Current Trends of fMRI in Vision Science: A Review

Studying brain functional activities is an area that is experiencing rapid interest in the field of neuroimaging. Functional magnetic resonance imaging (fMRI) has provided vision science researchers a powerful and noninvasive tool to understand eye function and correlate it with brain activities. In this chapter, we focus on the physiological aspects followed by a literature review. More specifically, to motivate and appreciate the complexity of the visual system, we will begin with a description of specific stages the visual pathway, beginning from the distal stimulus and ending in the visual cortex. More importantly, the development of ascending visual pathway will be discussed in order to help in understanding various disorders associated with it such as monochromacy, albinism, amblyopia (refractive, strabismic). In doing so we will divide the first half into two main sections, the visual pathway and the development of the ascending pathway. The first of these sections will be mostly an anatomy review and the latter will discuss the development of this anatomy with specific examples of disorders as a result of abnormal development. We will then discuss fMRI studies with focus on vision science applications. The remaining sections of this chapter will be highlighting the work done on mainly oculomotor function, some perception and visual dysfunction with fMRI and investigate the differences and similarities in their findings. We will then conclude with a discussion on how this relates to neurologists, neuroscientists, ophthalmologists and other specialists

New Window on Optical Brain Imaging; Medical Development, Simulations and Applications

In this chapter we hope to give a technological review of near-infrared light and systems, discuss optode design considerations including background on the fiber design as it relates to this field and finally touch on current trends and applications. For the latter, we will focus on diffusion theory and simulation of photon propagation using a head model. We will follow this with concluding remarks

Evaluation of Interpolation Effects on Upsampling and Accuracy of Cost Functions-Based Optimized Automatic Image Registration

Interpolation has become a default operation in image processing and medical imaging and is one of the important factors in the success of an intensity-based registration method. Interpolation is needed if the fractional unit of motion is not matched and located on the high resolution (HR) grid. The purpose of this work is to present a systematic evaluation of eight standard interpolation techniques (trilinear, nearest neighbor, cubic Lagrangian, quintic Lagrangian, hepatic Lagrangian, windowed Sinc, B-spline 3rd order, and B-spline 4th order) and to compare the effect of cost functions (least squares (LS), normalized mutual information (NMI), normalized cross correlation (NCC), and correlation ratio (CR)) for optimized automatic image registration (OAIR) on 3D spoiled gradient recalled (SPGR) magnetic resonance images (MRI) of the brain acquired using a 3T GE MR scanner. Subsampling was performed in the axial, sagittal, and coronal directions to emulate three low resolution datasets. Afterwards, the low resolution datasets were upsampled using different interpolation methods, and they were then compared to the high resolution data. The mean squared error, peak signal to noise, joint entropy, and cost functions were computed for quantitative assessment of the method. Magnetic resonance image scans and joint histogram were used for qualitative assessment of the method

Stimulus and Optode Placement Effects on Functional Near-Infrared Spectroscopy of Visual Cortex

Functional near-infrared spectroscopy has yet to be implemented as a stand-alone technique within an ophthalmology clinical setting, despite its promising advantages. The present study aims to further investigate reliability of visual cortical signals. This was achieved by: (1) assessing the effects of optode placements using the 10–20 International System of Electrode Placement consisting of 28 channels, (2) determining effects of stimulus size on response, and (3) evaluating response variability as a result of cap placement across three sessions. Ten participants with mean age 23.8 4.8 years (five male) and varying types of hair color and thickness were recruited. Visual stimuli of black-and-white checkerboards, reversing at a frequency of 7.5 Hz were presented. Visual angles of individual checker squares included 1 deg, 2 deg, 5 deg, 9 deg, and 18 deg. The number of channels that showed response was analyzed for each participant, stimulus size, and session. 1-deg stimulus showed the greatest activation. One of three data collection sessions for each participant gave different results (p \u3c 0.05). Hair color and thickness each had an effect upon the overall HbO (p \u3c 0.05), while only color had a significant effect for HbD (p \u3c 0.05). A reliable level of robustness and consistency is still required for clinical implementation and assessment of visual dysfunction

