Neural correlates of cognitive decline in ALS: an fNIRS study of the prefrontal cortex.

Functional near infrared spectroscopy (fNIRS) is a clinically feasible functional neuroimaging modality for detecting early cortical changes due to neurodegenerative diseases that affect cognition. The objective of this preliminary investigation was to test for reduced prefrontal activity in persons with cognitive impairments due to amyotrophic lateral sclerosis (ALS). Participants were required to complete two N-back working memory tasks of increasing complexity during fNIRS recordings. Five participants with ALS and age- and gender-matched healthy participants comprised the experimental and control groups, respectively. Significant reductions in prefrontal oxygenation levels were observed for the left and right hemispheres in the ALS group compared to the control group. Reduced prefrontal activation despite intact behavioral performance for a working memory task may suggest early neuroanatomical, neurophysiological and/or compensatory mechanisms in affected individuals. The fNIRS-derived oxygenation measure shows promise as a sensitive neural marker to identify early neuropsychological impairments due to ALS.

Bulbar and speech motor assessment in ALS: challenges and future directions.

Bulbar motor deterioration due to amyotrophic lateral sclerosis (ALS) leads to the eventual impairment of speech and swallowing functions. Despite these devastating consequences, no standardized diagnostic procedure for assessing bulbar dysfunction in ALS exists and adequate objective markers of bulbar deterioration have not been identified. In this paper, we consider objective measures of speech motor function, which show promise for forming the basis of a comprehensive, quantitative bulbar motor assessment in ALS. These measures are based on the assessment of four speech subsystems: respiratory, phonatory, articulatory, and resonatory. The goal of this research is to design a non-invasive, comprehensive bulbar motor assessment instrument intended for early detection, monitoring of disease progression, and clinical trial application. Preliminary data from an ongoing study of bulbar motor decline are presented, which demonstrate the potential clinical efficacy of the speech subsystem approach.

Spatiotemporal coupling of the tongue in amyotrophic lateral sclerosis.

PURPOSE: The primary aim of the investigation was to identify deficits in spatiotemporal coupling between tongue regions in amyotrophic lateral sclerosis (ALS). The relations between disease-related changes in tongue movement patterns and speech intelligibility were also determined. Methods The authors recorded word productions from 11 individuals with ALS with mild, moderate, and severe dysarthria using an x-ray microbeam during word productions. A coupling index based on sliding window covariance was used to determine disease-related changes in the coupling between the tongue regions across each word. RESULTS: The results indicated decreased spatiotemporal coupling of mid-posterior tongue regions and reduced tongue speed in the ALS-moderate subgroup. Changes in the range of tongue coupling relations and speed of movement were highly correlated with speech intelligibility. CONCLUSIONS: These results provide new insights into the loss of lingual motor control due to ALS and suggest that measures of tongue performance may provide useful indicators of bulbar disease severity and progression.

Effect of speech rate manipulations on articulatory dynamics in severe traumatic brain injury: an EMA and EPG study.

BACKGROUND: Manipulation of speech rate forms an integral part of the treatment of dysarthria and the effects of changes in speech rate on articulatory dynamics in persons with traumatic brain injury (TBI) is poorly documented. OBJECTIVE: To determine the effects of manipulations of speech rate (habitual vs fast) on lingual kinematics and tongue-to-palate contacts in adult speakers with severe TBI and matched normal controls. MATERIALS AND METHODS: Six adults with severe TBI and five matched non-neurologically impaired controls underwent testing of their articulatory function using electromagnetic articulography (EMA) and electropalatography (EPG). RESULTS: The results demonstrated that the TBI and control groups selected different strategies for increasing speech rate, with the TBI group showing an increase in articulatory effort estimated from an increase in maximum velocity and maximum acceleration/deceleration of tongue movement when speaking at the fast rate. The control group demonstrated no effects of a fast speech rate on articulatory kinematics for sentence productions. CONCLUSIONS: When speaking at a fast rate, individuals with severe TBI appear to use greater articulatory effort, possibly to preserve the distinctiveness of phonetic segments in order to avoid articulatory undershoot. In contrast, control subjects show a greater economy of effort when speaking at a fast rate, possibly to preserve articulatory precision.

