Hierarchical organization of the human auditory cortex revealed by functional magnetic resonance imaging

The concept of hierarchical processing-that the sensory world is broken dow n into basic features later integrated into more complex stimulus preferenc es-originated from investigations of the visual cortex. Recent studies of t he auditory cortex in nonhuman primates revealed a comparable architecture, in which core areas, receiving direct input from the thalamus, in turn, pr ovide input to a surrounding belt. Here functional magnetic resonance imagi ng (fMRI) shows that the human auditory cortex displays a similar hierarchi cal organization: pure tones (PTs) activate primarily the core, whereas bel t areas prefer complex sounds, such as narrow-band noise bursts.