Right fronto-parietal white matter disruption contributes to speech impairments in amyotrophic lateral sclerosis

INTRODUCTION Non-linguistic properties of speech are widely heterogeneous and require complex neurological integration. The association between white matter integrity and the severity of dysarthria was investigated in a group of patients diagnosed with amyotrophic lateral sclerosis (ALS). METHODS Thirty-six patients diagnosed with amyotrophic lateral sclerosis completed a magnetic resonance imaging protocol inclusive of diffusion-weighted images. A clinical assessment of pneumo-phono-articulatory abilities was conducted for each patient, and a composite score of residual speech capacity was calculated. Tract-Based Spatial Statistics was carried out to model the potential association between residual speech capacity and microstructural properties of white matter (fractional anisotropy, mean and radial diffusivity). RESULTS A significant negative association was found between residual speech capacity and mean diffusivity in a large white matter cluster located in frontal, parietal and right temporal regions. These subcortical areas were characterised by pathological microstructural disruption, as revealed bypost hoc analyses. CONCLUSIONS Non-linguistic aspects of speech are associated with microstructural integrity of frontal, parietal and right temporal white matter in amyotrophic lateral sclerosis. Such mapping is consistent with the centres responsible of volitional control of speech and sensory feedback during non-linguistic speech production

Human larynx motor cortices coordinate respiration for vocal-motor control.

Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. This ability is supported in part by the evolution of a direct neural pathway linking the motor cortex to the brainstem nucleus that controls the larynx the primary sound source for communication. Early brain imaging studies demonstrated that larynx motor cortex at the dorsal end of the orofacial division of motor cortex (dLMC) integrated laryngeal and respiratory control, thereby coordinating two major muscular systems that are necessary for vocalization. Neurosurgical studies have since demonstrated the existence of a second larynx motor area at the ventral extent of the orofacial motor division (vLMC) of motor cortex. The vLMC has been presumed to be less relevant to speech motor control, but its functional role remains unknown. We employed a novel ultra-high field (7T) magnetic resonance imaging paradigm that combined singing and whistling simple melodies to localise the larynx motor cortices and test their involvement in respiratory motor control. Surprisingly, whistling activated both 'larynx areas' more strongly than singing despite the reduced involvement of the larynx during whistling. We provide further evidence for the existence of two larynx motor areas in the human brain, and the first evidence that laryngeal-respiratory integration is a shared property of both larynx motor areas. We outline explicit predictions about the descending motor pathways that give these cortical areas access to both the laryngeal and respiratory systems and discuss the implications for the evolution of speech

Human larynx motor cortices coordinate respiration for vocal-motor control

Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. This ability is supported in part by the evolution of a direct neural pathway linking the motor cortex to the brainstem nucleus that controls the larynx the primary sound source for communication. Early brain imaging studies demonstrated that larynx motor cortex at the dorsal end of the orofacial division of motor cortex (dLMC) integrated laryngeal and respiratory control, thereby coordinating two major muscular systems that are necessary for vocalization. Neurosurgical studies have since demonstrated the existence of a second larynx motor area at the ventral extent of the orofacial motor division (vLMC) of motor cortex. The vLMC has been presumed to be less relevant to speech motor control, but its functional role remains unknown. We employed a novel ultra-high field (7T) magnetic resonance imaging paradigm that combined singing and whistling simple melodies to localise the larynx motor cortices and test their involvement in respiratory motor control. Surprisingly, whistling activated both ‘larynx areas’ more strongly than singing despite the reduced involvement of the larynx during whistling. We provide further evidence for the existence of two larynx motor areas in the human brain, and the first evidence that laryngeal-respiratory integration is a shared property of both larynx motor areas. We outline explicit predictions about the descending motor pathways that give these cortical areas access to both the laryngeal and respiratory systems and discuss the implications for the evolution of speech

Brain activity during phonation in women with muscle tension dysphonia : an fMRI study

