Hierarchical models of processing intelligible speech. ("A") Hierarchical processing in the temporal lobe, showing a posterior-anterior gradient in acoustic insensitivity moving away from primary auditory cortex. Posterior and anterior regions of STS discussed by Okada et al. (2010) are outlined in white. ("B") An expanded model of hierarchical processing for speech that includes prefrontal, premotor/motor, and posterior inferotemporal regions.