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This paper presents the alteration of P300 and N2b during the auditory oddball protocol prior to and following theta-burst stimulation (TBS) over left prefrontal cortex in schizophrenia. Effects of repetitive continuous TBS (cTBS) on selective attention cognitive process were investigated by Event-related potentials (ERPs) in 10 subjects with schizophrenia. TBS trains were delivered over the left...
Using a novel, fully-mobile virtual reality paradigm, we investigated the EEG correlates of spatial representations formed during unsupervised exploration. During a test phase, 24-hours after initial exploration, when subjects perceived an object that was incongruent with their spatial expectations we found a decreased negativity peaking at 170ms with scalp topography consistent with generation in...
In models of electrical stimulation of the retina, somata are typically represented either as several compartments or just a single compartment. When stimulated by a subretinal or suprachoroidal prosthesis, the soma polarizes within a microsecond after the application of extracellular field, whereas neurites polarize at a slower rate. We describe an idealized model that compares these two mechanisms...
The relative position of an indwelling electrode to the nerve fiber plays a critical role in the shape of the single fiber action potential (SFAP) detected by the electrode. Parameters such as electrode to fiber distance, fiber path, and position of the nodes of Ranvier can have a substantial influence on the shape and frequency content of the SFAP. This study explores the effects of these parameters...
Transcranial magnetic stimulation (TMS) of the dorsolateral prefrontal cortex (DLPFC) is increasingly used as a non-invasive treatment for medication-resistant depression. However, this target site is commonly localized using an inaccurate standard procedure, which uses a fixed distance with respect to the motor cortical site for optimal stimulation of a hand muscle. Several studies have suggested...
The quantification of Magnetic Resonance Spectroscopy (MRS) signal remains challenging due to the low signal-to-noise ratio (SNR) of data. All time-domain quantification methods highly require user interactions, which reduce the reproducibility of the data quantification. The goal of our work is to design a systematic methodology for automated quantification of a weak signal in MRS data. We used Hankel...
Noninvasive electroencephalographic (EEG) recordings have been successfully used to study motor-related brain activity in humans. We recently used an instruction delay paradigm to investigate the EEG signatures associated with preparation, planning and execution of arm isometric exertions. Subjects (n=8), prepared, planned and exerted force with their right arm in horizontal plane, according to visual...
A general model-based methodology is presented for the optimal design of stimulation patterns in the CA1 region of the hippocampus of non-human primates (NHP) that seeks to enhance performance in a Delayed-Match-to-Sample task. The methodology follows a hierarchical Volterra-type modeling approach that expresses the probability of a correct behavioral outcome in terms of multi-convolutional modules...
In this paper we present a linear dynamical system to model the ongoing neural response, measured by EEG, while a listener is selectively attending a speech stream that is presented in a mixture. In our state-space formulation, the latent state variables represent the activity of the underlying neural substrates and the ongoing neural dynamics are captured by a multivariate autoregressive model with...
Working memory (WM) refers to the short-term maintenance of information with higher cognitive functions. Recent researches show that local field potentials (LFPs) and spikes as different modes of neural signals encode WM respectively. There is a growing interest in how these two signals encode WM in coordination. The aim of this study is to investigate spike-LFP coupling coding WM via joint entropy...
A new method of detecting somatosensory evoked potentials (SSEP) is proposed using a time-frequency based windowing to enhance the signal to noise ratio (SNR) of the recorded SSEP signals. A sequential computation of maxima and minima was then used to find the location of characteristic positive and negative peaks of the SSEP. The algorithm rejects trials with high peak value as they are corrupted...
Deep brain stimulation (DBS) leads with radially-segmented contacts are an enabling technology to more precisely sculpt neuronal activation and potentially improve clinical outcomes for patients with a number of brain disorders. In this study, we developed a computational modeling approach to investigate the relationship between the number of radial contacts around a DBS lead and the degree to which...
Despite the growing scientific evidence that supports the efficacy of deep brain stimulation (DBS) for controlling epileptic seizure dynamics, further research remains mandatory to optimize DBS parameters for an efficient clinical use. In particular, progress can be expected from detailed study of the still poorly understood mechanisms that are responsible for the modulation of neural activity by...
A multi-compartmental molecular model has been developed for rodent basal forebrain cholinergic neurons with established gene expression levels. Reconstruction of neurons and network function were acquired using the Transcriptome-To-Physiome™ (TTP™) NeurobioSimulation. Gene expression values [NCBI GEO GSE 13379] were used to derive protein level and kinetic parameters for ligand and voltage gated...
Deep brain stimulation (DBS) alleviates the symptoms of some neurological disorders by stimulating specific neural targets. If electrodes are placed off target, DBS amplitude must be decreased to avoid side effects induced by stimulating other neural regions. We present a novel electrode geometry capable of radial charge steering. Computational modeling results show that radial charge steering will...
A patient-specific modelling technique for simulation of the electric field surrounding deep brain stimulation (DBS) electrodes has been adapted to T1 and T2-weigthed, proton density (PrD) and spoiled gradient echo (SPGR) magnetic resonance imaging (MRI) sequences. Electrical conductivity (σ) assignment of gray and white matter was made dependent on the neuromodulator settings. Nine brain models with...
Brain-machine interfaces (BMIs) are increasingly being used in rehabilitation research to improve the quality of life of clinical populations. Current BMI technology allows us to control, with a high level of accuracy, the positioning of robotic hands in space. We have shown previously that it is possible to decode the dexterous movements of fingers during grasping, from noninvasively recorded electroencephalographic...
This paper reports on a study in which a novel virtual moving sound-based spatial auditory brain-computer interface (BCI) paradigm is developed. Classic auditory BCIs rely on spatially static stimuli, which are often boring and difficult to perceive when subjects have non-uniform spatial hearing perception characteristics. The concept of moving sound proposed and tested in the paper allows for the...
This paper introduced a method for biometric authentication using EEG signals. Especially, we focused on the performance of reproducibility for personal authentication. Four healthy subjects participated in the experiment. EEG was measured from only one bipolar channel (O1A2) during resting state with closed eyes. EEG was also recorded with same protocol from same subjects on different days to verify...
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