Objectives. The main objectives of this functional magnetic resonance imaging (fMRI) study are (1) to investigate brain activity during phonation in women with muscle tension dysphonia (MTD) in comparison with healthy controls; and (2) to explain the neurophysiological mechanism of laryngeal hyperfunction/tension during phonation in patients with MTD. Methods. Ten women with MTD and fifteen healthy women participated in this study. The fMRI experiment was carried out using a block design paradigm. Brain activation during phonation and exhalation was analyzed using BrainVoyager software. Results. The statistical analysis of fMRI data has demonstrated that MTD patients control phonation by use of the auditory, motor, frontal, parietal, and subcortical areas similar to phonation control by healthy people. Comparison of phonation tasks in the two groups revealed higher brain activities in the precentral gyrus, inferior, middle and superior frontal gyrus, lingual gyrus, insula, cerebellum, midbrain, and brainstem as well as lower brain activities in the cingulate gyrus, superior and middle temporal gyrus, and inferior parietal lobe in the MTD group. No differences were found between the two groups regarding exhalation control. Conclusions. The findings in this study provide insight into phonation and exhalation control in patients with MTD. The imaging results demonstrated that in patients with MTD, altered (higher/lower) brain activities may result in laryngeal tension and vocal hyperfunction

CENTRAL NEURAL AND BEHAVIORAL CORRELATES OF VOICE SECONDARY TO INDUCED UNILATERAL VOCAL FOLD PARALYSIS

Understanding the involvement of the central nervous system (CNS) in voice production is essential to incorporating principles of neuroplasticity into therapeutic practice for voice disorders. Early steps to attaining this goal require the identification of specific neural biomarkers of the changes occurring in the CNS from a voice disorder and its subsequent treatment. In the absence of an adequate animal vocalization model, the larynx has not been acutely and reversibly perturbed to concurrently examine the effect on both peripheral and central processing of the altered input/output. Using a unique, reversible perturbation approach, it was the purpose of this study to perturb the larynx to mimic a voice disorder and study short-term neuroplastic response. Functional magnetic resonance imaging (fMRI) was the neuroimaging tool of choice for this study due to its superior spatial and temporal resolution. The voice was perturbed by anesthetizing the right recurrent laryngeal nerve, with a solution of lidocaine hydrochloride and epinephrine to induce a temporary right vocal fold paralysis. The paralysis lasted for approximately 90 minutes and had an overt presentation similar to that of a true vocal fold paralysis. Behavioral and fMRI data were obtained at three time points- baseline, during the vocal fold paralysis and one hour after recovery. Patterns of activity on fMRI during the three time points were found to be distinct on both subjective examination and statistical analysis. The regions of interest examined had distinct trends in activity as a function of the paralysis. Interestingly, males and females responded differently to the paralysis and its subsequent recovery. Strong correlation was not observed between the behavioral measures and fMRI activity reflecting a disparity between the overt presentation and recovery of vocal fold paralysis and cortical activity as seen on fMRI. The fictive paralysis model employed in this study provided a perturbation model for phonation that allowed us to examine behavioral and central neural correlates for disordered phonation in a controlled environment. Although this data is representative of acute changes from a transient paralysis, it provides an insight into the response of the cortex to sudden perturbation at the peripheral phonatory mechanism

The origins of the vocal brain in humans

The evolution of vocal communication in humans required the emergence of not only voluntary control of the vocal apparatus and a flexible vocal repertoire, but the capacity for vocal learning. All of these capacities are lacking in non-human primates, suggesting that the vocal brain underwent significant modifications during human evolution. We review research spanning from early neurophysiological descriptions of great apes to the state of the art in human neuroimaging on the neural organization of the larynx motor cortex, the major regulator of vocalization for both speech and song in humans. We describe changes to the location, structure, function, and connectivity of the larynx motor cortex in humans compared with non-human primates, including critical gaps in the current understanding of the brain systems mediating vocal control and vocal learning. We explore a number of models of the origins of the vocal brain that incorporate findings from comparative neuroscience, and conclude by presenting a summary of contemporary hypotheses that can guide future researc