Friday, October 12, 2007, 12-2 p.m.

The Cortical Organization of Speech Processing

Despite decades of research, the functional neuroanatomy of speech processing has been difficult to characterize.  A major impediment to progress may have been the failure to consider task effects when mapping speech-related processing systems.  We outline a dual-stream model of speech processing that remedies this situation. In this model, a ventral stream processes speech signals for comprehension, and a dorsal stream maps acoustic speech signals to frontal lobe articulatory networks.  The model assumes that the ventral stream is largely bilaterally organized, although there are important computational differences between the left and right hemisphere systems, whereas the dorsal stream is strongly left-hemisphere dominant. The model has fairly broad implications, touching on work in speech development, clinical aphasia, verbal working memory, sentence-level processing, and sensory-motor integration in other sensory systems.