THE ROLE OF THE OUTPUT PHONOLOGICAL BUFFER IN THE CONTROL OF SPEECH TIMING - A SINGLE-CASE STUDY

A patient with a selective impairment of speech output, associating ph onemic paraphasias and pervasive preverbal pauses, is described. Exper imental data are discussed in relation to current models of speech pro duction. On clinical evaluation, the pattern of paraphasias was strong ly suggestive of a functional lesion affecting the output phonological buffer. This hypothesis received substantial support from a study of word and non-word repetition, as well as from a study of picture namin g latencies, with various imposed delays between stimulus presentation and vocal response. In order to determine the origin of the preverbal pauses, the patient was also submitted to other timed motor tasks imp licity probing higher levels of word production (gender decision and p honemic matching). We suggest that the pauses probably resulted from t he conjunction of several mechanisms, including a general slowing appa rent in all timed motor tasks, as well as a more specific time lag in speech initiation originating from the output buffer or from the artic ulator itself.