ABSTRACTS

Functional Activation Mapping of Human Brain During Music Imagery Processing

W. Chen, T. Kato, X.-H. Zhu, G. Adriany and K. Ugurbil CMRR, University of Minnesota, School of Medicine, Minneapolis, MN55455, USA

Introduction The ability to perceive and enjoy the music is an inborn trait in humans. Patient studies with temporal lobe lesions relative to the deficit in auditory perception and imagery were reported(I-3). However, many questions still remain about why music has a magic influence in human life and how it works in human brain. However full neuroanatomical mapping of the human brain, especially in brainstem areas, involved in the music processing is not well demonstrated. Recently, we used high filed fMRI to map the functional activation in haman brain during music imagery. Subjects were asked to imagine a classic music. The purposes of this study focused on: (a) the functional pathway and neuroanatomical connection during music imagery; Co) the functional asymmetry involved in music information processing and (c) the possibility that music imagery shares the similar substrates with auditory perception. Methods fMRI experiments were performed on a 4 Tesla whole body MP-J system. Contiguous, multislice BOLD based fMRI images (TE = 25 ms; 50 ms/each image; 64x64 pixels; FOV -- 24x24 cm2; slice thickness = 5 or 6 ram) were obtained using a blipped EPI technique. Three control and two task periods were designed in an interleaved way. A total of 100 sets of images were collected. The activation maps were generated by the period cross correlation method(4). The subjects were asked to image music sound during the task periods and to relax and not to imagine any components involving music and visual pictures during the control periods. The music sound was restricted to that which was familiar to the subjects but without any verbal meaning in order to exclude the possible involvement of language component. All imagery experiments were performed in a completely dark room and with subjects eyes closed. Four healthy subjects participated this study and five fMRI experiments were performed. Results and Discussions The activation in the primary auditory cortex (area 42) was detected bilaterally with slightly more activation in the right hemisphere during the music imagery task. The activation in the auditory association cortex (area 22) was dominated in the right temporal lobe. This clearly indicates that the functional asymmetry of the human brain due to musical information processing and the right temporal area, especially area 22, are involved in music processing. This result is consistent with the reports from patient study(I-3). The bilaterally activation in medial geniculate nucleus (MGN)were observed for the first time in the human brain by tzking advantage of high spatial resolution and high sensitivity of fMRI on a high magnetic field. During music imagery task, the pnlvinar which is near by the MGN, the inferior collicnlus and lateral lemniscus areas were also activated for most subjects. This activation route which connected lateral lernniscus, inferior coUicnlus, MGN and primary auditory cortex during music imagery is exactly the same as the route for ascending auditory pathway during perception and it supports the idea that music imagery and perception share the same substrates. The reticular formation, dorsomedial nucleus also showed activation during task which may related to the auditory awareness and attention. Also putamen showed dominated activation in left hemisphere. It is expected that putamen involves the timing information process during music imagery. Strong activation in thalamus (bilateral) and hypothalamus (more fight hemisphere) were observed during music imagery. The activation in the hypothalamus was much stronger than that shown in the visual imagery m~k(5). It is well known that although the hypothalamus composes only <0.5% of the brain weight, it is involved in nearly all aspects of behavior (e.g., emotion). It is probable that hypothalamus plays an important role in connecting music processing (imagery or perception) with the spontaneous body response. This may be the key to understand the magic of the music. This hypothesis was supported by our observation of activation in amygdala on right hemisphere which was connected to the hypothaiamus through the fiber projections. It was reported that left amygdala may involve sadness(@ Our results reveal the lateralization of emotion function and that the right amygdala may involve the happiness. Activation in the primary visual cortex and the lateral genicnlate nucleus was also observed. In addition, many activated areas in parietal, temporal and frontal cortices were detected by tMRI mapping during music imagery. Conclusions The activation in cortices and small nuclei in the human brain during music imagery was successfully mapped for the first time using fMRI technique. The main results from our preliminary work demonstrate (a) the right temporal lobe contributes to music processing; Co) music imagery and music perception share the same auditory ascending pathway and (c) the brainstem, especially hypothzlzmus, plays very important role in music information processing. Acknowledgment Supported by NIH grant RR08079. References (1) Kester, D.B. et al., Neuropsychologia. 1991, 29: 703-708. (2) Zatorre. R.J. et al., Neuropsychologia. 1993, 31: 221-232. (3) Samson, S. et al., Neuropsychologia. 1994, 32: 231-240. (4) Bandettini, P.A. et al., Math. Resort. Med. 1993, 30: 161-173. (5) Chert, W. et al., Abstract Book of 2nd FMHB, 1996. (6) Grodd, W. et al., Radiologe. 1995, 35" 283-289.

$205