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Current Trends of fMRI in Vision Science: A Review

Studying brain functional activities is an area that is experiencing rapid interest in the field of neuroimaging. Functional magnetic resonance imaging (fMRI) has provided vision science researchers a powerful and noninvasive tool to understand eye function and correlate it with brain activities. In this chapter, we focus on the physiological aspects followed by a literature review. More specifically, to motivate and appreciate the complexity of the visual system, we will begin with a description of specific stages the visual pathway, beginning from the distal stimulus and ending in the visual cortex. More importantly, the development of ascending visual pathway will be discussed in order to help in understanding various disorders associated with it such as monochromacy, albinism, amblyopia (refractive, strabismic). In doing so we will divide the first half into two main sections, the visual pathway and the development of the ascending pathway. The first of these sections will be mostly an anatomy review and the latter will discuss the development of this anatomy with specific examples of disorders as a result of abnormal development. We will then discuss fMRI studies with focus on vision science applications. The remaining sections of this chapter will be highlighting the work done on mainly oculomotor function, some perception and visual dysfunction with fMRI and investigate the differences and similarities in their findings. We will then conclude with a discussion on how this relates to neurologists, neuroscientists, ophthalmologists and other specialists

White Matter Analysis of Idiopathic Nystagmus Syndrome

Idiopathic Nystagmus Syndrome (INS) is characterized by an early onset alternating series of slow and rapid eye movements which can manifest in different waveforms and genetic lines. The cause of INS is not known, however ocular motor function is known to involve the brainstem and cerebellum. The purpose of this study was to investigate white matter structure in the brainstem between INS patients and normal controls

Interpolation-Based Super-Resolution Reconstruction: Effects of Slice Thickness

Standard clinical magnetic resonance imaging (MRI) is acquired in two-dimensions where the in-plane resolution is higher than the slice select direction. These acquisitions include axial, coronal, and sagittal planes. To date, there have been few attempts to combine the information of these three orthogonal orientations. This paper aims to take advantage of the different in-plane resolution acquired from each plane orientation and combine them into one volume in order to attain a higher resolution image. This combination of MRI data will allow the detection of smaller areas that would otherwise be missed using only one slice orientation. A comparison of slice thicknesses along with image registration is performed. The mean-squared error and peak signal-to-noise were computed for quantitative assessment. MRI and phantom scans and joint histograms were used for qualitative assessment

White Matter Analysis of Idiopathic Nystagmus Syndrome

Idiopathic Nystagmus Syndrome (INS) is characterized by an early onset alternating series of slow and rapid eye movements which can manifest in different waveforms and genetic lines. The cause of INS is not known, however ocular motor function is known to involve the brainstem and cerebellum. The purpose of this study was to investigate white matter structure in the brainstem between INS patients and normal controls

A Practical Guide to an fMRI Experiment

Functional Magnetic Resonance Imaging (fMRI) has been around for two decades and research in this field has been exponentially rising. Much of this research has been dominated by basic science. Recent trends have brought the clinical realm into play in which valuable contributions can still be made. Helping the clinician understand the basic concepts behind an fMRI experiment is crucial to further developing and evaluating functional paradigms and research. Critical to designing an fMRI experiment is understanding the related physics and how fine tuning scanning parameters affects the image quality, which in turn affect the findings of an fMRI study. In addition, understanding the physiology behind the acquired signal and anatomy of the brain is also important. To appreciate the complexity of the fMRI process see (Amaro & Barker, 2006; Savoy, 2005). In this chapter we present a practical guide to the novice on the important aspects needed to perform an efficient fMRI experiment from idea formulation to understanding the possible limitations of the results. The basic concepts of fMRI, beginning with image resolution and physics, will be discussed along with advice on possible pearls and pitfalls of this process. Points covered will include: paradigm design, scanning protocol, and limitations