Research On Brain Mechanism Of Musical Improvisation

Music has a long history.The production and development of music are closely related to humans and their brain activities.Musical improvisation,an advanced cognitive activity of music,is an important model to investigate the brain-music interaction and the plasticity of the brain.Nowadays,it has been extensively paid attention on by musicians,psychologists and scientists.However,the results of the relative studies are dispersed,and the brain mechanism of musical improvisation is far from clear.One of the important reasons may be that the previous researches of musical improvisation were subjected by musical performers,such as pianists.Considering that the performance and the improvisation are two different stages in a musical activity,it is better to study the musical improvisation under the participation of composers than that of performers.Composers,who have experienced the improvisational training for a long time,are more professional to organize the complex musical material.In this paper,we used electroencephalograph(EEG)and Magnetic Resonance Image(MRI)to explore the brain mechanism of musical improvisation from multiaspects,under the participation of composers.In this dissertation,we collected the structural images,the resting-state and improvising-state functional images from 29 composers by using MRI.Meanwhile,we collected the structural images and the resting-state functional images from 31 nonmusicians as the control group.Besides,simultaneously EEG-fMRI signal from one composer was acquired to generate the brain music for further analysis.Firstly,we used MRI to study the resting-state functional network of the composers’ brain.The results showed the networks of emotion,working memory and motion were affected by the long-term training of musical improvisation.We computed the functional connectivity networks of the composer group and the control group by the method of functional connectivity density.Compared to the control group,decreased functional connectivity networks in the composer group were found in the regions of left putamen and its adjacent regions,the regions of right thalamus and its adjacent regions.Meanwhile,enhanced functional connectivity in the composer group were found in the regions of anterior cingulate cortex and its adjacent regions,the regions of left putamen,left hippocampus and left precentral cortex,and the regions of left thalamus,bilateral insula and bilateral ventral putamen.These results were the evidence for the functional plasticity of the brain caused by musical improvisation.They could also reveal that the functions of emotion,working memory and motion were engaged in the processing of musical improvisation.Secondly,based on the MRI experiment of different improvisational tasks and behavioral data,we investigated whether multiple-demand system was involved in musical improvisation,and explored its role during musical improvisation.In the study,we recruited 29 composers to improvise a piece of music by imagery according to different visual cues.Compared to the baseline,the results showed the multiple-demand system could be activated when improvising with both an unfamiliar cue and a familiar cue.Discussion was made in the aspects of the innovation on musical material,working memory and attention.Besides,compared to improvising with familiar cues,intraparietal sulcus within the multiple-demand system was found to be more involved when improvising with unfamiliar cues.We could infer that the manipulation of musical transposition was highly occurred under the unfamiliar condition.In addition,we also found that the musical improvisational level was positively correlated with the activated level of the multiple-demand system,indicating the level of the improvisation can affect the participation of the multiple-demand system.Moreover,compared to the control group,the covariance of the cortical thickness in the composer group was more significant between the multiple-demand system and other brain regions,probably due to the longterm improvisational training.In the last part,we explored the brain mechanism of musical improvisation from the view of brainwave music.In the beginning,a new method to improve the scale-free brainwave music was developed.The new music was made by simultaneously recorded EEG and fMRI signals.The mapping rule of the new EEG-fMRI brainwave music indicated as follows.The amplitude of EEG was translated to the pitch according to the power law followed by both of them.The period of an EEG waveform was mapped to the duration of a musical note.The simultaneously recorded fMRI signal followed by power law was used to control the intensity.The piano was selected as the timbre.After the test,we found the new EEG-fMRI brainwave music can make a better balance between the physiological characters and musical characters.Afterwards,we recruited one composer to participate in our next experiment,of whom simultaneously EEG and fMRI signals were recorded under the resting state and the improvising state,respectively.Then,two pieces of EEG-fMRI brainwave music in different states were made by the new method.Results showed a higher emotional arousal in the improvising-state music.Therefore,the brainwave music research could provide a new perspective for understanding the brain mechanism of musical improvisation.This paper studied the brain mechanism of musical improvisation by using the multimodal methods of behavior,EEG and MRI.Focused on the resting-state functional network,multiple-demand system and the brain music.We tried to make a step ahead on the brain mechanism of musical improvisation,which was the advanced and complex activities.These results are helpful to understand the effects on musical plasticity in the brain and enrich the research ideas of creative activities.Besides,they can provide more evidence for brain-music interaction,and also supply more potential applications for guiding music education,developing creative thinking and affecting music therapy.