The functional anatomy of speech sound processing is comprised of a distributed cortical system that encompasses regions along at least two processing streams. A ventral, temporal lobe pathway primarily mediates the mapping from sound input to meaning/words. A dorsal path incorporating parietal and frontal lobes enables the sensorimotor transformations that underlie mapping to output representations. To facilitate the processing along these different dimensions, sound is analyzed in temporal chunks that permit the appropriate computations in these pathways. Data from electrophysiological (MEG) and imaging (fMRI) studies suggest that there exist privileged time scales that lie at the basis of chunking the input signals. In particular, low modulation frequencies (delta and theta bands) play a special role in the construction of auditory and audiovisual representations that form the basis for auditory cognition and speech perception.
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