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J Neurosci Methods [journal]
- Multimodal detection of head-movement artefacts in EEG. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 16.
Artefacts arising from head movements have been a considerable obstacle in the deployment of automatic event detection systems in ambulatory EEG. Recently, gyroscopes have been identified as a useful modality for providing complementary information to the head movement artefact detection task. In this work, a comprehensive data fusion analysis is conducted to investigate how EEG and gyroscope signals can be most effectively combined to provide a more accurate detection of head-movement artefacts in the EEG. To this end, several methods of combining these physiological and physical signals at the feature, decision and score fusion levels are examined. Results show that combination at the feature, score and decision levels are successful in improving classifier performance when compared to individual EEG or gyroscope classifiers, thus confirming that EEG and gyroscope signals carry complementary information regarding the detection of head-movement artefacts in the EEG. Feature fusion and the score fusion using the sum-rule provided the greatest improvement in artefact detection. By extending multimodal head-movement artefact detection to the score and decision fusion domains, it is possible to implement multimodal artefact detection in environments where gyroscope signals are intermittently available.
- Feedback Control of Electrode Offset Voltage in Functional Electrical Stimulation. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 16.
Control of the electrode offset voltage is an important issue related to the processes of functional electrical stimulation because excess charge accumulation over time damages both the tissue and the electrodes. This paper proposes a new feedback control scheme to regulate the electrode offset voltage to a predetermined reference value. The electrode offset voltage was continuously monitored by a sample-and-hold (S/H) circuit throughout the stimulation and non-stimulation periods. The stimulation current was then adjusted using a proportional-integral (PI) controller to minimize the error between the reference value and the electrode offset voltage. During the stimulation period, the electrode offset voltage was held by the S/H circuit, and the amplitude of the stimulation current was not affected by the PI controller. In contrast, during the non-stimulation period, the electrode offset voltage was sampled by the S/H circuit and rapidly regulated by the PI controller. Experimental results obtained using a nerve cuff electrode showed that the electrode offset voltage was successfully controlled in terms of the performance specifications such as the steady- and transient-state responses and the constraint of the controller output. Therefore, the proposed control scheme can potentially be used in various nerve stimulation devices and applications requiring control of the electrode offset voltage.
- Real-time automated spectral assessment of the BOLD response for neurofeedback at 3 and 7T. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 15.
Echo-planar imaging is the dominant functional MRI data acquisition scheme for evaluating the BOLD signal. To date, it remains the only approach providing neurofeedback from spatially localized brain activity. Real-time functional single-voxel proton spectroscopy (fSVPS) may be an alternative for spatially specific BOLD neurofeedback at 7T because it allows for a precise estimation of the local T2* signal, EPI-specific artifacts may be avoided, and the signal contrast may increase. In order to explore and optimize this alternative neurofeedback approach, we tested fully automated real-time fSVPS spectral estimation procedures to approximate T2* BOLD signal changes from the unsuppressed water peak, i.e. lorentzian non-linear complex spectral fit (LNLCSF) in frequency and frequency-time domain. The proposed approaches do not require additional spectroscopic localizers in contrast to conventional T2* approximation based on linear regression of the free induction decay (FID). For methods comparison, we evaluated quality measures for signals from the motor and the visual cortex as well as a real-time feedback condition at high (3T) and at ultra-high (7T) magnetic field strengths. Using these methods, we achieved reliable and fast water peak spectral parameter estimations. At 7T, we observed an absolute increase of spectra line narrowing due to the BOLD effect, but quality measures did not improve due to artifactual line broadening. Overall, the automated fSVPS approach can be used to assess dynamic spectral changes in real-time, and to provide localized T2* neurofeedback at 3 and 7T.
- An Automatic Rat Brain Extraction Method Based on a Deformable Surface Model. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 14.
Extraction of the brain from the skull in medical images is a necessary first step prior to image registration or segmentation. While pre-clinical MR imaging studies on small animals, such as the rat, are on the rise, fully automatic imaging processing techniques that are specific to small animal studies are still lacking. In this paper, we present an automatic rat brain extraction method, Rat Brain Deformable model method (RBD), which adapts the popular human brain extraction tool (BET) by incorporating information on brain geometry and MR image characteristics of the rat brain. The robustness of the method was demonstrated on T2-weighted MR images of 64 rats and compared with other brain extraction methods (BET, PCNN, PCNN-3D). Results demonstrate that RBD reliably extracts the rat brain with high accuracy (>92% volume overlap) and is robust against signal inhomogeneity in the images.
- FACS binding assay for analysing GDNF interactions. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 10.
Glial cell-line derived neurotrophic factor (GDNF) is a secreted protein with great therapeutic potential. However, in order to analyse the interactions between GDNF and its receptors, researchers have been mostly dependent of radioactive binding assays. We developed a FACS-based binding assay for GDNF as an alternative to current methods. We demonstrated that the FACS-based assay using TGW cells allowed readily detection of GDNF binding and displacement to endogenous receptors. The dissociation constant and half maximal inhibitory concentration obtained were comparable to other studies using standard binding assays. Overall, this FACS-based, simple to perform and adaptable to high throughput setup, provides a safer and reliable alternative to radioactive methods.
- Mathematical methods to model rodent behavior in the elevated plus-maze. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 7.
