As neural interfaces continue to progress toward practical applications, there is increased demand for smaller, more efficient and cost effective devices. Event related potentials (ERPs) have recently been demonstrated to be reliable for practical communication in disabled individuals using the P300 Speller paradigm. With the objective of simplifying the processing of ERPs in order to minimize the hardware/computational requirements, and therefore the power consumption (for increased battery life for wireless, etc.), this study examines the effects of the analog-to-digital converter amplitude quantization on the ERP classification accuracy for the P300 Speller.

Non-invasive brain–computer interface (BCI) technology can restore communication for those unable to communicate due to loss of muscle control. Nonetheless, compared to augmentative and alternative communication (AAC) devices requiring muscular control, BCIs provide relatively slow communication. Therefore, implementing techniques improving BCI speed and accuracy is important. Previous studies indicate that facial stimuli elicit N170 and N400 components, in addition to the P300 component associated with P300 BCI. These additional components can increase speed and accuracy. Our study investigated the influence of image size and content using four conditions: large face, small face, large non-face, and small non-face. We predicted faces would provide higher accuracy than non-face stimuli and larger stimuli would provide higher accuracy than small stimuli. We found no significant difference in performance between conditions; however, significant waveform differences were found in each condition.

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Introduction Capillarity describes the effects caused by the surface tension on liquids. When considering small amounts ofliquid,thesurfacetension becomes the dominating parameter. In this situation the arising mathematical task is to determine the occurring capillary surface. At the beginning of the research on this topic, problems such as the ascent of fluids in a circular tube, on a vertical wall or on a wedge were some of the first problems scientists were concerned with. At the beginning of the 19th century, scientists like Young1, Laplace2, Taylor 3 and Gauß 4 established the mathematical foundations of this field. For the capillary tube5 they found, by applying variational methods, the so called mean curvature equation or capillary equation with the associated boundary condition. As Finn in [Fin86, Chapter 1] describes, this leads to the following boundary value problem: divTu = u + in , · Tu = cos on @ where Tu = ∇u p 1 + |∇u|2 . is called the Lagrange6 multiplier and is the contact angle, established between the capillary surface and the container wall. In the past, one tried to solve the problem by linearisation – with more or less satisfying results. In the last decades, expedited by the developing of micromechanics and the arising space-technology, capillary effects became more and more significant. Thereby the observed results differed from the predicted. The reason is the strong non-linearity of the problem. Interior molecular forces are responsible for the establishing of equilibrium surfaces. The force, operating between two materials, is called adhesion and cohesion is the molecular force within a medium. Under some specifications there arises a non-negligible force, called disjoining pressure. This pressure causes an additional term in the capillary equation, which 1Thomas Young (*13 June 1773, Milverton; †10 May 1829, London); Englisch polymath; made notable contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony and Egyptology, found the Young–Laplace equation 2Pierre-Simon (Marquis de) Laplace (28 March 1749, Beaumont-en-Auge; †5 March 1827, Paris); French mathematician and astronomer; found the Young–Laplace equation 3Brook Taylor (*18 August 1685, Edmonton; †29 December 1731, Somerset House/London); English mathematician; experiments in capillary attraction 4Johann Carl Friedlich Gauß (*30 April 1777, Braunschweig; †23 February 1855, G¨ottingen); German mathematician and scientist; contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics 5A capillary tube is a container with cross-section and perpendicular container walls, which contains an amount of liquid. 6Joseph-Louis de Lagrange (*25 January 1736, Turin; †10 April 1813, Paris); Italian mathematician and astronomer. 7 is called the disjoining pressure potential, denoted by P(x, u(x)). That is, we are led to the following modified capillary equation, see [MMS08]: divTu = u + P + in , with a similar boundary condition (see Section 1.3 for more details). The main task of this paper is to examine the behaviour of the capillary problem, considering the disturbance P. A generic example for such configurations is vapour nitrogen//liquid nitrogen//quartz, see also [Isr92, Chapter 11] or [MMS08]. The present work with regard to contents is divided in three parts. In the first part, inspired by the work of Concus and Finn [CF74], [FH89], we prove a Comparison Principle. As in the classical context, this principle is a powerful tool to find solutions of the boundary problem. Thus we can see that the disjoining pressure potential is the key for the asymptotic of the solutions. The second part is concerned with the asymptotic behaviour of the solutions for some classical cases. In particular for the capillary tube with circular cross-section (see [Mie93b], [Mie94], [Mie96] for the classical setting) the ascent on a horizontal wall and between two parallel horizontal plates, results are presented. There we are able to specify the asymptotic behaviour up to a constant term. In the last part we observe the solution of the problem on a corner. There it is more difficult to obtain a result. But in return, we gain a better result near the cusp of the edge. In the articles of Miersemann [Mie88], [Mie89], [Mie90] or Scholz [Sch04] some results for the classical setting are given. The formal arrangement is divided into three main chapters. The first of them is a summary of some notations which will be needed in the following chapters and also the physical background is illuminated. The main part, where asymptotic results are presented, is contained in Chapter 2. To afford a better reading, most of the proofs are given in Chapter 3.8

