Neural correlates of conceptualisation difficulty during the preparation of complex utterances
Abstract:Background: In language production, conceptualisation of the utterance precedes lemma retrieval, phonological encoding, and articulation. Knowledge about the neural correlates of conceptualisation is scarce. Aims: The study aimed at the delineation of neurophysiological correlates of the macro-planning aspect of conceptualisation by manipulating difficulty of conceptualisation. Methods & Procedures: Utterances were elicited by visual arrays containing a network of eight different shapes (e.g., circle, square) of different colours. Upon the appearance of an arrow in the display, participants had to describe either the direction of the arrow only (simple condition), the direction and the destination shape (medium condition), or the direction, the destination shape, and its colour (complex condition). Event-related brain potentials (ERPs) were recorded from young healthy native speakers of German and analysed for epochs starting 100 ms prior to the onset of the arrow stimulus until 600 ms thereafter, i.e., prior to the onset of the vocalisation. ERPs were quantified by mean amplitude measures. Outcomes & Results: ERPs uncontaminated by vocalisation artefacts were obtained. Brain potentials in the medium and complex conditions were more positive going than those from the simple condition from 300 ms onwards. This effect had a centro-parietal distribution akin the P300 component. Conclusions: Reliable electrophysiological effects of conceptualisation difficulty were obtained, opening new possibilities for the neurophysiological investigation of language production in healthy participants and those with non-aphasic language disorders. The distribution of the conceptualisation effect suggests that it reflects general effects of conceptualisation difficulty (e.g., demand for processing resources) rather than specific steps of the language planning process.
Document Type: Research Article
Publication date: December 1, 2007