Assessing Oromotor Capacity in ALS: The Effect of a Fixed-Target Task on Lip Biomechanics

Abstract

Alternating motion rate (AMR) is a standard measure often included in neurological examinations to assess orofacial neuromuscular integrity. AMR is typically derived from recordings of patients producing repetitions of a single syllable as fast and clear as possible on one breath. Because the task places high demands on oromotor performance, particularly articulatory speed, AMRs are widely considered to be tests of maximum performance and, therefore, likely to reveal underlying neurologic deficits. Despite decades of widespread use, biomechanical studies have shown that speakers often circumvent the presumed speed challenge of the standard AMR task. Specifically, speakers are likely to manipulate their displacements (movement amplitude) instead of speed because this strategy requires less motor effort. The current study examined the effectiveness of a novel fixed-target paradigm for minimizing the truncation of articulatory excursions and maximizing motor effort. We compared the standard AMR task to that of a fixed-target AMR task and focused specifically on the tasks' potential to detect decrements in lip motor performance in persons with dysarthria due to amyotrophic lateral sclerosis (ALS). Our participants were 14 healthy controls and 17 individuals with ALS. For the standard AMR task, participants were instructed to produce the syllable /bα/ as quickly and accurately as possible on one breath. For the fixed-target AMR task, participants were given the same instructions, but were also required to strike a physical target placed under the jaw during the opening phase of each syllable. Lip kinematic data were obtained using 3D electromagnetic articulography. 16 kinematic features were extracted using an algorithmic approach. Findings revealed that compared to the standard task, the fixed-target AMR task placed increased motor demands on the oromotor system by eliciting larger excursions, faster speeds, and greater spatiotemporal variability. In addition, participants with ALS exhibited limited ability to adapt to the higher articulatory demands of the fixed-target task. Between the two AMR tasks, the maximum speed during the fixed-target task showed a moderate association with the ALSFRS-R bulbar subscore. Employment of both standard and fixed-target AMR tasks is, however, needed for comprehensive assessment of oromotor function and for elucidating profiles of task adaptation.

The effects of continuous oromotor activity on speech motor learning: speech biomechanics and neurophysiologic correlates

“…This reduction of lip movement is consistent with previous research demonstrating the economization of articulator movements adopted by neurologically healthy speakers. When instructed to increase speech rate, for example, healthy individuals tend to reduce the extent of articulator displacement rather than increase movement speed (Eshghi et al 2019 ; Mefferd and Green 2010 ; Simione et al 2018 ; Westbury and Dembowski 1993 ). Additionally, children increase their speech rate throughout development by minimizing lip and jaw displacements rather than increasing their movement speed to achieve a faster speech rate (Nip and Green 2013 ); when learning novel stimuli, healthy participants minimize the extent of movement as much as possible without sacrificing achievement of task goals, i.e., accuracy/precision (Lindblom 1990 ).…”

“…Impairments in the ability to produce understandable and natural speech are caused by a variety of neurologic abnormalities (Duffy 2013) and are well-known to negatively impact quality of life (McAuliffe et al 2017;Piacentini et al 2014;Walshe and Miller 2011). Although therapies for improving the intelligibility and quality of speech are available (see Duffy 2013;Finch et al 2020;Palmer and Enderby 2007;Yorkston 2010 for overviews of available therapies), current interventions have limited effectiveness and often, do not result in complete recovery of intelligible and naturalsounding speech (Herd et al 2012;Mitchell et al 2017). In general, the field of speech-language pathology could benefit from more effective, efficient, and long-lasting therapies for improving speech in a variety of patient populations.…”

Analysing spectral changes over time to identify articulatory impairments in dysarthria

“…It would be interesting to examine the effect of articulatory complexity by employing alternating motion rate task in a follow-up study. This task is frequently used to test maximum motor performance to reveal neurological deficits and it has been shown, for example, that speakers with ALS face difficulty in adapting to the higher motor commands on the articulatory system (Eshghi et al, 2019). Depending on the type of neurogenerative disease, different levels of adaptation are expected.…”

Two Distinct Clinical Phenotypes of Bulbar Motor Impairment in Amyotrophic Lateral Sclerosis

“…Participants were asked to take a deep breath and repeat the syllable “bah” as quickly and accurately as possible, for as long as possible, on one breath. This AMR task is a maximum performance task ( 27 , 28 ) that tests the speed-generating capacity of the lips and jaw. Electromagnetic articulography (Wave; Northern Digital, Inc.) was used to track three-dimensional lip movement during the task.…”

“…The algorithm provided 21 features of lip movement during the rapid syllable repetition task. We used two articulatory parameters shown to be sensitive markers of disease progression ( 15 , 28 , 29 ): maximum velocity (mm/second) of lower lip movement (maximum velocity across the entire production) and total duration (seconds) of the syllable repetition task. An example of the lip movement analysis is displayed in Figure 1C .…”