The elevated plus maze is a widely used experimental test to study anxiety-like rodent behavior. It is made of four arms, two open and two closed, connected at a central area forming a plus shaped maze. The whole apparatus is elevated 50cm from the floor. The anxiety of the animal is usually assessed by the number of entries and duration of stay in each arm type during a 5-min period. Different mathematical methods have been proposed to model the mechanisms that control the animal behavior in the maze, such as factor analysis, statistical inference on Markov chains and computational modeling. In this review we discuss these methods and propose possible extensions of them as a direction for future research.
- Examining the inflammatory response to nanopatterned polydimethylsiloxane using organotypic brain slice methods. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 6.
A long-term effect of chronically implanted neural electrodes is the formation of a glial scar made up of reactive astrocytes, microglia and the matrix proteins they generate. Studies have shown glial fibrillary acidic protein (GFAP) and cytokines interleukin-1beta (IL-1β), tumor necrosis factor alpha (TNFα), and transforming growth factor beta 1 (TGFβ1) are involved with the initial and modulation phases of reactive astrogliosis. In the present study, nanopatterning of polydimethylsiloxane (PDMS) was attempted as a method for reducing the inflammatory response of glial cells. A unique feature of this study is the use of in vitro brain slice cultures (organotypic cultures) in order to more accurately depict the native response. The aim of the study was to determine whether nanotopography could reduce inflammatory signals typically resultant from neural electrode implantation. Specifically, observation of cell alignment and surveillance of GFAP, IL-1β, TNFα, and TGFβ1 gene expression around the PDMS pins was performed. Results of this study confirm nanopatterning not only influences cell morphology, but some of the molecular signals as well. These results collectively indicate nanopatterning improves the biocompatibility of PDMS by reducing inflammatory markers such as GFAP, IL-1β, TGFβ1 and TNFα compared to the non-patterned PDMS pins.
- A portable experimental apparatus for human olfactory fMRI experiments. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 6.
Human olfactory perception can be measured using psychophysical tools or more complex odor generating devices systems, namely olfactometers. The present paper is aimed at presenting a new inexpensive, non-voluminous portable olfactometer adapted for human fMRI experiments. The system adjusts odorant stimulus presentation to human nasal respiration and records behavioral responses in the same experimental device. Validation by psychophysical measures and photo-ionization detection showed a linear increase in both odor intensity perception and vapor concentration as a function of odorant concentration. Further validation by brain imaging revealed neural activation in typical olfactory areas. In summary, the system represents a new low-cost, easy-use, easy-maintenance portable olfactometry tool for brain imaging, opening up new possibilities for investigating neural response to odors using event-related fMRI designs.
- The cell injury device: A high-throughput platform for traumatic brain injury research. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 6.
A novel, automated system for delivering controlled scratch-induced trauma to brain cells cultured in multi-well plates was created and characterized. The system is equipped with high-throughput imaging and analysis capabilities, enabling quantitative measurements of cell migration. The scratch-area coefficient of variation of the device was between 3.9% and 8.4%, a significant improvement over traditional manual methods, which provided a scratch-area coefficient of variation of between 10.7% and 19.6%. The device's inexpensive imaging and analysis capabilities were comparable to a well-known system, the Discovery-1 (Molecular Devices), with no significant difference found between the two. When used for drug screening, the gap area of Neuro2a cells after 72h was significantly larger in samples containing UO126 (20μM), averaging 0.89mm(2)±0.21mm(2); compared with an average vehicle control gap area of 0.42mm(2)±0.1mm(2). A gradient response could also be detected among samples with increasing UO126 concentrations (0-20μM), due to decreased migration and/or proliferation of cells into the gap over the time period. Our device provides an inexpensive method for delivering a standardized, closely controlled pressure/scratch to brain cells cultured in multi-well plates. The system provides more consistent patterns of scratch-induced trauma to cultured cells when compared to traditional methods. This device is an effective platform for quantifying the injury response of cells, and has applications in testing the effectiveness of drugs on cell migration and proliferation which might potentially treat traumatic brain injury.
- A vibrotactile behavioral battery for investigating somatosensory processing in children and adults. [JOURNAL ARTICLE]
- J Neurosci Methods 2013 May 6.
The cortical dynamics of somatosensory processing can be investigated using vibrotactile psychophysics. It has been suggested that different vibrotactile paradigms target different cortical mechanisms, and a number of recent studies have established links between somatosensory cortical function and measurable aspects of behaviour. The relationship between cortical mechanisms and sensory function is particularly relevant with respect to developmental disorders in which altered inhibitory processing are postulated such as ASD and ADHD. In this study, a vibrotactile battery consisting of nine tasks (incorporating reaction time, detection threshold, amplitude- and frequency discrimination) is applied to a cohort of healthy adults and a cohort of typically developing children to assess the feasibility of such a vibrotactile battery in both cohorts, and compare performance between children and adults. The results show that children and adults are both able to perform these tasks with similar performance, although children are slightly less sensitive in frequency discrimination. Performance within different task-groups clusters together in adults, providing further evidence that these tasks tap into different cortical mechanisms, which is discussed. This clustering is not shown in children, possibly indicative of development and larger variability. In conclusion, in this study we show that both children and adults are able to perform an extensive vibrotactile battery and we show feasibility of applying this battery for application to other (e.g. neurodevelopmental) cohorts to probe different cortical mechanisms.