Visualization Techniques for the Analysis of Neurophysiological Data

In order to understand the diverse and complex functions of the Human brain, the temporal relationships of vast quantities of multi-dimensional spike train data must be analysed. A number of statistical methods already exist to analyse these relationships. However, as a result of expansions in recording capability hundreds of spike trains must now be analysed simultaneously. In addition to the requirements for new statistical analysis methods, the need for more efficient data representation is paramount. The computer science field of Information Visualization is specifically aimed at producing effective representations of large and complex datasets. This thesis is based on the assumption that data analysis can be significantly improved by the application of Information Visualization principles and techniques. This thesis discusses the discipline of Information Visualization, within the wider context of visualization. It also presents some introductory neurophysiology focusing on the analysis of multidimensional spike train data and software currently available to support this problem. Following this, the Toolbox developed to support the analysis of these datasets is presented. Subsequently, three case studies using the Toolbox are described. The first case study was conducted on a known dataset in order to gain experience of using these methods. The second and third case studies were conducted on blind datasets and both of these yielded compelling results

Neural hypersensitivity to pleasant touch in women remitted from anorexia nervosa.

Interoception, or the sensing and integration of bodily state signals, has been implicated in anorexia nervosa (AN), given that the hallmark symptoms involve food restriction and body image disturbance. Here we focus on brain response to the anticipation and experience of affective interoceptive stimuli. Women remitted from AN (RAN; N = 18) and healthy comparison women (CW; N = 26) underwent a pleasant affective touch paradigm consisting of gentle strokes with a soft brush administered to the forearm or palm during functional neuroimaging. RAN had a lower brain response relative to CW during anticipation of touch, but a greater response when experiencing touch in the right ventral mid-insula. In RAN, this reduced anticipatory response was associated with higher levels of harm avoidance. Exploratory analyses in RAN also suggested that lower response during touch anticipation was associated with greater body dissatisfaction and higher perceived touch intensity ratings. This reduced responsivity to the anticipation of pleasant affective interoceptive stimuli in association with higher harm avoidance, along with an elevated response to the experience of touch, suggests an impaired ability in AN to predict and interpret incoming physiological stimuli. Impaired interoception may thus impact one's sense of self, thereby supporting observations of disturbed body image and avoidance of affective and social stimuli. Therapeutic approaches that help AN to better anticipate and interpret salient affective stimuli or improve tolerance of interoceptive experiences may be an important addition to current interventions

The value of [18F]FDG-PET in the diagnosis of large-vessel vasculitis and the assessment of activity and extent of disease

Purpose: This study was performed to investigate the value of 18F-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) in the diagnosis of large-vessel vasculitis and the assessment of activity and extent of disease. Methods: Twenty-six consecutive patients (21 females, 5 males; median age -years, range 17-86years) with giant cell arteritis or Takayasu's arteritis were examined with [18F]FDG-PET. Follow-up scans were performed in four patients. Twenty-six age- and gender-matched controls (21 females, 5 males; median age 71years, range 17-86years) were included. The severity of large-vessel [18F]FDG uptake was visually graded using a four-point scale. C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) were measured and correlated with [18F]FDG-PET results by logistic regression. Results: [18F]FDG-PET revealed pathological findings in 18 of 26 patients. Three scans were categorised as grade I, 12 as grade II and 3 as grade III arteritis. Visual grade was significantly correlated with both CRP and ESR levels (p=0.002 and 0.007 respectively; grade I: CRP 4.0mg/l, ESR 6mm/h; grade II: CRP 37mg/l, ESR 46mm/h; grade III: CRP 172mg/l, ESR 90mm/h). Overall sensitivity was 60% (95% CI 40.6-77.3%), specificity 99.8% (95% CI 89.1-100%), positive predictive value 99.7% (95% CI 77-100%), negative predictive value 67.9% (95% CI 49.8-80.9%) and accuracy 78.6% (95% CI 65.6-88.4%). In patients presenting with a CRP <12mg/l or an ESR <12mm/h, logistic regression revealed a sensitivity of less than 50%. In patients with high CRP/ESR levels, sensitivity was 95.5%/80.7%. Conclusion: [18F]FDG-PET is highly effective in assessing the activity and the extent of large-vessel vasculitis. Visual grading was validated as representing the severity of inflammation. Its use is simple and provides high specificity, while high sensitivity is achieved by scanning in the state of active inflammatio

