Sound Localization and the Auditory Cortex

This chapter reviews the representation of sound-source locations in the auditory cortex. It begins with a description of the spatial sensitivity of single neurons, beginning with the primary auditory cortex (A1) in cats and ferrets, and then reviewing recent surveys of the second auditory area (A2), the anterior ectosylvian sulcus area, the anterior auditory field, the posterior auditory field, and the dorsal zone of A1. Topics include spatial receptive fields, spatial topography, spatial sensitivity in anesthetized-versus-unanesthetized conditions, responses to dynamic sounds and multiple sound sources, derivation of spatial sensitivity from acoustic cues, and responses in nonhuman primates. Next, the problem is addressed as to how an animal, or an investigator, might identify the location of a sound source strictly on the basis of patterns of cortical activity. The effects of cortical inactivation on sound-localization behavior are reviewed, including studies using classical lesion techniques as well as newer reversible inactivation techniques. Finally, the role of the human auditory cortex in sound localization is addressed in the context of the clinical lesion literature supplemented by modern structural imaging techniques and in the context of the rapidly emerging use of functional imaging.