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Electrophysiological properties of the comprehensive language paradigm (CLaP)
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Poster D2 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
Natascha Roos1, Robert Oostenveld, Vitória Piai; 1Donders Institute for Brain Cognition and Behaviour, Donders Center for Cognition, Radboud University, Nijmegen, the Netherlands, 2Donders Institute for Brain Cognition and Behaviour, Donders Center for Cognitive Neuroimaging, Radboud University, Nijmegen, the Netherlands, 3Donders Institute for Brain Cognition and Behaviour, Donders Center for Cognition, Radboud University, Nijmegen, the Netherlands Radboud University Medical Center, Donders Institute for Brain Cognition and Behaviour, Department of Medical Psychology, Nijmegen, The Netherlands
Studies investigating language commonly isolate a single language modality or process, focusing on either comprehension or production. We aim to combine both in the new Concise Language Paradigm (CLaP), tapping into processes of comprehension and production within each trial. Word retrieval has been studied with context-driven picture naming in which participants listen to an incomplete sentence that is followed by a picture that concludes the sentence; the sentence preceding the picture is either constrained or unconstrained. In CLaP we added experimental conditions of auditory time-reversed sentences and scrambled pictures, the latter created by diffeomorphic transformation, making them unrecognizable without changing basic visual properties. The trial structure is identical across conditions, presenting an auditory stimulus (constrained, unconstrained, or reversed sentences) followed by a visual stimulus that is to be named (original/normal or scrambled photographs of objects). This paradigm allows us to investigate sentence comprehension for meaningful versus time-reversed sentences, and context-driven or bare picture naming. The CLaP thereby reduces task-related confounds between conditions. Looking at cortical activity recorded with electrophysiology (EEG and MEG), context-driven picture naming yields replicable power decreases in the alpha-beta frequency range (8-25 Hz) prior to picture onset in the left hemisphere. In addition to this contrast, using the CLaP we examined ERPs locked to sentence and to picture onset to investigate neural responses to auditory speech compared to a low-level acoustic control (i.e., time-reversed sentences), and object recognition compared to a low-level control (i.e., scrambled pictures). We tested 21 young healthy speakers with EEG. Statistical comparisons were made using non-parametric cluster-based permutation. Sentence-locked ERPs revealed cortical auditory responses to constrained and unconstrained sentences (i.e., meaningful speech) between 270 and 370 ms after sentence onset, significantly differing in amplitude from the responses for time-reversed speech. Following this initial evoked response, reversed sentences significantly diverged from meaningful speech with sustained amplitude differences. We replicated the expected context effect of power decreases (8-25 Hz) during the pre-picture interval. Comparisons with low-level control reversed sentences (preceding bare picture naming) clarified that the context effect is characterised by power decreases for constrained compared to unconstrained sentences sustained throughout the interval. Picture-locked ERPs showed that visual evoked potentials (VEPs) significantly differed between conditions in the amplitude of the P2 component (200-300 ms). VEPs also differed for bare and scrambled naming in the N1 component (starting at 170 ms), whereas for constrained and unconstrained naming the amplitude differed throughout the whole VEP (100-300 ms). These results suggest that the VEP, and especially the P2 component, is modulated not only by the physical characteristics of the visual stimuli but also by lead-in sentence constraint and speech intelligibility. These first results of the CLaP show promising opportunities to use this paradigm in combination with electrophysiology. By virtue of the well-matched contrasts across conditions it allows us to further investigate language comprehension and production, and their relationship, in a well-controlled setting in neurotypical and neurological populations.
Topic Areas: Language Production, Methods