An Echo of Consciousness: Brain Function During Preferred Music

Background Given its emotional and autobiographical properties, music appears as a potential aid in diagnostic assessment and therapeutics in patients with disorders of consciousness (DOC). Several studies have shown boosting effects on behavior and brain functioning when patients were exposed to (their preferred) music. Objective To investigate if these effects on the brain's spontaneous activity are dependent on the level of consciousness. Methods Nine post-comatose patients and eight healthy control subjects were assessed using fMRI in two conditions: rest (without stimulation) and music. All patients presented at least an auditory startle, thereby suggesting the presence of residual auditory function. A gradient of consciousness (from unresponsive wakefulness syndrome to healthy subjects) was formulated to evaluate consciousness-level-dependent increases in brain activity and connectivity. Network-based functional connectivity assessed auditory, default-mode, frontoparietal and music-evoked emotions networks. Furthermore, exploratory voxel-to-voxel analyses were performed at the whole brain level using intrinsic connectivity contrast and (fractional) amplitude of low frequency fluctuations. Results Stronger consciousness-level-dependent increases within network-to-voxel analysis of connectivity were found in the frontoparietal network with the precuneus during music stimulation compared to rest. Voxel-to-voxel analyses showed stronger increases of intrinsic connectivity in the music condition compared to rest in regions previously related to music processing. There were consistently more regions with increased connectivity during the main effect of music compared to rest. These increases of connectivity during music were observed in brain regions involved in consciousness, language, emotion and memory processing. Conclusions Our results show that music seems to trigger more substantial connectivity changes compared to rest, pointing towards the potential ability of music to stimulate patients' brain function. Further research should focus on effects of music in general, its specific acoustical features and the effects of simple auditory stimuli, as well as the possible therapeutic and diagnostic effects of music in well controlled clinical trials.