Advancing knowledge of human development, developmental disabilities, and neurodegenerative diseases.
Cerebellar damage may impair someone’s ability to adapt both the timing of speech and vocal pitch, new Waisman Center studies suggest, shedding light on the involvement of the cerebellum in speech motor control.
The Speech Motor Neuroscience Group is seeking participants who are 18-90 years old, have good hearing, and have no history of stroke, brain injury, or neurological disease. Studies last 1-2 hours and can be scheduled at your convenience. The study consists of computer-based tasks in which you would speak, type, and listen to words you …
When individuals make a movement that produces an unexpected outcome, they learn from the resulting error.
People say between 150 and 200 words a minute on average during a casual conversation.
Sensory errors induce two types of behavioral changes: rapid compensation within a movement and longer-term adaptation of subsequent movements.
Speakers were presented with different auditory perturbations to both vowels in the word “bedhead” (left panel); one vowel was altered toward the vowel /æ/ (“had”) and the other toward /ɪ/ (“hid”), with the order balanced across participants.
Individuals with cerebellar ataxia (CA) caused by cerebellar degeneration exhibit larger reactive compensatory responses to unexpected auditory feedback perturbations than neurobiologically typical speakers, suggesting they may rely more on feedback control during speech. We test this hypothesis by examining variability in unaltered speech. Previous studies of typical speakers have demonstrated a reduction in formant variability (centering) observed during the initial phase of vowel production from vowel onset to vowel midpoint.
When auditory feedback is perturbed in a consistent way, speakers learn to adjust their speech to compensate, a process known as sensorimotor adaptation. Typically, feedback perturbation experiments employ a transformation that targets a single vowel, or that affects all vowels in the same way, resulting in a uniform change across the vowel space.
When we speak, we are able to use what we hear about that speech (auditory feedback) to alter our speech movements both in real time within a single word (feedback control) as well as over longer time scales across multiple utterances (feedforward control).
“We found that the folks with cerebellar damage responded to these unpredictable changes to a larger extent than those without any damage,” says Parrell. “It was totally unexpected.”
