Speech perceived through a damaged temporal window: lessons from word deafness and aphasia

Word deafness is an intriguing neurological syndrome characterized by severe difficulties in the ability to understand or reproduce spoken language with otherwise intact speech production and nonauditory language comprehension. The disorder is of significant theoretical importance because it putatively supports the modularity of speech recognition from more central language computational networks. However, the specificity and functional locus of the processing disturbances resulting in word deafness remains unclear. This article discusses the nature and potential treatment of word deafness, with particular reference to a detailed case study (neuropsychological, neuroimaging, and event-related potential) of an adult case of Landau-Kleffner syndrome. The findings in this case suggested temporal lobe pathophysiology involving cortical mechanisms concerned with temporal processing of rapid frequency changes in sound. We propose that these deficits may impede the analysis of linguistically important transitional frequency cues in speech and account for the profound difficulties in understanding and producing speech. The implications of these findings for approaches to the treatment of word deafness are discussed.