Mixed transcortical aphasia: Repetition without meaning

Although mixed transcortical aphasia (MTA) is a rare syndrome, it constitutes an interesting case for modern neuroanatomically driven language models. This is because its existence may be seen as congruent with the assumption of an independently operating “dorsal stream” in language processing. Predicted by the earliest models of language processing in the brain, the syndrome also pushes the boundaries of neurolinguistic model building because its symptoms arise from an interplay between partially preserved linguistic functions and partially disrupted amodal higher- order cognitive control mechanisms. In summarizing 15 case reports of persons with MTA, this chapter provides details about neurobiological underpinnings, performance during standard language assessments, and speech characteristics of persons diagnosed as having MTA. The chapter raises critical issues, such as the question of how to operationalize “spared repetition,” and the difficulty of clearly differentiating between volitional repetition and nonvolitional echolalia. Data on the evolution of the syndrome are included, and assessment as well as treatment of MTA are discussed.