch without an external tonal reference, an ability known as the Absolute Pitch (AP). However, the neural mechanisms responsible for such ability are not yet fully understood. The present work has the objective to contribute to the understanding of the neural processes involved in the perception of pitch in AP possessors. In the first study, we evaluated AP prevalence in a local population of musicians (School of Music, UFRN). For this, we used psychophysical tools and a questionnaire. This first work showed that AP is not an "all-or-nothing" process, but rather that it has different levels of performance: from people that perform below chance, until it increases gradually to 100% of correct answers. While traditional thresholds (~85%) showed a prevalence of AP similar to that observed in musicians in Europe and the United States, the application of a statistical threshold resulted in the detection of a greater number of individuals with some degree of AP. In addition, we showed that AP possessors hit more the natural notes (those with the whitekeys of the piano) than those that are accidental (flat or sharp, i.e. the black keys of the piano). We also observed that AP possessors present an earlier onset of musical training. Finally, we showed that AP was more prevalent in a high proficiency group in comparison to the average proficiency group. In a second study, we used the auditory brainstem evoked potentials (ABR) to quantify the activation of brainstem nuclei in the processing of heights of individuals with OA. In this work, we showed that sustained responses (but not the transient ones) present a higher energy in individuals with AP than in control musicians. We also found that the amplitude of this sustained response correlates with the reaction time in a pitch naming test. These results suggest that individuals with AP have an increased refinement in the processing of acoustic information in the early stages of auditory processing, which would thus contribute to a greater automation of pitch identification. We believe that this thesis will contribute to the understanding of the relationship between nervous system development and musical learning, thus contributing to the development of new music teaching techniques and training programs.