Subthalamic Stimulation Reduces Vowel Space at the Initiation of Sustained Production: Implications for Articulatory Motor Control in Parkinson’s Disease

Abstract

Background: Stimulation of the subthalamic nuclei (STN) is an effective treatment for Parkinson’s disease, but complaints of speech difficulties after surgery have been difficult to quantify. Speech measures do not convincingly account for such reports.Objective: This study examined STN stimulation effects on vowel production, in order to probe whether DBS affects articulatory posturing. The objective was to compare positioning during the initiation phase with the steady prolongation phase by measuring vowel spaces for three “corner” vowels at these two time frames.Methods: Vowel space was measured over the initial 0.25 sec of sustained productions of high front (/i/), high back (/u/) and low vowels (/a/), and again during a 2 sec segment at the midpoint. Eight right-handed male subjects with bilateral STN stimulation and seven age-matched male controls were studied based on their participation in a larger study that included functional imaging. Mean values: age = 57±4.6 yrs; PD duration = 12.3±2.7 yrs; duration of DBS = 25.6±21.2 mos, and UPDRS III speech score = 1.6±0.7. STN subjects were studied off medication at their therapeutic DBS settings and again with their stimulators off, counter-balanced order.Results: Vowel space was larger in the initiation phase compared to the midpoint for both the control and the STN subjects off stimulation. With stimulation on, however, the initial vowel space was significantly reduced to the area measured at the mid-point. For the three vowels, the acoustics were differentially affected, in accordance with expected effects of front versus back position in the vocal tract.Conclusions: STN stimulation appears to constrain initial articulatory gestures for vowel production, raising the possibility that articulatory positions normally used in speech are similarly constrained.

Emotional prosody of Parkinsonians following subthalamic nucleus deep brain stimulation

“…The conclusion of our study is that the DBS-on state negatively influences the expression of emotional prosody in the speech of patients with Parkinson's disease. This is in accordance with results of other studies that suggest a spectrum of possible explanations, from constrained articulatory positions normally used in speech due to DBS (Sidtis, Alken, Tagliati, Alterman, & Van Lancker Sidtis, 2016) or laryngoscopic findings such as incomplete glottal closure, hyperadduction of the false vocal folds, anteroposterior hypercompression, and asymmetrical glottal movement (Tsuboi et al, 2015;Tanaka et al, 2015) to unintended activation of dorsal premotor cortex (Narayana et al, 2009).…”

Vocalic transitions as markers of speech acoustic changes with STN-DBS in Parkinson’s Disease

“…For the PD group, eight participants (5 women and 3 men) aged 53–72 years were recruited from an outpatient movement disorders clinic. While modest, subject numbers are consistent with published studies on STN-DBS from others laboratories (Dromey & Bjarnason, 2011; Sidtis, Alken, Tagliati, Alterman, & Van Lancker Sidtis, 2016). This topic is considered further in the discussion.…”

“…This terminology has been used in previously published articles (i.e. Sidtis et al, 2016) where control participants were matched to PD participants on an individual level.…”

Effect of Low versus High Frequency Subthalamic Deep Brain Stimulation on Speech Intelligibility and Verbal Fluency in Parkinson’s Disease: A Double-Blind Study

“…This is attributed to spasticity resulting from current spread to neighbouring fibres [5,40]. Sidtis, et al [41] proposed that STN-DBS alters the internal mapping of the articulators and the afferent feedback regarding their state and in doing so disrupts the co-ordination of articulatory, laryngeal and respiratory components. Studies using acoustic and aerodynamic measures demonstrate improved coordination of phonation and respiration with LFS [42].…”