Abstracts

Rationale: Regions involved in language processing have been observed in the inferior part of the left temporal lobe. Although collectively labelled ‘the Basal Temporal Language Area’ (BTLA), these territories are functionally heterogeneous. They involve a posterior part activated by written words, frequently referred to as the ‘Visual Word Form Area’. More rostral regions are implicated in various speech, reading and semantic tasks. Electrical stimulation of this region has been shown to produce speech arrest. The language production processing level remains to be clarified. Methods: SEEG (StereoElectroEncephalography) was performed in two drug-resistant epileptic patients prior to epilepsy surgery. In one of them, the excellent temporal resolution of event-related potentials and the high spatial resolution of depth recordings allowed to collect novel data suggesting multimodal processing of language perception and production in BTLA. In the other one, intracerebral stimulation of this area reproduced the abnormal language traits present in spontaneous seizures. Results: Evoked potentials and induced gamma-band activity could be studied from intracranial recordings in an epileptic patient and provided direct evidence that the middle part of BTLA is sensitive to both auditory and visual language stimuli, as early as 300 ms after stimulation. In addition, spontaneous gamma band discharges recorded from this region induced a phonological jargon. In the same patient, these discharges likely disrupted the patient’s lexical semantic processing network, reducing spoken output to meaningless phoneme combination, i.e. a jargon. In another patient, direct stimulation of the same area also induced a non-word utterance (identical to her spontaneous seizures), similar to a jargonaphasia. Conclusions: This rare opportunity to study the BTLA “in vivo” in the context of transient dysfunction demonstrates its pivotal role in lexico-semantic processing for speech production. In addition, the multimodal nature of this region in speech perception is confirmed.