A Deep Photometric Look at Two of Andromeda's Dwarf Spheroidals: X and XVII

We use deep wide-field photometry from the Large Binocular Camera to study the stellar and structural properties of the recently discovered Andromeda X and Andromeda XVII (And X and And XVII) dwarf galaxies. Using the mean apparent magnitude of the horizontal branch (HB), we derive distances of 621 +- 20 kpc to And X and 734+- 23 kpc to And XVII, closer by >60 kpc than the previous estimates which were based on red giant branch (RGB) observations. Thus our results warrant against the use of the RGB tip method for determining distances to systems with sparsely populated RGBs, and show how crucial HB observations are in obtaining accurate distances in systems such as these. We find that And X is a relatively faint (MV = -7.36), highly elongated (e = 0.48) system at a distance of 174 +- 62 kpc from Andromeda. And XVII is brighter (MV = -8.61) with an M31-centric distance of 73 kpc which makes it one of the closest satellites to Andromeda. Both galaxies are metal-poor: we derive =-2.2 for And X, while And XVII shows = -2.0, consistent with the relation of higher luminosity dwarfs being more metal- rich. Additionally, both galaxies show considerable intrinsic spreads in metallicity (0.2 and 0.3 dex for And X and And XVII respectively), consistent with multiple stellar populations.Comment: 8 pages, 6 figure

1.6 W continuous-wave Raman laser using low-loss synthetic diamond

Low-birefringence (Δn<2x10−6), low-loss (absorption coefficient <0.006cm−1 at 1064nm), single-crystal, synthetic diamond has been exploited in a CW Raman laser. The diamond Raman laser was intracavity pumped within a Nd:YVO4 laser. At the Raman laser wavelength of 1240nm, CW output powers of 1.6W and a slope efficiency with respect to the absorbed diode-laser pump power (at 808nm) of ~18% were measured. In quasi-CW operation, maximum on-time output powers of 2.8W (slope efficiency ~24%) were observed, resulting in an absorbed diode-laser pump power to the Raman laser output power conversion efficiency of 13%

Continuous-wave Raman laser pumped within a semiconductor disk laser cavity

A KGd(WO4)(2) Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5: 6W of absorbed diode pump power, and output power up to 0.8W at 1143nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157nm

Multiband Wavelet Age Modeling for a ∼293 m (∼600 kyr) Sediment Core From Chew Bahir Basin, Southern Ethiopian Rift

The use of cyclostratigraphy to reconstruct the timing of deposition of lacustrine deposits requires sophisticated tuning techniques that can accommodate continuous long-term changes in sedimentation rates. However, most tuning methods use stationary filters that are unable to take into account such long-term variations in accumulation rates. To overcome this problem we present herein a new multiband wavelet age modeling (MUBAWA) technique that is particularly suitable for such situations and demonstrate its use on a 293 m composite core from the Chew Bahir basin, southern Ethiopian rift. In contrast to traditional tuning methods, which use a single, defined bandpass filter, the new method uses an adaptive bandpass filter that adapts to changes in continuous spatial frequency evolution paths in a wavelet power spectrum, within which the wavelength varies considerably along the length of the core due to continuous changes in long-term sedimentation rates. We first applied the MUBAWA technique to a synthetic data set before then using it to establish an age model for the approximately 293 m long composite core from the Chew Bahir basin. For this we used the 2nd principal component of color reflectance values from the sediment, which showed distinct cycles with wavelengths of 10–15 and of ∼40 m that were probably a result of the influence of orbital cycles. We used six independent 40Ar/39Ar ages from volcanic ash layers within the core to determine an approximate spatial frequency range for the orbital signal. Our results demonstrate that the new wavelet-based age modeling technique can significantly increase the accuracy of tuned age models

The impact of 18F-FDG PET on the management of patients with suspected large vessel vasculitis

