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Functional imaging studies have delineated a "minimal network for overt speech production," encompassing mesiofrontal structures (supplementary motor area, anterior cingulate gyrus), bilateral pre- and postcentral convolutions, extending rostrally into posterior parts of the inferior frontal gyrus (IFG) of the language-dominant hemisphere, left anterior insula as well as bilateral components of the basal ganglia, the cerebellum, and the thalamus. In order to further elucidate the specific contribution of these cerebral regions to speech motor "planning," subjects were asked to read aloud visually presented bisyllabic pseudowords during functional magnetic resonance imaging (fMRI). The test stimuli systematically varied in onset complexity (CCV versus CV) and frequency of occurrence (high-frequency, HF versus low-frequency, LF) of the initial syllable. A cognitive subtraction approach revealed a significant main effect of syllable onset complexity (CCV versus CV) at the level of left posterior IFG, left anterior insula, and both cerebellar hemispheres. Conceivably, these areas closely cooperate in the sequencing of subsyllabic aspects of the sound structure of verbal utterances. A significant main effect of syllable frequency (LF versus HF), by contrast, did not emerge. However, calculation of the time series of hemodynamic activation within the various cerebral structures engaged in speech motor control revealed this factor to enhance functional connectivity between Broca's area and ipsilateral anterior insula. (Contains 3 figures and 3 tables.)

This study focuses on the distribution of hydrogen peroxide (H2O2) in the upper tropical troposphere at altitudes between 8 and 15 km based on in situ observations during the Chemistry of the Atmosphere - Field Experiment in Africa (CAFE-Africa) campaign conducted in August-September 2018 over the tropical Atlantic Ocean and western Africa. The measured hydrogen peroxide mixing ratios in the upper troposphere show a nearly uniform latitudinal distribution with locally increased levels (up to 1 ppbv) within the Intertropical Convergence Zone (ITCZ), over the African coastal area, as well as during measurements performed in proximity of the tropical storm Florence (later developing into a hurricane), indicating the influence of convective transport processes. The measurements are compared to observation-based photostationary steady-state (PSS) calculations and numerical simulations by the global EMAC model. North of the ITCZ, PSS calculations produce lower H2O2 mixing ratios relative to the observations. Here observed mixing ratios exceed the PSS calculations by up to a factor of 2. On the other hand, PSS calculations overestimate the H2O2 mixing ratios south of the ITCZ by a factor of up to 3. The significant influence of convection in the ITCZ and the enhanced presence of clouds towards the southern hemisphere indicate contributions of atmospheric transport and cloud scavenging in the probed region. Differences between H2O2 observations and simulations of local PSS indicate that convective transport in the ITCZ region and consequent redistribution of H2O2 towards the north and south impacts the spatial distribution of H2O2 in the upper troposphere. Simulations performed by EMAC analogously overestimate hydrogen peroxide levels particularly in the southern hemisphere, most likely due to underestimated cloud scavenging. Latitudinal distribution analysis indicates a gradient from the equator towards the subtropics both in the EMAC simulations and the PSS calculations. On the other hand, the measurements display nearly uniform mixing ratios of the species in the upper troposphere with a slight decrease from the ITCZ towards the subtropics, indicating a relatively low dependency on the solar radiation inclination and the corresponding photolytic activity. The highest deviations relative to the observations correspond with the underestimated hydrogen peroxide loss due to enhanced cloud presence, scavenging, and rainout in the ITCZ and towards the south. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) and hydrogen peroxide (H2O2) play a key role in atmospheric oxidation processes. They act as sources and sinks for HOx radicals (OH + HO2), with OH as the primary oxidant that governs the atmospheric self-cleaning capacity. Measurements of these species allow evaluation of global chemistry-transport models which need to account for multifarious source distributions, transport and mixing, complex photochemical reaction pathways and deposition processes. HCHO is an intermediate produced during the oxidation of VOCs and is an indicator of photochemical activity and combustion related emissions. Due to its many production pathways and its rather short lifetime of only several hours at noon, accurate modelling of this species is challenging. In this study, we use in situ observations in the marine boundary layer (MBL) to evaluate results of the general circulation model EMAC (ECHAM5/MESSy2 Atmospheric Chemistry). The dataset was obtained during the AQABA ship campaign around the Arabian Peninsula in summer 2017. This region is characterized by high mixing ratios of photochemical air pollution, high humidity and strong solar irradiation, especially in the area around the Suez Canal and the Arabian Gulf. We find that EMAC fails to predict absolute mixing ratios of HCHO, especially during high pollution events, but it reproduces most of the HCHO variability seen in the different regions, while it systematically overestimates H2O2. This is mainly attributed to missing primary VOC emissions and the overestimation of HOx radicals, and also related to the models coarse spatial resolution. [ABSTRACT FROM AUTHOR]

Changes in speech rate have long been identified as a prominent sign of dysarthria. At the same time, such changes have been reported in the literature on normal aging. This [...]

Delayed auditory feedback (DAF) has been assessed as a rate reduction and intelligibility enhancing tool in patients with Parkinson disease (PD) for some time. However, there are contradictory results in [...]

The present study combines functional magnetic resonance imaging (fMRI) and reaction time (RT) measurements to further elucidate the influence of syllable frequency and complexity on speech motor control processes, i.e., overt reading of pseudowords. Tying in with a recent fMRI-study of our group we focused on the concept of a mental syllabary housing syllable sized ready-made motor plans for high- (HF), but not low-frequency (LF) syllables. The RT-analysis disclosed a frequency effect weakened by a simultaneous complexity effect for HF-syllables. In contrast, the fMRI data revealed no effect of syllable frequency, but point to an impact of syllable structure: Compared with CV-items, syllables with a complex onset (CCV) yielded higher hemodynamic activation in motor “execution” areas (left sensorimotor cortex, right inferior cerebellum), which is at least partially compatible with our previous study. We discuss the role of the syllable in speech motor control. [ABSTRACT FROM AUTHOR]

Measures of performance rates in speech-like or volitional nonspeech oral motor tasks are frequently used to draw inferences about articulation rate abnormalities in patients with neurologic movement disorders. The study objective was to investigate the structural relationship between rate measures of speech and of oral motor behaviors different from speech. A total of 130 patients with neurologic movement disorders and 130 healthy subjects participated in the study. Rate data was collected for oral reading (speech), rapid syllable repetition (speech-like), and rapid single articulator movements (nonspeech). The authors used factor analysis to determine whether the different rate variables reflect the same or distinct constructs. The behavioral data were most appropriately captured by a measurement model in which the different task types loaded onto separate latent variables. The data on oral motor performance rates show that speech tasks and oral motor tasks such as rapid syllable repetition or repetitive single articulator movements measure separate traits. [ABSTRACT FROM AUTHOR]