Coordination patterns in Essential Tremor patients with Deep Brain Stimulation: Syllables with low and high complexity

This study investigated syllable coordination patterns in Essential Tremor (ET) patients treated with Deep Brain Stimulation (DBS) by using electromagnetic articulography. We analyzed articulatory timing patterns for nine ET patients with activated and inactivated DBS and compared them to a group of healthy age-matched controls. We focused on timing patterns among gestures in syllables with low and high complexity in natural sentence production (simple CV versus complex CCV syllables). These articulatory patterns were interpreted in the framework of a coupled oscillator planning model of speech timing. In simple CV syllables, ET patients did show a similar coordination pattern to healthy control speakers. However, when complexity increased, the patients showed deviant coordination patterns for complex CCV syllables. These deviant patterns even aggravated under activated stimulation. We were able to show that the behavior of the speech system changes when the stimulation was activated, inducing a change in the dynamical system the ET patients have to adapt to. We conclude that coordination problems are not categorical but gradient in nature, pointing to the fact that there are dynamic mechanisms of regulation behind phonetic realization of phonological syllable parses.