Speech Perception, Conduction Aphasia, and the Functional Neuroanatomy of Language

Publisher Summary This chapter explores speech perception, conduction aphasia, and the functional neuroanatomy of language. The classic functional-anatomic model of language illustrates that Broca's and Wernicke's aphasias are the only syndromes that arise from damage to an actual language processing “center.” All the rest result from the extrication of one computational system from another. Atleast one type of conduction aphasia is not a disconnection syndrome at all. A damage to the auditory word center leads to impaired comprehension because the sound pattern associated with the individual words cannot be activated; production is fluent because motor memories are preserved and they can be activated via the direct concept-to-motor pathway, but speech errors (paraphasias) are evident because the modulatory influence of auditory word representations on motor selection is lost. Word deafness is a primary aphasia resulting from damage to speech perception systems. Speech perception systems are organized bilaterally in the posterior supratemporal plane. Conduction aphasia can be viewed as a syndrome resulting from damage to these systems in the left hemisphere.