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Event Detail Information
Event Detail Information
Linguistic Seminar: Prof. Torrey Loucks, UIUC Speech and Hearing Science: "Automatic Processes underlying Fluency and Speech Coordination: Individual Differences, Disorders and Compensation"
Speaker Prof. Torrey Loucks, UIUC Speech and Hearing Science
Date Sep 27, 2012
Time 4:00 pm - 5:00 pm
Location Lucy Ellis Lounge, Foreign Languages Bldg.
Event type seminar
Originating Calendar Linguistics Event Calendar
Research over the past decade has re-opened the window on sensorimotor processes that influence speech production. In a broad sense, these findings have settled the polarized debate of whether sensory input is even used in the control of ongoing speech production. After demonstrating the active role of sensory input, work is now focusing on the extent to which specific sensory inputs influence production, the direction of sensorimotor modifications and more recently on individual differences. There is some consensus that sensory alterations affect non-volitional or automatic mechanisms that regulate speech production. More recent work suggests compensations may be language-specific and/or occur across a limited range that maintains phonetic boundaries. In my own work, understanding these automatic mechanisms is central to unraveling how disfluencies emerge in people who stutter. For the most part these studies have involved subtle manipulations that may not even be detected consistently by the speaker. In my lab, we have instead used the more global manipulation of delayed auditory feedback (DAF) to study individual differences in sensorimotor compensations. DAF elicits compensation in all speakers that mostly involve fluency changes, but the range and degree of effects are not uniform. By studying a large group of typical speakers (n=100), we characterized susceptibility to rate changes, linguistic disfluences, stuttering-like disfluencies and speech errors.When the paradigm was applied to adults who stutter, we found unexpectedly that most are highly susceptible to increased disfluencies, errors and slower rates under DAF. But this does not indicate that disfluency perturbations are exclusively sensorimotor. Another possibility is that DAF acts as a cognitive distractor as subjects attend to their altered speech. To test this possibility we compared a divided attention task with DAF. Either divided attention or DAF strongly affected speech rate but only DAF caused speech errors or disfluencies. When individual susceptibility was compared, it was clear that the effects of divided attention on individuals were independent to that of DAF. We propose that realistic models of speech fluency shoul encompass cognitive and sensorimotor mechanisms. As such a potent perturbation, long-latency DAF could mask specific aspects of sensorimotor transformations caused by shorter latency DAF. Our follow-up studies used shorter delay times that begin to alter speech during the second syllable of an utterance. DAF of 25 ms slightly slowed rate but importantly reduced the velocity and amplitude of labial movements. Speech movement coordination was further altered but to a more pronounced degree in adults who stutter. These short latency effects on speech kinematics are consistent with non-volitional articulatory control mechanisms. Our ongoing work is studying how altered sensory input interacts with complex and novel speech tasks.