Neural Activity in Spasmodic Dysphonia Patients with Tremor Study | John Houde, PhD, University of California – San Francisco
A team led by Dr. John Houde is using brain imaging to look at neural activity in patients with SD and SD with tremor. By comparing activity between SD and SD with tremor the hope was to find the abnormal brain activity unique to vocal tremor and increase understanding of this condition. They used magnetoencephalography (MEG) to look at brain activity during vocalization in patients with SD, including those with vocal tremor. To date, they have run the tests on 15 SD-only patients, two that have SD plus tremor and 12 control subjects and have found a number of interesting and unexpected findings. Following voice onset, somatosensory areas were more active in patients than controls. When they perturbed the pitch heard by subjects as they vocalized, researchers found that the brain areas responding to this perturbation were also more active in patients than controls. These results are consistent with the hypothesis that speakers with SD are hypersensitive to their sensory feedback (both somatosensory and auditory) as they vocalize.
However, Dr. Houde’s team also found a more unexpected result. Prior to the glottal positioning that precedes vocalization, they found that motor areas were actually less active in patients than controls. Thus, although speakers with SD appear to have overactive responses to sensory feedback during vocalization, they appear to be abnormally underactive when they prepare to vocalize. Their goal is to recruit and run at least 10 more SD patients who also have vocal tremor, in order to see how their pattern of neural activation differs in their experiments from the pure SD patients.