Effects of linguistic and musical expertise on early auditory processing : electrophysiological and behavioral evidence

The auditory system can be shaped by exposure to different auditory environments, such as native language and musical training, and these effects have been demonstrated at behavioral, cortical, and subcortical levels. However, it is not yet understood how these effects could be modulated by musical expertise within different linguistic groups. Thus, the main objective for this thesis was to investigate interacting effects of native language patterns and musical experience on early auditory processing of basic sound features. Methods included electrophysiological brainstem recording as well as a set of behavioral auditory discrimination tasks designed to find discrimination thresholds for intensity, frequency, and duration in single-feature conditions, and for intensity and duration in multifeature conditions. A musical sophistication self-report questionnaire was also used in correlational analyses. Native Finnish speakers showed enhanced subcortical duration processing compared to native German speakers. For Finnish speakers, musical expertise was associated with enhanced behavioral frequency discrimination. Greater musical sophisticaton was also associated with a greater decrement in perceptual duration discrimination in a complex multifeature task. Mandarin speaking musicians showed enhanced perceptual discrimination for both frequency and duration compared to Mandarin speaking nonmusicians. However, there was no difference between Mandarin speaking musicians and nonmusicians in subcortical onset responses or either of two measures of subcortical pitch tracking. Perceived intensity, frequency, and duration are related, but intensity and frequency give independent contributions to perceived duration. The results suggest that musical expertise does not enhance all auditory features equally for all language speakers; native language phonological patterns may modulate the enhancing effects of musical expertise on specific features. The perceptual effects of musical expertise were not reflected in brainstem responses, indicating that native language experience may apply a subcortical ceiling effect on the auditory features encoded in the language, and/or that musical expertise and task relevance can give additional perceptual benefits. This supports the idea that musical expertise encourages efficient processing of complex sounds in a natural sound environment, as in music performance or conversational speech, and that the sensitive nature of plasticity of the efferent pathway has a significant effect on basic auditory processing.