Rhythmogram as a tool for continuous electrographic data analysis

Ecologically relevant stimuli are rarely used in scientific studies because they are difficult to control. Instead researchers employ simple stimuli with sharp boundaries (in space and time). Here we explore how the rhythmogram can be used to provide the much needed rigorous control of natural continuous stimuli like music and speech. The analysis provides a natural way of correlating important features in the timecourse of stimuli with corresponding features in brain activations elicited by the same stimuli. Correlating the identified regularities of the stimulus time course with the features extracted from the activations of each voxel of a tomographic analysis of brain activity provides a powerful view of how different brain regions are influenced by the stimulus at different times and over different (user-selected) timescales. The application of the analysis to tomographic solutions extracted from Magnetoencephalographic (MEG) data recorded while subjects listen to music reveal a surprising and aesthetically pleasing aspect of brain function: an area believed to be specialized for visual processing is recruited to analyze the music after the acoustic signal is transformed to a feature map.