Main Concept Production in Persons with Aphasia: A Comparison of Subtypes

Narrative abilities are negatively impacted in persons with aphasia (PWAs), with even the mildest PWAs producing narratives that, though well-structured, are characterized by reduced lexical diversity, complexity, content, length, coherence, and more (e.g., Andreetta, Cantagallo, & Marini, 2012; Capilouto, Wright, and Wagovich, 2006; Fergadiotis & Wright, 2011; Nicholas & Brookshire, 1995; Ulatowska, North, & Macaluso-Haynes, 1981). Even those categorized as “not aphasic by WAB” (NABW) produce significantly different story retell narratives compared to typical and aphasic peers (Author2, Dillow, & Author1, 2013). Diminished narrative abilities, and associated reduced functional communication, have a marked negative impact on quality of life (QoL) in PWAs, more so than physical limitations that accompany stroke (Hilari, 2011; Northcott & Hilari, 2011). Indeed, narrative ability may be a better predictor of life participation and QoL than traditionally administered outcome measures (Ross & Wertz, 1999), making imperative the advancement of narrative assessment and treatment. Three primary barriers to narrative assessment impede widespread use - standardization, norm-reference, and time constraints. AphasiaBank developers (http://talkbank.org/AphasiaBank/) addressed the first barrier by making available a standard discourse protocol. Regarding the second barrier, norm-referenced Main Concept (MC) lists based on 150+ control transcripts for three different types of discourse were recently developed using AphasiaBank (Author2, Campbell, Williams, Dillow, & Author1, 2013). The MC lists included concepts spoken by 50% of the control population. The authors elected to develop MC lists primarily because 1) MC analysis is a reliable and valid method of assessing narrative adequacy in PWAs (Nicholas & Brookshire, 1995), and 2) generation of standardized, norm-referenced, non-transcription-based MC lists would reduce the amount of time required for narrative assessment (third barrier). Previous MC research has revealed differences between controls and PWAs, and between fluent and non-fluent PWAs (Kong, 2009, 2011; Nicholas & Brookshire, 1995). Previous MC studies have also combined certain codes (see Discussion), which may lead to inaccurate representation of communicative abilities and/or masking of differences between subtypes. We extracted lengthy narrative samples of a large group of PWAs and analyzed the samples with a multi-level MC coding system using norm-referenced MCs in order to determine 1) if there were significant differences in MC production between different aphasia subtypes, and 2) if so, which subtypes were significantly different from each othe

Core Lexicon and Main Concept Production during Picture Description

Discourse is a highly complex and individualized communication act wherein individuals not only transmit and receive information for survival and cooperation, but also use spoken language for ritual purposes (e.g., relationships, fellowship, co-participation; Carey, 1988; Dimbleby & Burton, 1998). Discourse in typical and clinical populations has been investigated with a variety of structuralist, functionalist, and hybrid techniques (see Armstrong, 2000), and is known to be a good predictor of quality of life and life participation in persons with aphasia (PWAs). Discourse analysis, however, generally requires specialized training and can be time-consuming. MacWhinney, Fromm Holland, Forbes, & Wright (2010) suggested that analysis of a core lexicon during structured narrative tasks could provide a time-efficient and informative index of functional communication abilities. For example, clinicians could bypass lengthy transcriptions, instead generating a list of words spoken during narration for later comparison to a core lexicon (CoreLex). Using various methods, CoreLex has so far been investigated for the Cinderella story, a monologic story retell narrative task (Author1, Dillow, & Author2, 2013; MacWhinney et al., 2010) and a procedural narrative task where patients describe how to make a PB&J sandwich (Fromm, Forbes, Holland, & MacWhinney, 2013). CoreLex performance is strongly correlated with main concept (MC) production, a measure of narrative adequacy, during Cinderella retelling (Author1, Dillow, & Author2, 2013). Similar investigations for other narrative tasks are needed. The aims of this study were to 1) determine the CoreLex of a picture sequence description task included in the AphasiaBank protocol (Breaking Window), 2) calculate a CoreLex score for controls and PWAs, and 3) determine how well CoreLex predicts narrative adequacy, as judged by MC analysis

Story Grammar Analysis in Persons with Mild Aphasia

Narratives are often the basis of daily conversational interactions. When narrative skills are compromised, functional conversation is negatively impacted. Narrative coherence can be impacted even in clinical populations with mild word-finding deficits, such as anomic aphasia (Andreetta, Cantagallo, & Marini, 2012). The narrative abilities of those individuals who have had a stroke (and perhaps a previous aphasia diagnosis) but who perform within the normal range on standardized aphasia assessment measures have not been characterized. As every clinician/clinical researcher knows, this subgroup still includes individuals who have difficulty in conversation, who cannot return to work, and whose life participation is negatively impacted. Using AphasiaBank categorization (as this study relies on AphasiaBank transcripts), we refer to this subgroup as “not aphasic by WAB” (NABW). In both persons with anomic aphasia (PWaAs) and NABWs, deficits may be so minor that they are not apparent on traditional standardized assessment measures, but it should not be assumed that they do not exist and do not affect functional communication abilities. Unfortunately, there is often very little help to be offered for this population. In order to continue progressive development of interventions for PWaAs and NABWs, more information regarding narrative strengths and weaknesses in this population is needed. Story grammar analysis is a well-known method of analyzing narrative discourse in several clinical populations and is likely to be sensitive to differences between closely matched groups. The specific aims of this study are to 1) determine if there are differences between PWaAs, NABW, and non-brain injured controls (NBIs) on production of story grammar components during retelling of the Cinderella story, and 2) to examine the relationship between story grammar measures and an easily and quickly derived discourse measure called CoreLex to further characterize the relationship between micro- and macro-level processes in persons with mild aphasia

