Elizabeth M. Adams

An entropy-based model for basal ganglia dysfunctions in movement disorders.

During this last decade, nonlinear analyses have been used to characterize the irregularity that exists in the neuronal data stream of the basal ganglia. In comparison to linear parameters for disparity (i.e., rate, standard deviation, and oscillatory activities), nonlinear analyses focus on complex patterns that are composed of groups of interspike intervals with matching lengths but not necessarily contiguous in the data stream. In light of recent animal and clinical studies, we present a review and commentary on the basal ganglia neuronal entropy in the context of movement disorders.

Non-linear dynamics in parkinsonism

Over the last 30 years, the functions (and dysfunctions) of the sensory-motor circuitry have been mostly conceptualized using linear modelizations which have resulted in two main models: the “rate hypothesis” and the “oscillatory hypothesis.” In these two models, the basal ganglia data stream is envisaged as a random temporal combination of independent simple patterns issued from its probability distribution of interval interspikes or its spectrum of frequencies respectively. More recently, non-linear analyses have been introduced in the modelization of motor circuitry activities, and they have provided evidences that complex temporal organizations exist in basal ganglia neuronal activities. Regarding movement disorders, these complex temporal organizations in the basal ganglia data stream differ between conditions (i.e., parkinsonism, dyskinesia, healthy control) and are responsive to treatments (i.e., l-DOPA, deep brain stimulation). A body of evidence has reported that basal ganglia neuronal entropy (a marker for complexity/irregularity in time series) is higher in hypokinetic state. In line with these findings, an entropy-based model has been recently formulated to introduce basal ganglia entropy as a marker for the alteration of motor processing and a factor of motor inhibition. Importantly, non-linear features have also been identified as a marker of condition and/or treatment effects in brain global signals (EEG), muscular activities (EMG), or kinetic of motor symptoms (tremor, gait) of patients with movement disorders. It is therefore warranted that the non-linear dynamics of motor circuitry will contribute to a better understanding of the neuronal dysfunctions underlying the spectrum of parkinsonian motor symptoms including tremor, rigidity, and hypokinesia.

Effects of reverberation on acceptable noise level measurements in younger and older adults.

Abstract Acceptable noise level (ANL) test materials were digitally modified to create five reverberant conditions by applying different values of reverberation time (RT) to a non-reverberant condition (RT = 0, 0.4, 0.7, 1.2, and 2 s). Two groups of 12 subjects participated: younger individuals (22–29 years, M = 24.3) and older adults (50–69 years, M = 57.5). Mean hearing threshold levels (250 to 8000 Hz) for both groups were 30 dB HL or better. Most comfortable listening level (MCL) and background noise level (BNL) measurements were completed in each reverberant condition, and from these measurements, ANLs were calculated. Significant main effects for age and reverberation were not found for ANL or MCL. These results suggest that reverberation does not affect the amount of background noise individuals are willing to accept, or the level of speech individuals choose as the MCL. These results can be used by clinical audiologists to counsel patients regarding the use of communication strategies. Additionally, these results can be used to support previous findings that ANL is not related to the intelligibility of the speech signal. Sumario Se modificaron digitalmente materiales de prueba de niveles aceptables de ruido (ANL) para crear cinco condiciones de reverberación, aplicando diferentes valores de tiempo de reverberación (RT) a una condición no reverberante (RT = 0, 0.4, 0.7, 1.2, y 2 s). Participaron dos grupos de 12 sujetos: jóvenes (22–29 años, M = 24.3) y adultos mayores (50–69 años, M = 57.5). La media de los umbrales auditivos (250 a 8000 Hz) en ambos grupos fue de 30 dB HL o mejor. El mejor nivel confortable de audición (MCL) y las mediciones del nivel de ruido de fondo (BNL) se completaron en cada condición de reverberación y de estas mediciones, se calcularon los ANL. No se encontraron efectos significativos por edad y reverberación para el ANL o el MCL. Estos resultados sugieren que la reverberación no afecta la cantidad de ruido de fondo que los individuos stán dispuestos a aceptar ni el nivel de lenguaje que seleccionan como el MCL. Estos resultados pueden ser usados por los audiólogos clínicos para aconsejar a los pacientes en relación con el uso de estrategias comunicativas. Adicionalmente, pueden usarse para apoyar hallazgos previos en cuanto a que los ANL no se relacionan con la inteligibilidad de las señales del habla.

Effects of reverberation and filtering on speech rate judgment.

This study investigated the effects of listening condition on speech rate judgment. Four listening conditions, in which a single sentence was presented at 21 speech rates ranging from 90 wpm to 250 wpm, were incorporated. These conditions included non-degraded, reverberation, band-pass filtered, and low-pass filtered conditions, each of which was selected to simulate listening conditions one might encounter in daily life. The participants were 20 young adults (20 to 40 years) with normal hearing. They were asked to make judgments of the rates of speech randomly presented in the four listening conditions using an equal-interval 5-step scale from too slow through too fast. Overall, speech rate was judged to be faster in the reverberant condition than in the other three conditions. These findings may have implications for auditory rehabilitation and counseling.

Parkinsonian Balance Deficits Quantified Using a Game Industry Board and a Specific Battery of Four Paradigms.

This study describes a cost-effective screening protocol for parkinsonism based on combined objective and subjective monitoring of balance function. Objective evaluation of balance function was performed using a game industry balance board and an automated analyses of the dynamic of the center of pressure in time, frequency, and non-linear domains collected during short series of stand up tests with different modalities and severity of sensorial deprivation. The subjective measurement of balance function was performed using the Dizziness Handicap Inventory questionnaire. Principal component analyses on both objective and subjective measurements of balance function allowed to obtained a specificity and selectivity for parkinsonian patients (vs. healthy subjects) of 0.67 and 0.71 respectively. The findings are discussed regarding the relevance of cost-effective balance-based screening system as strategy to meet the needs of broader and earlier screening for parkinsonism in communities with limited access to healthcare.

The effect of reverberation on Quick Speech‐in‐Noise test and Revised‐Speech Perception in Noise test scores in young adults with normal hearing.

In typical, realistic listening environments, speech perception is often degraded by various degrees of both noise and reverberation. The effect of reverberation has previously been assessed with predictability measures, such as the speech transmission index (STI). [Houtgast et al. (1980); Steeneken and Houtgast (1980).] Currently, no clinical test measure of an individual’s speech perception ability incorporates both noise and reverberation. The aim of the present study is to provide a more real‐world measure of speech perception performance with the inclusion of reverberation on two speech‐in‐noise tests. The Revised‐Speech Perception in Noise Test [R‐SPIN; Bilger et al. (1984)] and the Quick Speech‐in‐Noise Test [QuickSIN; Etymotic Research (2001)] are administered in multitalker babble at various signal‐to‐noise ratios (SNRs) and reverberation times in young adults with normal hearing. Results of the QuickSIN and R‐SPIN tests indicate that reverberation negatively impacts speech perception but is depe...