ABSTRACT
Our goal in this chapter is to provide a model of the auditory system, especially at the cortical level, that is mainly based on experimental observations on monkeys but largely applies to humans. Such models or theories of subcortical and cortical processing networks have been elaborated repeatedly for the visual system (e.g., Felleman & Van Essen, 1991), and, to a lesser extent, the somatosensory system (e.g., Kaas, 2004). These models include proposed subdivisions (areas and nuclei) of systems and their interconnections. We prefer to refer to such depictions of systems as models or theories rather than descriptions because of uncertainties about interpretations of results, and the limitations of many results. In the outline of the primate visual system of Felleman and Van Essen (1991), for example, the authors indicated the locations of 32 visual areas on a surface of the flattened cortex of a macaque monkey brain, and diagramed the cortical connections of all 32 visual areas. This effort necessarily involved interpretations of the results of many studies where uncertainties exist over the locations of injection sites for revealing connections, the locations of transported label indicating projecting neurons or axon terminations, and the architectonic and physiological evidence for the areas. In recognition of these uncertainties, the authors assigned confidence levels to proposed areas from 1 to 3, with only five areas getting the rating of 1 for being well defined. However, there are even uncertainties about two of these five areas. Of these five, three (V1, V2, and MT) are widely accepted as valid visual
areas, but the other two (dorsal V3 and VP) are not (see Kaas & Lyon, 2001). Instead, V3d and VP might be parts of the same visual area.
