Phylogenetic reorganization of the basal ganglia: A necessary, but not the only, bridge over a primate Rubicon of acoustic communication

In this response to commentaries, we revisit the two main arguments of our target article. Based on data drawn from a variety of research areas – vocal behavior in nonhuman primates, speech physiology and pathology, neurobiology of basal ganglia functions, motor skill learning, paleoanthropological concepts – the target article, first, suggests a two-stage model of the evolution of the crucial motor prerequisites of spoken language within the hominin lineage: (1) monosynaptic refinement of the projections of motor cortex to brainstem nuclei steering laryngeal muscles, and (2) subsequent “vocal-laryngeal elaboration” of cortico-basal ganglia circuits, driven by human-specific FOXP2 mutations. Second, as concerns the ontogenetic development of verbal communication, age-dependent interactions between the basal ganglia and their cortical targets are assumed to contribute to the time course of the acquisition of articulate speech. Whereas such a phylogenetic reorganization of cortico-striatal circuits must be considered a necessary prerequisite for ontogenetic speech acquisition, the 30 commentaries – addressing the whole range of data sources referred to – point at several further aspects of acoustic communication which have to be added to or integrated with the presented model. For example, the relationships between vocal tract movement sequencing – the focus of the target article – and rhythmical structures of movement organization, the connections between speech motor control and the central-auditory and central-visual systems, the impact of social factors upon the development of vocal behavior (in nonhuman primates and in our species), and the interactions of ontogenetic speech acquisition – based upon FOXP2-driven structural changes at the level of the basal ganglia – with preceding subvocal stages of acoustic communication as well as higher-order (cognitive) dimensions of phonological development. Most importantly, thus, several promising future research directions unfold from these contributions – accessible to clinical studies and functional imaging in our species as well as experimental investigations in nonhuman primates

Role of Therapeutic Devices in Enhancing Speech Intelligibility and Vocal Intensity in an Individual with Parkinson’s Disease

The prevailing speech therapy techniques for treating hypokinetic dysarthria in individuals with Parkinson\u27s disease (PD) yields improvements within the clinical setting, however, maintenance and generalization of acquired behaviors continue to be a challenge. The purpose of this study was to investigate the effects of portable therapeutic devices including Ambulatory Phonation Monitor with biofeedback (APM) and auditory masker in maintenance and carryover of improved speech. Our participant was an individual diagnosed with PD for the past 25 years who continued to display speech disturbances despite undergoing several behavioral speech therapy programs and neurosurgical procedures. Speech intelligibility and average intensity measures under automatic, elicited, and spontaneous speech tasks were recorded pre- and postusage of APM and auditory masker for a period of 1 week each. Preliminary findings showed no significant difference in the measures between means (P\u3e0.05) across all tasks for both the devices. Suggestions for future research on therapeutic devices are discussed

The Role of Auditory Feedback for Speech Intensity Regulation in Parkinson’s Disease

Hypophonia (low speech intensity) has been found to be the most common speech symptom experienced by individuals with Parkinson’s disease (PD). Previous research suggests that, in the PD population, there may be abnormal integration of sensory information for motor production of speech intensity. In the current study, auditory feedback was systematically manipulated during sensorimotor conditions that are known to modulate speech intensity in everyday contexts. Twenty-six individuals with PD and twenty-four neurologically healthy controls were asked to complete the following tasks: converse with the experimenter with varying distances between the participant and listener (near and far distances), vowel prolongation, read sentences at a comfortable loudness, complete a magnitude production task (reading 2 times louder, 4 times louder, maximum loudness), and complete an imitation task (50dB, 60dB, 70dB, 80dB), while hearing their own speech intensity randomly altered. Altered intensity feedback conditions included 5, 10 and 15dB reductions and increases in the feedback intensity. Participants were also asked to read sentences with and without an instruction to attempt to ignore the auditory feedback. Speech tasks were completed in no noise, background noise, and a complete masking noise condition. Outcome measures included speech intensity (dB) and loudness perception ratings obtained using a visual analogue scale. Overall results indicate that individuals with PD display a reduced response to the altered intensity feedback in all speech tasks, suggestive of abnormal of processing of auditory feedback for speech intensity regulation. Specific deficits related to the perception of self-loudness are suggested based on the current findings. Clinical implications are discussed as they relate to understanding specific deficits of auditory processing for speech impairments in PD

The Basal Ganglia as a Structure of Vocal Sensory-Motor Integration and Modulation of Vocal Plasticity in Mammals: Behavioral and Experimental Evidence from Tadarida brasiliensis

