Modulation of post-movement beta rebound by contraction force and rate of force development

Movement induced modulation of the beta rhythm is one of the most robust neural oscillatory phenomena in the brain. In the preparation and execution phases of movement, a loss in beta amplitude is observed (movement related beta decrease (MRBD)). This is followed by a rebound above baseline on movement cessation (post movement beta rebound (PMBR)). These effects have been measured widely, and recentwork suggests that they may have significant importance. Specifically, they have potential to form the basis of biomarkers for disease, and have been used in neuroscience applications ranging from brain computer interfaces to markers of neural plasticity. However, despite the robust nature of both MRBD and PMBR, the phenomena themselves are poorly understood. In this study, we characterise MRBD and PMBR during a carefully controlled isometric wrist flexion paradigm, isolating two fundamental movement parameters;force output, and the rate of force development (RFD). Our results show that neither altered force output nor RFD has a significant effect on MRBD. In contrast, PMBR was altered by both parameters. Higher force output results in greater PMBR amplitude, and greater RFD results in a PMBR which is higher in amplitude and shorter in duration. These findings demonstrate that careful control of movement parameters cansystematically change PMBR. Further, for temporally protracted movements, the PMBR can be over 7 s in duration. This means accurate control of movement and judicious selection of paradigm parameters are critical in future clinical and basic neuroscientific studies of sensorimotor beta oscillations

Regional Brain Correlates of Beta Bursts in Health and Psychosis: A Concurrent Electroencephalography and Functional Magnetic Resonance Imaging Study

Background: There is emerging evidence for abnormal beta oscillations in psychosis. Beta-oscillations are likely to play a key role in the coordination of sensorimotor information, crucial to healthy mental function. Growing evidence suggests that beta oscillations typically manifest as transient “beta-bursts” that increase in probability following a motor response, observable as Post-Movement Beta Rebound (PMBR). Evidence indicates that PMBR is attenuated in psychosis, with greater attenuation associated with greater symptom severity and impairment. Delineating the functional role of beta-bursts may therefore be key to understanding the mechanisms underlying persistent psychotic illness.Methods: We used concurrent EEG and fMRI to identify BOLD correlates of beta-bursts during the N-back working memory task and intervening rest periods in healthy participants (N = 30) and patients with psychosis (N = 48). Results: During both task-blocks and intervening rest periods, beta-bursts phasically activated regions implicated in task-relevant content, while suppressing currently tonically active regions. Patients showed attenuated PMBR that was associated with persisting Disorganisation symptoms, as well as impairments in cognition and role function. Patients also showed greater task-related reductions in overall beta-burst rate, and greater, more extensive, beta-burst-related BOLD activation.Conclusions: Our evidence supports a model in which beta-bursts reactivate latently maintained sensorimotor information and are dysregulated and inefficient in psychosis. We propose that abnormalities in the mechanisms by which beta-bursts coordinate reactivation of contextually appropriate content can manifest as Disorganisation, working memory deficits and inaccurate forward models, and may underlie a “core deficit” associated with persisting symptoms and impairment

Imaging of Flames in Cement Kilns To Study the Influence of Different Fuel Types

The cement industry aims to use an increased amount of alternative fuels to reduce production costs and CO₂ emissions. In this study three cement plants firing different kinds and percentages of alternative fuel were studied. A specially developed camera setup was used to monitor the flames in the three cement kilns and assess the effect of alternative fuels on the flame. It was found that cofiring with solid recovered fuel (SRF) would delay the ignition point by about 2 m and lower the intensity and temperature of the kiln flame compared to a fossil fuel flame. This is related to a larger particle size and moisture content of the alternative fuels, which lowers the conversion rate compared to fossil fuels. The consequences can be a lower kiln temperature and cement quality. The longer conversion time may also lead to the possibility of localized reducing conditions in the cement kiln, which can have a negative impact on the clinker quality and process stability. The burner design may alleviate some of the issues encountered with SRF cofiring. At one of the test plants the burner was changed from a design with an annular channel for axial air to a jet design. This proved to be beneficial for an early ignition and improved dispersion of the fuel and led to an increase in cement quality and higher use of SRF

Monitoring self-reported adverse events : a prospective, pilot study in a UK osteopathic teaching clinic