Purpose: We aimed to assess the impact of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) on the management of patients with suspected large vessel vasculitis. Methods: An international expert panel determined diagnoses and clinical management in patients with suspected large vessel vasculitis, with and without the results of 18F-FDG PET, respectively. The accuracy of the clinical diagnosis and the resulting clinical management with and without the 18F-FDG PET results were compared using logistic regression models. Results: The analysis included 30 patients referred to a tertiary care centre with large vessel vasculitis and 31 controls. 18F-FDG PET had an overall sensitivity of 73.3% [95% confidence interval (CI) 54.1-87.7%], a specificity of 83.9% (95% CI 66.3-94.5%), a positive predictive value of 81.5% (95% CI 61.9-93.7%) and a negative predictive value of 76.5% (95% CI 58.8-89.3%). The diagnostic accuracy of 18F-FDG PET was higher in patients not receiving immunosuppressive drugs (93.3 vs 64.5%, p = 0.006). Taken in context with other available diagnostic modalities, the addition of 18F-FDG PET increased the clinical diagnostic accuracy from 54.1 to 70.5% (p = 0.04). The addition of 18F-FDG PET increased the number of indicated biopsies from 22 of 61 patients (36.1%) to 25 of 61 patients (41.0%) and changed the treatment recommendation in 8 of 30 patients (26.7%) not receiving immunosuppressive medication and in 7 of 31 patients (22.6%) receiving immunosuppressive medication. Conclusion: 18F-FDG PET is a sensitive and specific imaging tool for large vessel vasculitis, especially when performed in patients not receiving immunosuppressive drugs. It increases the overall diagnostic accuracy and has an impact on the clinical management in a significant proportion of patient

Sustained efficacy, safety and patient-reported outcomes of certolizumab pegol in axial spondyloarthritis: 4-year outcomes from RAPID-axSpA.

Objective: The aim was to assess the long-term safety and efficacy of certolizumab pegol over 4 years of continuous treatment in patients with axial spondyloarthritis (axSpA), including both AS and non-radiographic (nr-) axSpA. Methods: RAPID-axSpA was a phase 3 randomized trial, double blind and placebo controlled to week 24, dose blind to week 48 and open label to week 204. Patients had a clinical diagnosis of axSpA, meeting Assessment of SpondyloArthritis international Society (ASAS) criteria, and had active disease. The assessed outcomes included ASAS20, ASAS40, AS DAS (ASDAS), BASDAI, BASFI and BASMI scores, along with selected measures of remission. Further patient-reported outcomes, peripheral arthritis, enthesitis, uveitis and quality-of-life measures are also reported. Results: Two hundred and eighteen of 325 patients randomized (AS: 121; nr-axSpA: 97) received certolizumab pegol from week 0. Of these, 65% remained in the study at week 204 (AS: 67%; nr-axSpA: 63%). Across all outcomes, for AS and nr-axSpA, sustained improvements were observed to week 204 [week 204 overall axSpA: ASAS20: 54.1% (non-responder imputation); 83.7% (observed case, OC); ASAS40: 44.0% (non-responder imputation); 68.1% (OC); ASDAS inactive disease: 32.1% (last observation carried forward); 31.4% (OC)]. In the safety set (n = 315), there were 292.8 adverse events and 10.4 serious adverse events per 100 patient-years. No deaths were reported. Conclusion: In the first study to evaluate the efficacy of an anti-TNF across both axSpA subpopulations, improvements in clinical and patient-reported outcomes at 24 and 96 weeks were sustained through 4 years of treatment, with no new safety signals. Trial registration: ClinicalTrials.gov, http://clinicaltrials.gov, NCT01087762

Sucrose activates human taste pathways differently from artificial sweetener

Animal models suggest that sucrose activates taste afferents differently than non-caloric sweeteners. Little information exists how artificial sweeteners engage central taste pathways in the human brain. We assessed sucrose and sucralose taste pleasantness across a concentration gradient in 12 healthy control women and applied 10% sucrose and matched sucralose during functional magnet resonance imaging. The results indicate that (1) both sucrose and sucralose activate functionally connected primary taste pathways; (2) taste pleasantness predicts left insula response; (3) sucrose elicits a stronger brain response in the anterior insula, frontal operculum, striatum and anterior cingulate, compared to sucralose; (4) only sucrose, but not sucralose, stimulation engages dopaminergic midbrain areas in relation to the behavioral pleasantness response. Thus, brain response distinguishes the caloric from the non-caloric sweetener, although the conscious mind could not. This could have important implications on how effective artificial sweeteners are in their ability to substitute sugar intake