Cortical Activity during Music Perception; Comparing Musicians and Non-musicians.

摘要

Musicians devote many hours and extensive effort to their music training, often from an early age. This dissertation research investigates how musical training modifies the way the brain responds to musical events. Using behavioral and event-related brain potential (ERP) measurements, the responses of musicians and non-musicians to irregularities of pitch and rhythm in unfamiliar pairs of melodies based on Western classical rules were recorded. Results indicate that musical training is associated with changes in brain processing involving the detection of both pitch and rhythm irregularities. Behaviorally, musicians detected both types of deviations significantly better than non-musicians. Moreover, musicians did not show ear preference to pitch or rhythm deviations while non-musicians demonstrated left ear advantage to both pitch and rhythm changes. These findings suggest that musicians may engage both hemispheres in response to pitch and rhythm irregularities whereas non-musicians rely preferentially on the right hemisphere for detecting rhythm and pitch deviations. Auditory evoked potentials occurring during the first ∼300 ms (N150/P300 in the case of pitch and N100/P200 in the case of rhythm) were also significantly enhanced in amplitude in musicians compared to non-musicians. ERP findings also provided additional evidence for lateralization effects not seen in the behavioral data.;The behavioral and brain responses to the same musical irregularities of pitch and rhythm were also assessed in a group of patients. This group consisted of subjects with a hearing disorder, auditory neuropathy (AN), affecting both perception of frequency and temporal cues. The sites of lesions were pre-synaptic in one subject, affecting the synapse between inner hair cell and auditory nerve; and postsynaptic in three subjects, affecting the auditory nerve. The pre-synaptic subject had 14 years of music training and the post-synaptic subjects were untrained. In the post-synaptic subjects perception of both pitch and rhythm irregularities were gravely impaired and no auditory cortical potentials were observed to the deviations. In the pre-synaptic case, perception of pitch and rhythm deviations was intact and amplitudes of evoked potentials to deviations were similar to other musicians. Overall, the results demonstrate that processing of pitch and rhythm is affected by musical training in specific ways providing evidence that long-term music training is associated with cortical plasticity and brain lateralization of musical processing.