Foreign accent syndrome: A multimodal mapping study

Abstract 

The present study explored the functional neuroanatomy of Foreign Accent Syndrome (FAS) in an Italian native speaker who developed an altered speech rhythm and melody following a circumscribed tumour to the left precentral gyrus. Structural, functional, fibre tracking and intraoperative findings were combined. No signs of dysarthria, apraxia of speech, or aphasia nor other cognitive deficits were detected, except for the fact that the patient was perceived as a non-native speaker. The patient fMRI maps were compared with a control group of 12 healthy controls. During counting, sentences and pseudoword pronunciation the patient showed an additional increased sparse activation in areas around the pre/postcentral gyrus corresponding to those involved in phonation (i.e., larynx motor area). The intraoperative cortical stimulation mapping evidenced a mouth motor representation close to the tumour, a motor type of speech arrest site just below it, and anteriorly a proper speech arrest site. Our results are discussed within the current neurolinguistic models of speech production, and emphasize the importance of the primary motor cortex. We argue that this FAS case should be thought of as a disorder of the feedforward control commands, in particular of the articulator velocity and position maps which are hypothesized to lie along the caudoventral portion of the precentral gyrus.

Keywords: Foreign Accent Syndrome, Premotor cortex, Multimodal mapping, fMRI, Awake surgery, Speech articulation