The neural mechanisms underlying vocal motor control are poorly understood in mammalian systems. Particularly lacking are details pertaining to the mechanisms and neuroanatomical basis of sensory-motor integration and vocal plasticity, both of which are thought to be essential for evolutionarily advanced vocal behaviors like birdsong or human speech. Based on clinical evidence and imaging studies in humans, as well as its known significance for motor control in general, the basal ganglia (BG) have been hypothesized as a key site for audio-vocal integration, but direct evidence of this is lacking. In this dissertation, I will fill this gap by providing experimental evidence that the basal ganglia are an important component of the forebrain vocal motor pathway. First, I present two examples of vocal plasticity in Tadarida brasiliensis that can serve as powerful behavioral assays of audio-vocal integration. Secondly I provide evidence of BG functions in audio-vocal integration by knocking down striatal dopamine levels with the neurotoxin 1-methyl-4-phenyl-1,2,3,6 tetrahydropyrridine (MPTP). Finally, I will utilize the D1-type receptor specific agonist SKF82958 and antagonist SCH23390 to examine how the direct pathway of the BG regulates vocal production and sensorymotor integration. The behavioral results of these experiments indicate that the bats have a complex and context depended vocal response to noise stimuli that can be used to examine the neurological control of vocal plasticity. Further, the pharmacological evidence demonstrated that the BG was necessary for maintaining and modulating normal muscle force during vocal production. Finally, the mechanism of action in the basal ganglia was found to depend at least partly on activity at D1-type dopamine receptors. The results of this dissertation support the hypothesis that the BG is a critical structure in the modulation of vocal commands in the forebrain vocal-motor pathway. Pathological or pharmacological disruption of dopamine signaling severely degraded the bats abilities to produce natural sounding calls or make adaptive changes to the acoustic environment. These results have implications for research into the treatment of basal ganglia disorders such as Parkinson’s disease, providing an animal model for the study of hypokinetic dysarthria

Oxidative Stress and Mitochondrial Injury in Chronic Multisymptom Conditions: From Gulf War Illness to Autism Spectrum Disorder

Background: Overlapping chronic multisymptom illnesses (CMI) include Chronic Fatigue Syndrome (CFS), fibromyalgia, irritable bowel syndrome, multiple chemical sensitivity, and Gulf War illness (GWI), and subsets of autism spectrum disorder (ASD). GWI entails a more circumscribed set of experiences that may provide insights of relevance to overlapping conditions.
Objectives: To consolidate evidence regarding a role for oxidative stress and mitochondrial dysfunction (OSMD), as primary mediators in CMI, using GWI as a departure point.
Methods: Exposure relations, character, timecourse and multiplicity of symptoms, and objective correlates of GWI are compared to expectation for OSMD. Objective correlates of OSMD in GWI and overlapping conditions are examined. 
Discussion: OSMD is an expected consequence of known GWI exposures; is compatible with symptom characteristics observed; and accords with objective markers and health conditions linked to GWI, extending to autoimmune disease and infection. Emergent triangulating evidence directly supports OSMD in multisymptom “overlap” CMI conditions, with similarities to, and diagnosed at elevated rates in, GWI, suggesting a common role in each. 
Conclusions: GWI is compatible with a paradigm by which uncompensated exposure to oxidative/nitrative stressors accompanies and triggers mitochondrial dysfunction, cell energy compromise, and multiple downstream effects such as vulnerability to autoantibodies. This promotes a profile of protean symptoms with variable latency emphasizing but not confined to energy-demanding post-mitotic tissues, according with (and accounting for) known properties of multisystem overlap conditions. This advances understanding of GWI; health conditions attending GWI at elevated rates; and overlap conditions like CFS and ASD, providing prospects for vulnerability assessment, mitigation of progression, treatment, and future prevention – with implications germane to additive and excessive environmental oxidative stressor exposures in the civilian setting.
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Loudness Matching in Individuals with Parkinson’s Disease and Hypophonia

The purpose of the present study was to investigate speech loudness perception in 15 individuals with Parkinson’s disease (IWPD) and hypophonia (reduced speech intensity) and 15 healthy control (HC) participants. A loudness matching procedure was used to examine conditions involving speech loudness targets presented at various levels (60 to 80dB SPL). The loudness response conditions included manually controlled audio playback of external speech, self-vocalized speech, amplified self-speech, and speech projected to a distance of 2 meters. For most of the loudness matching conditions, the PD group did not demonstrate the predicted deficit in loudness matching. In some loudness matching conditions, the PD group had lower (more accurate) error scores than the HC group. More specifically, for most of the loudness matching conditions involving self-vocalized (imitation) responses, the PD group had significantly lower error scores than the HC group. This result is inconsistent with previous studies of speech loudness imitation in PD. In addition, the finding that a PD group had better performance than a HC group is judged to be unique in the field of speech perception and production. Factors that may have influenced these results include the ordering of experimental conditions, the facilitating effect of a preceding limb motor task, hypophonia symptom severity, and PD-related enhancement of feedback processes. Future studies are required to replicate and further examine these speech loudness matching results in IWPD and hypophonia

