Do we have Independent Visual Streams for Perception and Action? a Response.

Schenk and McIntosh (2009) present the thesis that most visual behaviours, especially those of any significant complexity, are likely to involve collaboration between both visual streams. While very likely true, this statement does not contradict the perception-action model as proposed by Milner and Goodale (1995, 2006). The two visual system hypothesis implies two functionally specialized systems, and not, as Schenk and McIntosh propose, two behaviourally independent systems

Development of a measure of visuomotor control for assessing the long-term ef fects of concussion

Recently, researchers have found evidence that after a concussion, residual visuomotor control deficits may linger longer than working memory or psychomotor speed deficits. All of the major computer administered test batteries currently in use for concussion management rely on examination of the latter tasks, and lack any measure of visuomotor control. The present research set out to develop a task to measure visuomotor performance. Using a touch-screen computer, the task required participants to point towards or away from (i.e., antipointing) a target in a design simmilar to an anti-saccade task. The task required participants to use visual information to execute controlled movements, and is designed to measure movement planning, execution performance and accuracy. The task was delivered to a large sample of healthy individuals to develop a normative performance data set. A self-report questionnaire was used to identify a small group of individuals from the normative population who were identified with a prior history of concussion. These individuals were directly contrasted with the healthy individuals. While only a few reported moderate or severe concussions, and information about recency and number of occurrences was unavailable, performance differences were observed --providing evidence of residual deficits. In particular, while concussed individuals were not slower, or less accurate overall than the healthy population on the task, they demonstrated unusual hand and spatial asymmetries. Future research will compare recently concussed individuals with the normative set developed here, and will make direct comparisons with existing computer administered test batteries to determine the efficacy of visuomotor tasks for detecting the long-term effects of concussion

Perceptual and Memory Deficits in Unilateral Neglect

Unilateral neglect is a disorder in which patients behave as if the left half of space has ceased to exist. The disorder typically arises from right hemisphere brain damage involving the inferior parietal and superior temporal cortices. Classic models of neglect have suggested that the disorder represents impaired attentional functioning. More recently, research has suggested that the heterogeneous symptoms of neglect can not be fully explained by attentional deficits alone. This thesis first examined performance on both visual working memory and attention tasks in patients with right brain damage, some of whom presented with neglect. Results showed severe deficits in both domains. Next, prism adaptation, a treatment long understood to improve attention in neglect, was used to examine whether the technique could improve performance in domains not specifically related to attention. Results showed that prisms failed to meaningfully improve severe deficits in time perception and spatial working memory. Such deficits outside spatial attention may be the result of damage to perceptual systems. The final experimental chapter examined the potential for saccadic adaptation, an analogue of prism adaptation previously shown to induce some perceptual change, to influence both perception and action in ways relevant to neglect. Here, healthy individuals performed the classic saccadic adaptation paradigm, with performance on a line bisection and landmark task used as indices of action and perception respectively. The task was not found to measurably influence either domain. Overall, the thesis supports recent research that claims that neglect involves independent deficits, involving more than attention. Specifically, it provides evidence that working memory and perceptual deficits are not strongly coupled to spatial attention

A Method for Rearing Large Quantities of the Damselfly, Ischnura ramburii (Odonata: Coenagrionidae), in the Laboratory

Laboratory based experimental designs typically require large sample sizes of genetically related organisms at the same developmental stage. Several described methods for rearing damselflies have been published, but these methods require laborious techniques when rearing large quantities of damselflies simultaneously. We have developed a relatively easy and inexpensive method for rearing large quantities of a coenagrionid damselfly that streamlines previously published methods and employs new techniques that increase efficiency and yield. Culturing large numbers of damselflies in the laboratory is manageable and opens diverse research avenues

