Poster A56, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
The Role of Cortico-Subcortical Loops in the Learning of Speech Motor Sequences
Snežana Todorović1,2,3, Valérie Chanoine1,2,3, Andrea Brovelli4, Jean-Michel Badier5, Sonja A. Kotz6, Elin Runnqvist1,3;1Aix-Marseille Université, 2Institute of Language, Communication and the Brain, Aix-en-Provence, 3Laboratoire Parole et Langage (UMR 7309), Aix-en-Provence, 4Institut de Neurosciences de la Timone, Marseille, 5Institut de Neurosciences des Systèmes (UMR 1106), Marseille, 6Basic & Applied NeuroDynamics Laboratory, Maastricht University
Despite their central role for speaking, the neural mechanisms sustaining speech motor sequence learning are still not fully understood. The Medial frontal cortex (MFC), the Basal Ganglia (BG), and the Cerebellum (CB) seem to play a central role during the acquisition of skills that are related to, part of, or a prerequisite for speech motor sequence learning. Interestingly, one of a few studies that directly examined the neural correlates of speech motor sequence learning (Segawa et al., 2015) observed activation in the BG and MFC during speech motor sequence learning, while lack of activation in the cerebellum was attributed to statistical power. One plausible cognitive account for the common activation of BG, CB, and MFC is that all three are involved in learning but in different stages. There is evidence for the CB being more active in the earlier phases and BG in the consolidation phase in motor sequence learning, and the pre-supplementary motor area in MFC is found to be more strongly activated in the production of speech sequences in earlier phases of learning. An alternative explanation for the co-activation of the three areas is that they form a functional network. This is consistent with a growing body of evidence on the reciprocal structural and functional connectivity between BG, CB, and MFC. This empirical background raises the question to what extent the three brain areas work independently, in concert, or alternate in their contribution to learning. To answer these questions, we are testing the following hypotheses: 1) All three areas will be activated during the learning of new speech motor sequences. 2) BG and CB are expected to form two pathways of ascending neuromodulatory input to MFC during speech motor sequence learning. These two cortico-subcortical loops might have different and non-interacting impact, or BG and CB may also be functionally connected. 3) We will assess whether the role of the pathways remains static over time or evolves dynamically. In a MEG experiment, participants overtly pronounce previously unknown sequences of the type CCVCC (C=consonant, V=vowel) that are either legal (control condition) or illegal in their native language after audiovisual exposure. In a behavioural experiment we established a learning curve by comparing learning of 30 or 60 repetitions in either chunking or interleaving sequences. Behavioural data consisted of utterance transcriptions that allowed categorizing correct and incorrect utterances as well as utterance duration and onset time. For the MEG data, single-trial time courses of High Gamma Activity (HGA) are estimated at the level of brain areas of interest (source-level) and the cortical networks are mapped using HGA. At the behavioral level, learning of illegal speech motor sequences can occur after 45 repetitions (approximately one hour). This allows the process of learning to be observed at the neurocognitive level from trial to trial and shed light on the brain structures and their cooperation that underpin the learning of speech motor sequences.
Themes: Language Production, Speech Motor Control
Method: Electrophysiology (MEG/EEG/ECOG)