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Abstract:
Background
Absolute pitch is defined as the ability to identify every pitch of the Western musical scale without any external reference tone. Previous reports have shown anatomical differences between musicians with absolute pitch (AP) and musicians without absolute pitch (non-AP) (Schlaug, 2001). Whether or not these structural differences (e.g. planum temporale) are associated with functional differences in these anatomical regions or in other regions of the brain is not well examined. The purpose of our study was to compare the functional cerebral activation pattern of AP and non-AP during a pitch memory task.
Methods
Nine male musicians with AP and ten male non-AP musicians participated in this fMRI-study. AP subjects had to perform above 90% correct in established AP tests in order to be included in the AP group. In the pitch memory task, subjects listened to a sequence of 6-7 sine tones from a frequency range of 319 to 640 Hz. In response to a visual prompt, they then compared the last or second-to-last tone with the first tone and decided whether these tones were same or different. The target tones corresponded to the frequency of semitones of the Western musical scale (based on A = 440 Hz ), and micro tones were used as distractors. This auditory task was contrasted with a motor control task, where the subjects listened to silence and then pressed the right or left mouse button, in response to a visual prompt. We used a variation of a sparse temporal sampling technique with clustered volume acquisition after the auditory stimulation to avoid interference with the MR scanner noise as well as auditory masking effects.
Functional magnetic resonance (fMRI) was performed on a 1.5T Siemens Vision MR scanner using a gradient-echo EPI sequence (TE = 50 ms, effective TR = 17s, 24 axial slices acquired over 2.75s, 4x4x6mm voxel size). The SPM99 software package was used to analyze the data.
Results
Non-AP musicians showed more significant right superior parietal lobe (SPL) activation than the AP musicians (p=0.05, corrected). AP musicians showed more activation in the left superior temporal gyrus and the left superior parietal lobe (p<0.001, uncorrected). Since we had a strong prior regional hypothesis to find functional differences in the left superior temporal gyrus region, a small volume correction was applied and the left STG activation was highly significant.
Discussion
These results indicate differences in pitch memory strategies used by the two groups, depending on the AP ability. Non-APs show significantly more activation in the right SPL. The SPL is involved in spatial processing and may facilitate the matching of auditory and visual percepts, when stimuli are not treated categorically. AP musicians appear to use a different strategy involving left hemisphere structures such as the superior temporal gyrus and left SPL, possibly matching auditory percepts with verbal categories.
References
Schlaug, G. (2001). The brain of musicians. A model for functional and structural adaptation. Ann N Y Acad Sci, Jun 2001, 930, p281-99.
