Play it by ear: up and down the keyboard, an fMRI study

Next to the manifestation of sensori-motor transformations such as singing and dancing, the ability to play an instrument by ear must rely on a unique convergence of cerebral functions involving motor preparation and auditory perception. In this study, we aimed to gain insight into the extent to which auditory perception is used to activate cerebral regions implicated in bimanual keyboard performance. Cerebral activations were studied first in 12 improvising organists (IMP) and 12 musically-unskilled controls (CTRL) while listening to two-part ‘inventions’. Subjects listened to 24 familiar and 24 unfamiliar excerpts. In two tasks, they were instructed either to imagine performing the excerpt (IMAG), or to judge its performance (JUDG). In a sparse-sampling paradigm, 3T fMRI was used to measure group- , task- , and familiarity-induced BOLD response. Comparing IMP to CTRL revealed bilateral activation of auditory and ventral PMC during IMAG and JUDG, regardless of familiarity, but no significant activation of left parietal cortex. Significant activations were found in right anterior parietal cortex and, during IMAG, posterior superior parietal. Masking IMAG by JUDG revealed extensive, exclusively right-hemisphere, activations, including dorsal en ventral PMC, posterior superior and anterior parietal cortex. Subsequently, IMP were compared to non-improvising pianists (NON) revealing significant activation of right auditory cortex and SMA in both tasks. Within-group comparison of IMAG to JUDG revealed significant right-hemisphere parietal activations in IMP, contrasted with solely left-hemisphere parietal activations in NON. Again, masking IMAG by JUDG revealed significant right-hemisphere activation of superior posterior parietal cortex as a characteristic group difference. The right-lateralised parietal activations found in IMP in this study, are possibly a manifestation of mental rotation from vertical pitch space to horizontal keyboard space. Robust, task-independent auditory activations suggest bottom-up processing of music, particularly in IMP. Bilateral activation of ventral PMC suggests a role for the mirror neuron system.