Thiolene-Based Microfluidic Flow Cells for Surface Plasmon Resonance Imaging

Thiolene-based microfluidic devices have been coupled with surface plasmon resonance imaging (SPRI) to provide an integrated platform to study interfacial interactions in both aqueous and organic solutions. In this work, we develop a photolithographic method that interfaces commercially available thiolene resin to gold and glass substrates to generate microfluidic channels with excellent adhesion that leave the underlying sensor surface free from contamination and readily available for surface modification through self-assembly. These devices can sustain high flow rates and have excellent solvent compatibility even with several organic solvents. To demonstrate the versatility of these devices, we have conducted nanomolar detection of streptavidin-biotin interactions using in situ SPRI. (C) 2011 American Institute of Physics. [doi:10.1063/1.3596395

Creating Complex Interfaces Using Surface-Initiated Polymerization and Post-Polymerization Modification

Presented at the Nano@Tech Meeting on November 8, 2016 at 12:00 p.m. in room 1117-1118 of the Marcus Nanotechnology Building, Georgia Tech.Jason Locklin obtained his BS from Millsaps College in 1999. He graduated with his MS from UAB in Chemistry in 2002 and PhD from the University of Houston in 2004 under the guidance of Rigoberto Advincula. Jason then served as a Director of Central Intelligence Postdoctoral Scholar at Stanford University in 2005 with Zhenan Bao in the Department of Chemical Engineering. In 2007, Locklin joined the University of Georgia in the Department of Chemistry and the College of Engineering and was promoted to Associate Professor in 2012. He has been awarded the Central Intelligence Agency Young Investigator Award (2007), NSF CAREER Award (2010), and the Northeast Georgia ACS Chemist of the Year for Research (2009-2010). His group is currently investigating surface initiated polymerization reactions, orthogonal self-assembly, reversible adhesives and hydrogels, antimicrobial surfaces for inert plastics, organic photovoltaic devices, and stimuli-responsive interfaces.Runtime: 56:37 minutesGenerating micro-and nanosized patterns on solid surfaces is an important area of research with relevance in many scientific and technological areas. In our recent approach to generate complex interfaces, we have developed a series of novel “click” and “click-like” reactions that can be used to selectively pattern different chemical functionality onto polymer brush supports using one pot, orthogonal chemical transformations. This talk will highlight surface initiated polymerization and post-polymerization modification of these polymer brush supports as a means to generate surfaces that can be used in a wide variety of applications, from reversible adhesives to antimicrobial coatings for inert plastics

Gregarine parasitism in dragonfly populations of Central Texas with an assessment of fitness costs in Erythemis simplicicollis.

Includes bibliographical references (p. ).Dragonfly parasites are widespread and frequently include gregarines (Phylum Apicomplexa) in the gut of the host. Gregarines are ubiquitous protozoan parasites that infect arthropods worldwide. More than 1,600 gregarine species have been described, but only a small percentage of invertebrates have been surveyed for these apicomplexan parasites. Some consider gregarines rather harmless, but recent studies suggest otherwise. Odonate-gregarine studies have more commonly involved damselflies, and some have considered gregarines to rarely infect dragonflies. In this study, dragonfly populations were surveyed for gregarines and an assessment of fitness costs was made in a common and widespread host species, Erythemis simplicicollis. Adult dragonfly populations were surveyed weekly at two reservoirs in close proximity to one another and at a flow-through wetland system. Gregarine prevalences and intensities were compared within host populations between genders, among locations, among wing loads, and through time. Host fitness parameters measured included wing load, egg size, clutch size, and total egg count. Of the 37 dragonfly species surveyed, 14 species (38%) hosted gregarines. Thirteen of those species were previously unreported as hosts. Gregarine prevalences ranged from 2% – 52%. Intensities ranged from 1 – 201. Parasites were aggregated among their hosts. Gregarines were found only in individuals exceeding a minimum wing load, indicating that gregarines are likely not transferred from the naiad to adult during emergence. Prevalence and intensity exhibited strong seasonality during both years at one of the reservoirs, but no seasonal trend was detected at the wetland. The seasonal trend at the reservoir suggests that gregarine oocyst viability parallels increasing host population densities and may be short-lived. Prevalence and intensity also differed between dragonfly populations at the locations. Regression analyses revealed that host species, host gender, month, and year were significant explanatory variables related to gregarine prevalence and intensity. The fitness parameters measured were not correlated with presence or intensity of gregarines, suggesting that either gregarines do not affect wing loading and egg production in E. simplicicollis, or that virulence depends on parasite intensity and/or the specific gregarine species infecting the hosts. Our results emphasize the importance of considering season, hosts, and habitat when studying gregarine-dragonfly ecology.by Jason L. Locklin.Ph.D