Electropalatographic (EPG) assessment of tongue-to-palate contacts in dysarthric speakers following TBI.

The aim of the investigation was to compare EPG-derived spatial and timing measures between a group of 11 dysarthric individuals post-severe TBI and 10 age- and sex-matched neurologically non-impaired individuals. Participants of the TBI group were diagnosed with dysarthria ranging from mild-to-moderate-severe dysarthria. Each participant from the TBI and comparison group was fitted with a custom-made artificial acrylic palate that recorded lingual palatal contact during target consonant production in sentence- and syllable-repetition tasks at a habitual rate and loudness level. Analysis of temporal parameters between the comparison and TBI groups revealed prolonged durations of the various phases of consonant production, which were attributed to articulatory slowness, impaired speech motor control, impaired accuracy, and impaired coordination of articulatory movements in the dysarthric speakers post-TBI. For the spatial measurements, quantitative analysis, as well as visual inspection of the tongue-to-palate contact diagrams, indicated spatial aberrations in dysarthric speech post-TBI. Both the spatial and temporal aberrations may have at least partially caused the perceptual judgement of articulatory impairments in the dysarthric speakers.

Electromagnetic articulography assessment of articulatory function in adults with dysarthria following traumatic brain injury.

PRIMARY OBJECTIVE: To explore articulatory kinematic differences between normal and dysarthric speakers post-traumatic brain injury (TBI) during syllable and sentence productions. RESEARCH DESIGN: A comparison between the control, mild (MTBI) and severe TBI groups for all measured kinematic parameters was carried out using the Kruskal Wallis test. METHODS AND PROCEDURES: Ten participants with a severe TBI and six post-MTBI formed the experimental group. The control group consisted of 14 age and sex matched non-neurologically impaired speakers. Articulatory kinematic profiles for the three groups were obtained using the Electromagnetic Articulograph (EMA) while repeating sentence and syllable embedded /t/ and /k/ productions at a habitual rate and loudness level. MAIN OUTCOMES AND RESULTS: Significant differences between the severe TBI and control group were identified only for the release phase of the /t/ sentence productions wherein an increase in mean maximum acceleration was observed for the severe TBI group. CONCLUSIONS: While a simple syllable repetition task at a moderate rate was unable to differentiate the three groups, a complex sentence production task precipitated an increase in mean maximum acceleration which may be indicative of increased articulatory effort and impaired speech motor control even at a convenient rate for the severe group.

EMA assessment of tongue-jaw co-ordination during speech in dysarthria following traumatic brain injury.

PRIMARY OBJECTIVE: To investigate the spatio-timing aspects of tongue-jaw co-ordination during speech in individuals with traumatic brain injury (TBI). It was hypothesized that both timing and spatial co-ordination would be affected by TBI. RESEARCH DESIGN: A group comparison design wherein Mann-Whitney U-tests were used to compare non-neurologically impaired individuals with individuals with TBI. METHODS AND PROCEDURES: Nine non-neurologically impaired adults and nine adults with TBI were involved in the study. Electromagnetic articulography (EMA) was used to track tongue and jaw movement during /t/ and /k/, embedded in sentence and syllable stimuli. MAIN OUTCOMES AND RESULTS: Analysis of group data did not reveal a significant difference in spatio-timing tongue-jaw co-ordination between the control group and TBI group. On an individual basis, a proportion of individuals with TBI differed from non-neurologically impaired participants with regard to articulatory order and percentage of jaw contribution to /t/. CONCLUSIONS: EMA assessment results supported perceptual data; those adults who presented with severe articulatory disturbances exhibited the most deviant spatio-timing tongue-jaw co-ordination patterns. This finding could provide a new and specific direction for treatment, directed at combined movement patterns.