Background: When obtaining informed consent osteopaths should explain to patients the potential risks from treatment. However, relevant literature is lacking in this area and none relates to a teaching clinic environment. Objective: The aim of this pilot study was to explore the feasibility of conducting a survey to determine which adverse events are reported most often by patients following treatment at an osteopathic teaching clinic. Subjects and methods: Adult patients with any ‘new’ complaint (not treated by manual therapy in the previous six months) were eligible. They completed a confidential two-part self-assessment questionnaire: data were recorded immediately prior to treatment and at 10 min, 1, 2, 3 and 7 days post-treatment. Patients, at each time-point, answered a health transition question and reported ‘additional effects of treatment’ on a 15-item check-list. Treatment was delivered by final year students following normal clinic procedures. Results: Sixty-three ‘new’ patients were recruited and treated. Part I data were provided by 60 (34F, 26 M); Part II data by 52 (29F, 23 M) participants. Presenting complaints most often affected the lower back (33%) or head/neck (20%); 48% were acute. Pain (83%), stiffness (47%) and/or lack of mobility (27%) were reported before treatment, as were various concomitant symptoms (e.g. headache, light headedness, vision disturbances). Post-treatment, all but four patients reported at least one ‘additional effect of treatment’ at least once: from all 5 time-points the total number of reports was 535. Local pain, local stiffness and worsening of the presenting complaint were most common (24.3%, 18.3% and 11.8% of all reports, respectively), peaking around 2 days post-treatment; 96% of reports were rated mild or moderate. Fifty-nine percent of patients noted some improvement in the presenting complaint at 10 min; this increased to 80% at 7 days post-treatment (n=47). Conclusions: Collecting adverse events data in a busy osteopathic teaching clinic is feasible. This pilot study showed that local pain and local stiffness of slight or moderate severity are reported most often post-treatment. A validated, standardised questionnaire for monitoring adverse events is needed to facilitate the development of an evidence base for use in osteopathic training and practise

Reference layer artefact subtraction (RLAS): A novel method of minimizing EEG artefacts during simultaneous fMRI ☆

Large artefacts compromise EEG data quality during simultaneous fMRI. These artefact voltages pose heavy demands on the bandwidth and dynamic range of EEG amplifiers and mean that even small fractional variations in the artefact voltages give rise to significant residual artefacts after average artefact subtraction. Any intrinsic reduction in the magnitude of the artefacts would be highly advantageous, allowing data with a higher bandwidth to be acquired without amplifier saturation, as well as reducing the residual artefacts that can easily swamp signals from brain activity measured using current methods. Since these problems currently limit the utility of simultaneous EEG-fMRI, new approaches for reducing the magnitude and variability of the artefacts are required. One such approach is the use of an EEG cap that incorporates electrodes embedded in a reference layer that has similar conductivity to tissue and is electrically isolated from the scalp. With this arrangement, the artefact voltages produced on the reference layer leads by time-varying field gradients, cardiac pulsation and subject movement are similar to those induced in the scalp leads, but neuronal signals are not detected in the reference layer. Taking the difference of the voltages in the reference and scalp channels will therefore reduce the artefacts, without affecting sensitivity to neuronal signals. Here, we test this approach by using a simple experimental realisation of the reference layer to investigate the artefacts induced on the leads attached to the reference layer and scalp and to evaluate the degree of artefact attenuation that can be achieved via reference layer artefact subtraction (RLAS). Through a series of experiments on phantoms and human subjects, we show that RLAS significantly reduces the gradient (GA), pulse (PA) and motion (MA) artefacts, while allowing accurate recording of neuronal signals. The results indicate that RLAS generally outperforms AAS when motion is present in the removal of the GA and PA, while the combination of AAS and RLAS always produces higher artefact attenuation than AAS. Additionally, we demonstrate that RLAS greatly attenuates the unpredictable and highly variable MAs that are very hard to remove using post-processing methods

Modulation of post-movement beta rebound by contraction force and rate of force development

