Rhythmogram-based analysis for continuous electrographic data of the human brain.

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 much needed rigorous control of natural continuous stimuli like music and speech. The analysis correlates important features in the time course 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 data recorded while subjects listen to music reveals 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. The methodology is ideal for exploring processing of complex stimuli, e.g., linguistic structure and meaning and how it fails, for example, in developmental dyslexia.