Contributions of Subcortical and Cortical Circuitries in Complex Auditory Learning

Northwestern University, Evanston IL

Investigators

Abstract

The ability to produce and understand the intricacies of human speech has a large impact on quality of life. Auditory communication often involves learning; for example, identifying a new friend's voice over the telephone, perceiving and producing words in a foreign language, or understanding the meaning of words used in different contexts. The traditional view of the auditory system emphasizes a feed forward pathway starting from the inner ear in the cochlea, progressing to the various brainstem nuclei, the thalamus, and finally up to the auditory cortex. As acoustical and/or functional complexities of the auditory signal increase, the more likely ?higher-level? structures are to be involved. Although the existence of this corticofugal (descending) system is acknowledged in the literature, relatively little research, especially in terms of physiology, has been conducted. The functions of individual auditory-neural structures have been studied in isolation yet researchers lack an understanding of the simultaneous contributions of these structures in performing auditory functions in humans. With support from the National Science Foundation, Dr. Patrick Wong and his research team will explore whether learning speech (particularly the lexical tones of Mandarin) and music can result in changes in lower level circuitry, which could potentially then influence processing upstream that is associated with auditory encoding. Investigations on brain anatomy and physiology will be conducted using brainstem electrophysiologic and functional magnetic resonance imaging (fMRI) procedures at various time points in a training paradigm, in which participants will learn to use pitch patterns to identify English pseudo words. This study contributes to the ongoing effort to explore the plasticity of lower and higher level structures across different stages of learning, and how these functions may differ in successful and less successful learners. This research will lead to a more comprehensive understanding of brain plasticity as it pertains to auditory learning. On a broader level, this research is directly relevant to music and foreign language instruction. Regarding clinical applications, this research may shed light on hearing-related disorders which occur throughout the auditory pathway (e.g., peripheral hearing loss and central processing disorders). Additionally, the research focuses on a type of language (tone language) that is spoken natively in many parts of the world. The topic of second language learning is also important to global competitiveness, and this research should lead to improvements in our understanding of the process of learning Mandarin tones.