Breaking the mirror: Asymmetrical disconnection between the phonological input and output codes.

In this paper, we study the link between the processing systems that sustain speech perception and production in a patient (F.A.) with conduction aphasia. Her pattern of performance in repetition task - quantitative but also qualitative striking difference in errors with pseudowords versus words - cannot be properly accounted for either by a perception deficit or by a production deficit. We discuss this finding according to theoretical models of phonological processing and show that it is best explained by an impaired ability to transfer phonological information from the perception to the production system. We also probed for a phonological link in the opposite direction, from the production to the perception system. F.A.'s results show that this link was not impaired. Overall, our results suggest that (a) the phonological codes in perception and in production are separate but connected by two conversion mechanisms and that (b) these two mechanisms can be disrupted independently.