Models and Analysis of Vocal Emissions for Biomedical Applications

The MAVEBA Workshop proceedings, held on a biannual basis, collect the scientific papers presented both as oral and poster contributions, during the conference. The main subjects are: development of theoretical and mechanical models as an aid to the study of main phonatory dysfunctions, as well as the biomedical engineering methods for the analysis of voice signals and images, as a support to clinical diagnosis and classification of vocal pathologies

Syncope in a Population-Based Sample of Elderly Persons: Prevalence, Predisposing Risk Factors, and Precipitating Events

Syncope is a serious but potentially preventable occurrence commonly afflicting the elderly population. The objectives of this study were to estimate the incidence of syncope in the community-dwelling elderly population, to identify the clinical risk factors that predispose some elderly persons to syncope, and to describe situational factors and the morbidity associated with syncope. Study participants were members of the Project Safety cohort, representing a probability sample of non-institutionalized residents of New Haven, Connecticut aged 72 years or older. Age-restricted housing lists and utilities listings were used to generate an index of community dwellings from which 5,936 households were identified. Baseline interviews identified 1,436 eligible persons. From this group, 1,103 people were followed for a syncopal episode for a two year period. Syncope occurred in 6.3% of the subjects over the two year period. Many diverse baseline characteristics were associated with an increased risk for syncope including the presence of several chronic conditions, a history of syncope or dizziness, the use of certain medications, and impaired functional status. Clinical risk factors independently associated with syncope included a history of dizziness when rising from the sitting position (adjusted odds ratio 3.1; 95% confidence interval 1.6, 6.1), a history of syncope in past year (2.4; 1.1, 5.2), the use of glycosides, nitrates and/or calcium channel blockers (2.2; 1.3, 3.7), slow gait speed (1.5; 0.9, 2.7), and age \u3e78 years (1.5; 0.9, 2.6). Soft tissue injury was the most often reported injury while fractures were associated with 9.9% of syncopal events, representing 16% of those episodes associated with some injury. A multifactorial model for the etiology of syncope appears to best explain the occurrence of syncope in the elderly population. Therefore, a multidimensional risk strategy to stratify patients into different risk groups will enable directing risk reduction practices toward those patients who may most benefit

The effect of multitalker background noise on speech intelligibility in Parkinson\u27s disease and controls

This study investigated the effect of multi-talker background noise on speech intelligibility in participants with hypophonia due to Parkinson’s disease (PD). Ten individuals with PD and 10 geriatric controls were tested on four speech intelligibility tasks at the single word, sentence, and conversation level in various conditions of background noise. Listeners assessed speech intelligibility using word identification or orthographic transcription procedures. Results revealed non-significant differences between groups when intelligibility was assessed in no background noise. PD speech intelligibility decreased significantly relative to controls in the presence of background noise. A phonetic error analysis revealed a distinct error profile for PD speech in background noise. The four most frequent phonetic errors were glottal-null, consonant-null in final position, stop place of articulation, and initial position cluster-singleton. The results demonstrate that individuals with PD have significant and distinctive deficits in speech intelligibility and phonetic errors in the presence of background noise

Influence of ear canal occlusion and air-conduction feedback on speech production in noise

Millions of workers are exposed to high noise levels on a daily basis. The primary concern for these individuals is the prevention of noise-induced hearing loss, which is typically accomplished by wearing of some type of personal hearing protector. However, many workers complain they cannot adequately hear their co-workers when hearing protectors are worn. There are many aspects related to fully understanding verbal communication between noise-exposed workers that are wearing hearing protection. One topic that has received limited attention is the overall voice level a person uses to communicate in a noisy environment. Quantifying this component provides a starting point for understanding how communication may be improved in such situations. While blocking out external sounds, hearing protectors also induce changes in the wearer’s self-perception of his/her own voice, which is known as the occlusion effect. The occlusion effect and attenuation provided by hearing protectors generally produce opposite effects on that individual’s vocal output. A controlled laboratory study was devised to systematically examine the effect on a talker’s voice level caused by wearing a hearing protector and while being subjected to high noise levels. To test whether differences between occluded and unoccluded vocal characteristics are due solely to the occlusion effect, speech produced while subjects’ ear canals were occluded was measured without the subject effectively receiving any attenuation from the hearing protectors. To test whether vocal output differences are due to the reduction in the talker’s self-perceived voice level, the amount of occlusion was held constant while varying the effective hearing protector attenuation. Results show the occlusion effect, hearing protector attenuation, and ambient noise level all to have an effect on the talker’s voice output level, and all three must be known to fully understand and/or predict the effect in a particular situation. The results of this study may be used to begin an effort to quantify metrics in addition to the basic noise reduction rating that may be used to evaluate a hearing protector’s practical usability/wearability. By developing such performance metrics, workers will have information to make informed decisions about which hearing protector they should use for their particular work environment