In order to further explore the nature of anesthesia-induced unconsciousness and its relationship to nociception, investigators attempted to determine whether mismatch negativity could be detected during general anesthesia and surgery. An auditory odd-ball paradigm designed to elicit mismatch negativity was presented to ten patients during general anesthesia and surgery. Five of the ten also underwent testing in the awake state prior to surgery. Multiple EEG recordings were obtained in each patient and each condition using the BioSemi ActiveTwo 64 EEG electrode system. The anesthetic regime required only that 0.7 MAC of an inhaled agent was administered. Several methods of analysis were utilized to determine whether an MMN response could be identified: visual inspection of ERP waveforms, targeted t-tests, cluster permutation tests, and multivariate pattern analysis. Whereas deviant-related negativity was readily detected in the awake state, deviant-related negativity was not detected during surgery and general anesthesia. Results demonstrate that essential components of the MMN response are abolished during typically conducted general anesthesia even with significant surgical stimulation. These results are consistent with previous research on ERPs and anesthesia. Results cast doubt on the possibility of sensory memory related to intraoperative events. / Thesis / Master of Science (MSc)

Brain-computer interface (BCI) technology holds promise to restore the communication and control ability of individuals with severe motor disabilities (Wolpaw et al. 2002). An EEG-based BCI system that detects the P300 event-related potential (ERP) allows users to select items from a matrix consisting of letters, numbers, and function calls (after the method of Donchin et al., 2000) using brain signals rather than the brain’s normal output pathways of peripheral nerves and muscles. Our laboratory seeks to realize independent home use of P300-based BCI by severely disabled individuals. In an earlier study, we found that P300-based BCI performance (i.e., accurate classification) on test data was correlated with the test data and was not correlated with the training data (Mak et al. 2009). The present study set out

<p>Cognitive impairments in schizophrenia (SZ) include abnormalities in executive function, attention, and semantic processing. Event-related potentials (ERPs) are used as neurophysiological measures of cognitive impairment that have been shown to map onto symptom dimensions of psychotic disorders, such as schizophrenia. While much research exists on schizophrenia, less is understood about the longitudinal relationships between ERPs and symptom dimensions among individuals at risk for psychosis. Of published work in risk samples, most have been cross-sectional, leaving clinical inferences regarding longitudinal patterns non-specific. The current study aimed to bridge this gap by recording ERPs (P300, ERN, N400) across a battery of tasks within a single risk sample, and measured positive, negative, and disorganized symptom severity via the Multidimensional Schizotypy Scale (MSS). Participants exhibiting psychosis-risk were recruited from the community (N=60), and completed a baseline and 6-month follow-up assessment (n=29). The primary goal of the baseline assessment aimed to replicate ERP-symptom dimension relationships observed in the SZ literature. Effect sizes for P300-positive and ERN-negative relationships were observed to be in the same directionality as noted in the clinical SZ literature. While not statistically significant, the small effects suggest that P300 and ERN may be similarly effected by presence of positive and negative symptoms, respectively. By contrast, N400, however, was found to have an effect size directionality opposite to that reported in the literature. This finding is consistent with mixed presentation of disorganized symptoms in clinical SZ populations. The follow-up assessment aimed to examine the relationship of symptom dimensions over time in a single at-risk sample, and leveraged ERPs as potential prospective predictors of worsening of symptoms. As expected, baseline symptoms prospectively predicted corresponding symptoms at follow-up. However, only N400 amplitude at baseline correlated with disorganized symptoms at follow-up, and no ERP prospectively predicted corresponding symptom dimensions at follow-up. Overall, examining the relationship between multiple ERPs and symptom dimensions in a single sample and via a longitudinal design is a novel addition to the literature. Future research will be necessary to clarify the use of ERPs as neural biomarkers to identify and predict symptom severity over time, ultimately reducing subjectivity in clinical diagnosis and treatment. </p>

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This study examined the effect of acute exercise on food motivation, energy intake, and total physical activity in normal-weight and obese women. Participants of both groups were matched (except for Body Mass Index) and conditions (exercise vs. non-exercise) were randomized and counter-balanced. Eighteen normal-weight and 17 obese women completed an exercise and non-exercise day, each performed on the same day of the week. Exercise was performed on a motor-driven treadmill at 3.8 mph and 0% grade for 45 continuous minutes. To test for food motivation, participants were shown a continuous stream of pictures of food and flowers (control) while neural activity was monitored. Data were analyzed using a 2-group x 2-exercise condition x 2-picture type repeated measures analysis of covariance on event-related potential (ERP) amplitude and latency. Dietary records were analyzed using the Food Processor SQL nutrition software. Physical activity was monitored using a GT1M accelerometer. For both groups under both conditions, ERP amplitude was higher and latency was lower for food pictures compared to flower pictures. When normal-weight and obese women were combined, there was a significant condition*picture type interaction for late positive potential (P=0.04) with participants showing less neurological response to food pictures following a 45-minute exercise bout. Exercise did not alter energy intake. However, the exercise condition resulted in significantly more total physical activity, moderate intensity, vigorous intensity, moderate-to-vigorous (MVPA) intensity activity, and less sedentary time than the non-exercise condition. There was a significant group*condition interaction for MVPA (P=0.043) with obese women showing less MVPA than the normal-weight group. The sample of women studied did not show neurological differences in response to pictures of food based upon BMI. However, exercise decreased neurological responses to food, which may indicate lower food motivation. A supervised and planned exercise bout dramatically increased total physical activity in normal-weight and obese women compared to a day without planned exercise. There may be some negative compensation for MVPA in obese women following a 45-minute exercise bout compared to normal-weight women.