Self-Sorting Click Reactions That Generate Spatially Controlled Chemical Functionality on Surfaces

This Article describes the generation of a patterned surface that can be postpolymerization modified to incorporate fragile macromolecules or delicate biomolecules without the need for special equipment. Two monomers that undergo different click reactions, pentafluorophenyl acrylate (PFPA) and 4-(trimethylsilyl) ethynylstyrene (TMSES), were sequentially polymerized from a silicon surface in the presence of a shadowmask with UV light, generating 12.5 and 62 μm pitch patterns. Two different dyes, 1-aminomethylpyrene (AMP) and 5-azidofluorescein (AF), were covalently attached to the polymer brushes through aminolysis and dual desilylation/copper­(I)-catalyzed alkyne/azide cycloaddition (CuAAC) in one pot. Unlike most CuAAC reactions, the terminal alkyne of TMSES was not deprotected prior to functionalization. Although a 2 nm thickness increase was observed for poly­(PFPA) brushes after polymerization of TMSES, cross-contamination was not visible through fluorescence microscopy after functionalization

A Dynamic Duo: Pairing Click Chemistry and Postpolymerization Modification To Design Complex Surfaces

Advances in key 21st century technologies such as biosensors, biomedical implants, and organic light-emitting diodes rely heavily on our ability to imagine, design, and understand spatially complex interfaces. Polymer-based thin films provide many advantages in this regard, but the direct synthesis of polymers with incompatible functional groups is extremely difficult. Using postpolymerization modification in conjunction with click chemistry can circumvent this limitation and result in multicomponent surfaces that are otherwise unattainable. The two methods used to form polymer thin films include physisorption and chemisorption. Physisorbed polymers suffer from instability because of the weak intermolecular forces between the film and the substrate, which can lead to dewetting, delamination, desorption, or displacement. Covalent immobilization of polymers to surfaces through either a “grafting to” or “grafting from” approach provides thin films that are more robust and less prone to degradation. The grafting to technique consists of adsorbing a polymer containing at least one reactive group along the backbone to form a covalent bond with a complementary surface functionality. Grafting from involves polymerization directly from the surface, in which the polymer chains deviate from their native conformation in solution and stretch away from the surface because of the high density of chains. Postpolymerization modification (PPM) is a strategy used by our groups over the past several years to immobilize two or more different chemical functionalities onto substrates that contain covalently grafted polymer films. PPM exploits monomers with reactive pendant groups that are stable under the polymerization conditions but are readily modified via covalent attachment of the desired functionality. “Click-like” reactions are the most common type of reactions used for PPM because they are orthogonal, high-yielding, and rapid. Some of these reactions include thiol-based additions, activated ester coupling, azide–alkyne cycloadditions, some Diels–Alder reactions, and non-aldol carbonyl chemistry such as oxime, hydrazone, and amide formation. In this Account, we highlight our research combining PPM and click chemistry to generate complexity in polymer thin films. For the purpose of this Account, we define a complex coating as a polymer film grafted to a planar surface that acts as a template for the patterning of two or more discrete chemical functionalities using PPM. After a brief introduction to grafting, the rest of the review is arranged in terms of the sequence in which PPM is performed. First, we describe sequential functionalization using iterations of the same click-type reaction. Next, we discuss the use of two or more different click-like reactions performed consecutively, and we conclude with examples of self-sorting reactions involving orthogonal chemistries used for one-pot surface patterning