The cortical organization of speech processing: Feedback control and predictive coding the context of a dual-stream model

Speech recognition is an active process that involves some form of predictive coding. This statement is relatively uncontroversial. What is less clear is the source of the prediction. The dual-stream model of speech processing suggests that there are two possible sources of predictive coding in speech perception: the motor speech system and the lexical-conceptual system. Here I provide an overview of the dual-stream model of speech processing and then discuss evidence concerning the source of predictive coding during speech recognition. I conclude that, in contrast to recent theoretical trends, the dorsal sensory-motor stream is not a source of forward prediction that can facilitate speech recognition. Rather, it is forward prediction coming out of the ventral stream that serves this function. Learning outcomes: Readers will (1) be able to explain the dual route model of speech processing including the function of the dorsal and ventral streams in language processing, (2) describe how disruptions to certain components of the dorsal stream can cause conduction aphasia, (3) be able to explain the fundamental principles of state feedback control in motor behavior, and (4) identify the role of predictive coding in motor control and in perception and how predictive coding coming out of the two streams may have different functional consequences. (C) 2012 Elsevier Inc. All rights reserved.