Cortical pitch representations of complex tones in musicians and non-musicians

Musicians typically show enhanced pitch-discrimination ability compared to non-musicians, consistent with the fact that musicians are more sensitive to some acoustic features critical for both speech and music processing. However, it is still unclear which mechanisms underlie this perceptual enhancement. In a previous behavioral study, musicians showed an increased pitch-discrimination performance for both resolved and unresolved complex tones suggesting an enhanced neural representation of pitch at central stages of the auditory system. The aim of this study was to clarify whether musicians show (i) differential neural activation in response to complex tones as compared to non-musicians and/or (ii) finer fundamental frequency (F0) representation in the auditory cortex. Assuming that the right auditory cortex is specialized in processing fine spectral changes, we hypothesized that an enhanced F0 representation in musicians would be associated with a stronger right-lateralized response to complex tones compared to non-musicians. Fundamental frequency (F0) discrimination thresholds were obtained for harmonic complex tones with F0s of 100 and 500 Hz, filtered in either a low or a high frequency region to vary the resolvability of audible harmonics. A sparse-sampling eventrelated functional magnetic resonance imaging (fMRI) paradigm was used to measure neural activation in all listeners while performing the same pitch-discrimination task for conditions of varying resolvability. The task difficulty was individually adjusted according to the previously obtained F0 discrimination thresholds. Preliminary results from 6 listeners (3 musicians and 3 non-musicians) showed that the behavioral discrimination thresholds of musicians were, on average, lower than the thresholds of non-musicians by about a factor of 2.3, independent of harmonic resolvability. A group analysis on the 6 listeners revealed no differential neural activation for resolved vs unresolved conditions, suggesting that cortical responses did not increase with increasing stimulus resolvability, when adjusting for the task difficulty across conditions and participants. A significant effect of processing demand, i.e., task demand estimated from both stimulus resolvability and task difficulty, was observed in both auditory cortices, with a larger neural activation in the right auditory region. Additionally, no differential activation was observed in the musicians vs. the non-musicians. Overall, these preliminary findings suggest an involvement of a postero-lateral region in both auditory cortices during a pitchdiscrimination task with conditions of varying processing demand. Cortical responses were larger in the right than in the left auditory cortex, suggesting an increasing activation of the right-lateralized pitch-sensitive cortical areas with increasing taskprocessing demand.