Mapping the temporal neural dynamics of speech motor processes during fluent and disfluent speech

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Speaking is something most of us do without any thought being given to the intricate and highly coordinated brain and articulatory processes involved in converting thoughts into spoken utterances. We may become  aware of some of these processes when we find ourselves less able to produce speech fluently and without hesitation. Some individuals, such as those who experience neurological disorders or who stutter, often experience significant and persistent difficulties with speaking fluently, often with devastating effects not only on their health and well-being, but also for their personal development. The aim of our research is to better understand the nature and timing of neural processes involved in the planning, preparation and execution of articulatory movements during fluent and disfluent speech. Fluent speech requires the coordination and precise timing of a large number of neural processes and muscles at millisecond speed. While research has resulted in a solid understanding of the brain anatomy underlying speech production, less is known about the timing of the neural processes involved, and even less about what causes breakdowns in speech fluency. Preliminary data suggest that such disfluencies may result from delays and breakdowns in the sequencing and timing of these very fast processes, especially when faced with complex and stressful speaking situations. Our research is aimed at investigating these neural processes in adult speakers using magnetoencephalography (MEG), a non-invasive brain imaging technique that is ideally suited for speech research because it is noise-free and allows for the use more complex and natural speech utterances. It also has excellent spatial resolution allowing for the localization of brain processes with greater precision, especially when combined with anatomical MRI scans. Functional and anatomical brain data will be collected from a large sample of adult speakers. Who will engage in several experimental tasks that either promote fluent speech production or trigger disfluent speech. The planned experiments will investigate the role and timing of preparatory speech processes, such as motor planning, pre-articulatory rehearsal and updating of speech motor plans, and how error monitoring affects these processes. The project also will investigate the effects of biological sex (male vs. female) and age (young vs. older). Our innovative approach of combining MEG and MRI will provide an opportunity to better understand and map the anatomical pathways and functional activations that control speech motor control. The functional and anatomical data generated as part of this project will allow us to update existing neural speech production models. The insights ultimately will contribute to further the development of advanced technologies, such as brain-computer interfaces, as well as in the longer term the design of more effective assessment and intervention strategies for individuals with speech disorders.