Friday, May 25, 2007

Dorsal & ventral streams: language-science scooped vision science

We have written that our dual stream model of speech processing builds on research on cortical models of the visual system, particularly the distinction between dorsal and ventral processing streams. And it does. But there is a much older precedent both to our own proposal, and to current dual-stream vision theories: Wernicke's classic 1874 language model. As we all know, Wernicke proposed that sensory representations of speech ("auditory word images") interfaced with two distinct systems, the conceptual system, which he believed was broadly distributed throughout cortex, and the motor system located in the frontal lobe. The interface with the conceptual system supported comprehension of speech, whereas the interface with the motor system helped support the production of speech. Thus, one stream processes the meaning of sensory information (the "what" stream), while the other allows for interaction with the action system (the "how" stream). This is basically identical to what David and I have been claiming in terms of broad organization of our dual stream model, and identical to what folks like Milner and Goodale have proposed in the vision domain. When will those vision folks get an idea of their own. ;-)

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