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Schlagwörter:
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Zusammenfassung:
Background
Congenital amusia, also referred to as tone-deafness, is defined as a developmental disorder affecting the perception and processing of music (Ayottte et al., 2002). It has been hypothesized that individuals with congenital amusia are born without sufficient neural correlates to perceive and process music. This might indicate that the brain network involved in music perception and processing is deficient in subjects with congenital amusias. In this study we aimed to compare the brain anatomy of amusical subjects (AS) and matched control subjects (CS). Locating and defining the anatomical markers of this disorder might help to understand the neural dysfunction.
Method
We were able to recruit subjects with congenital amusia by placing ads in local news papers and by conducting an initial telephone screening. This initial phone screening assessed musical and educational backgrounds, as well as handedness, gender and family history. After this phone screening, we tested 17 potential amusia subjects with the \x{201D}Battery of Musical Disability Tests\x{201D}, developed and standardized to diagnose amusia by Peretz and colleagues (Ayotte et al., 2002). This musical battery consists of 6 subtests testing scale, contour, interval, rhythm, metric, and memory skills in the music domain. Percent of correct answers given by our subjects were compared with a mean of 61 normal subjects (Ayotte et al., 2002). Only 8 subjects (4 male and 4 female) performed in at least two of the first three subtests (scale, contour, rhythm) below 2 standard deviations compared to that mean. We matched these 8 amusical subjects with 16 (8 male, 8 female) normal control subjects, matched for age, gender and handedness. Control subjects participated in various anatomical and functional imaging experiments in our laboratory. We acquired high-resolution anatomical data sets (voxel size 1mm3) using a 1.5T Siemens Vision MR scanner. The SPM99 software package was used for data analysis. Using established voxel-based morphometry methods, we tested for group differences in gray matter concentration.
Results
Preliminary data analysis demonstrates that AS show less gray matter in the anterior middle temporal gyrus on the right and in the left inferior frontal gyrus (p<0.005, uncorrected, extend threshold = 25 voxels). These were deemed significant after a small volume correction with a sphere of 30 mm was applied.
Discussion
These results reveal that AS show less gray matter concentration in brain regions that have been associated with musical functions such as pitch memory and melodic contour discrimination as well as rhythm and music sequencing tasks. Finding these regional differences in the gray matter concentration might indicate that the neural network of music perception and processing is deficient in subjects with congenital amusia.
References
Ayotte, J.; Peretz, I. & Hyde, K. (2002). Congenital amusia: a group study of adults afflicted with a music-specific disorder. Brain, 125, 238-251.