Movement induced modulation of the beta rhythm is one of the most robust neural oscillatory phenomena in the brain. In the preparation and execution phases of movement, a loss in beta amplitude is observed (movement related beta decrease (MRBD)). This is followed by a rebound above baseline on movement cessation (post movement beta rebound (PMBR)). These effects have been measured widely, and recent work suggests that they may have significant importance. Specifically, they have potential to form the basis of biomarkers for disease, and have been used in neuroscience applications ranging from brain computer interfaces to markers of neural plasticity. However, despite the robust nature of both MRBD and PMBR, the phenomena themselves are poorly understood. In this study, we characterise MRBD and PMBR during a carefully controlled isometric wrist flexion paradigm, isolating two fundamental movement parameters; force output, and the rate of force development (RFD). Our results show that neither altered force output nor RFD has a significant effect on MRBD. In contrast, PMBR was altered by both parameters. Higher force output results in greater PMBR amplitude, and greater RFD results in a PMBR which is higher in amplitude and shorter in duration. These findings demonstrate that careful control of movement parameters can systematically change PMBR. Further, for temporally protracted movements, the PMBR can be over 7 s in duration. This means accurate control of movement and judicious selection of paradigm parameters are critical in future clinical and basic neuroscientific studies of sensorimotor beta oscillations

Motion-related artefacts in EEG predict neuronally plausible patterns of activation in fMRI data

The simultaneous acquisition and subsequent analysis of EEG and fMRI data is challenging owing to increased noise levels in the EEG data. A common method to integrate data from these two modalities is to use aspects of the EEG data, such as the amplitudes of event-related potentials (ERP) or oscillatory EEG activity, to predict fluctuations in the fMRI data. However, this relies on the acquisition of high quality datasets to ensure that only the correlates of neuronal activity are being studied. In this study, we investigate the effects of head-motion-related artefacts in the EEG signal on the predicted T2*-weighted signal variation. We apply our analyses to two independent datasets: 1) four participants were asked to move their feet in the scanner to generate small head movements, and 2) four participants performed an episodic memory task. We created T2*-weighted signal predictors from indicators of abrupt head motion using derivatives of the realignment parameters, from visually detected artefacts in the EEG as well as from three EEG frequency bands (theta, alpha and beta). In both datasets, we found little correlation between the T2*-weighted signal and EEG predictors that were not convolved with the canonical haemodynamic response function (cHRF). However, all convolved EEG predictors strongly correlated with the T2*-weighted signal variation in various regions including the bilateral superior temporal cortex, supplementary motor area, medial parietal cortex and cerebellum. The finding that movement onset spikes in the EEG predict T2*-weighted signal intensity only when the time course of movements is convolved with the cHRF, suggests that the correlated signal might reflect a BOLD response to neural activity associated with head movement. Furthermore, the observation that broad-spectral EEG spikes tend to occur at the same time as abrupt head movements, together with the finding that abrupt movements and EEG spikes show similar correlations with the T2*-weighted signal, indicates that the EEG spikes are produced by abrupt movement and that continuous regressors of EEG oscillations contain motion-related noise even after stringent correction of the EEG data. If not properly removed, these artefacts complicate the use of EEG data as a predictor of T2*-weighted signal variation

Investigation of agglomeration and defluidization during spouted-bed gasification of high-sodium, high-sulfur South Australian lignite

The mechanisms of agglomeration and defluidization during the fluid-bed gasification of an Australian low-rank coal are investigated. Experiments were conducted in a 77 mm inner diameter spouted-bed gasifier with a high-sodium, high-sulfur coal from the Lochiel deposit in South Australia. The effect of the bed temperature, air/fuel ratio, and superficial velocity on the stable operation of the spouted bed over a 4 h period was investigated. The results of this study indicate that stable bed operation is governed by a "high-temperature defluidization limit", suggesting that defluidization can be delayed or avoided by operating the bed with high superficial velocity and/or low bed temperatures. In experiments that resulted in agglomeration and in some experiments that did not, the average particle size within the bed material had increased, which was mainly attributed to coating of mineral particles. These coated particles were observed to be more prevalent in runs that led to defluidization of the bed. Particle growth also coincided with the increased inorganic content of the bed compared to stable runs. Agglomeration and defluidization may hence be avoided or delayed by operating the bed below about 850 °C, increasing the superficial velocity of gas within the bed, or maintaining the ash content of the bed below approximately 80%, where possible. © 2011 American Chemical Society.Daniel P. McCullough, Philip J. van Eyk, Peter J. Ashman, and Peter J. Mullinge