Short-range order in ferroelectric triglycine sulphate

he short-range order in triglycine sulphate (TGS) was investigated using x-ray and neutron di raction techniques. Complete deuteration of TGS was required for the neutron di raction experiments and a new method was developed to grow single crystals of fully deuterated TGS by vapour di usion crystallisation. The long-range structure of fully deuterated TGS was re ned at several temperatures from single crystal neutron di raction data and found to be consistent with the published structure of hydrogenous TGS. The phase transition temperature was found to increase from about 322 K to about 334 K with complete deuteration. The evolution of the long-range structure with temperature was investigated using x-ray and neutron powder di raction. All of the lattice parameters had a single cusp at the phase transition, except for the b lattice parameter, which also had a second cusp about 34 K below TC. In contrast to the lattice parameter behaviour, the unit cell volume was found to increase monotonically with temperature. The length of the hydrogen bonds between the disordered N atom on glycine 1 (G1) and the surrounding molecules was found to increase with temperature, whereas the length of the short hydrogen bond between G2 and G3 decreased slightly with temperature. This supports the suggestion that weakening of the hydrogen bonds decouples G1 from G2 and G3, allowing the system to become disordered. Except around the ferroelectric to paraelectric phase transition temperature, no abnormalities in the behaviour of any of the re ned parameters were observed, suggesting that TGS only has a single phase transition. The short-range order in TGS was investigated by collecting single crystal x-ray and neutron di use scattering at several temperatures from well below to well above TC. Well below TC, the di use scattering was purely thermal di use scattering due to correlations of the atomic displacements. Close to the phase vii viii transition, di use streaks perpendicular to b were also present in the di use scattering patterns, which were due to short-range order of the G1 orientations parallel to the ferroelectric b axis. The onset of signi cant short-range order appears to occur about 40 K below TC. The correlations are strongest at the phase transition and then decrease with temperature above TC. The short-range order was modelled using a combination of a displacive disorder and an orientational disorder Monte Carlo simulation. The intermolecular interactions that give rise to correlated atomic displacements were modelled by treating them like Hooke's law springs. The force constants for the interactions were parameterised in a number of ways, the most successful of which was an empirical formula developed by Chan et al. The short-range order of the G1 orientations was modelled using an Ising-type model. The G1 interactions that lead to short-range order along the ferroelectric b axis appear to be mediated by the short hydrogen bond between G2 and G3. This suggests that the hydrogen bonding, rather than the dipole-dipole interactions, plays the dominant role in the ferroelectric ordering of TGS. While the hydrogen bonding gives rise to strongly correlated chains of G1 molecules along b, it is likely that there are also weaker correlations between the chains due to dipole-dipole interactions. This provides a mechanism for TGS to go from short-range ordered in 1-dimension, to long-range ordered in 3-dimensions as it is cooled through TC

Temperature dependent polarization reversal mechanism in 0.94(Bi_1/2Na_1/2) TiO₃-0.06Ba(Zr_0.02Ti_0.98)O₃ relaxor ceramics

The temperature at which the electric field induced long-range ordered ferroelectric state undergoes transition into the short-range ordered relaxor state, TF-R, is commonly defined by the onset of strong dispersion of the dielectric permittivity. However, this combined macroscopic property and structural investigation of the polarization reversal process in the prototypical lead-free relaxor 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 reveals that an applied electric field can trigger depolarization and onset of relaxor-like behavior well below TF-R. The polarization reversal process can as such be described as a combination of (1) ferroelectric domain switching and (2) a reversible phase transition between two polar ferroelectric states mediated by a non-polar relaxor state. Furthermore, the threshold fields of the second, mediated polarization reversal mechanism depend strongly on temperature. These results are concomitant with a continuous ferroelectric to relaxor transition occurring over a broad temperature range, during which mixed behavior is observed. The nature of polarization reversal can be illustrated in electric-field-temperature (E-T) diagrams showing the electric field amplitudes associated with different polarization reversal processes. Such diagrams are useful tools for identifying the best operational temperature regimes for a given composition in actuator applications

Electric-field-induced paraelectric to ferroelectric phase transformation in prototypical polycrystalline BaTiO₃

An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO3 at temperatures above the Curie point (TC) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4-°C above TC. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above TC, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4-kV mm-1) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials

The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

Recent total scattering experiments have opened up the possibility to study nanoparticle formation in situ and to observe the structural transformation from precursor clusters to adult particles. Organic ligand molecules interact with precursors of metal oxide nanoparticles, yet their influence onto the evolution of crystallinity during particle formation has not been addressed in detail; nor have in situ total scattering experiments ventured into the field of low-concentration, room-temperature syntheses in organic solvents to date. In this report, we follow the crystallization of ZnO nanoparticles in ethanol in the presence of different organic ligands. Low coordinated zinc precursor clusters rapidly polymerize upon base addition to particles of ca. 1 nm in diameter. In situ SAXS experiments reveal that the overall particle size increases to 2 to 4 nm with advancing reaction time. Complementary in situ PDF experiments show smaller crystalline domain sizes, which are only one third to half as large as the particle diameter. The ZnO particles thus feature a crystalline core surrounded by a disordered shell. Both, the core and the shell diameter are influenced by the different surface-bound organic ligands, which prevent an immediate relaxation to fully crystalline particles. A slow crystallization takes place in solution. We assume a dynamic equilibrium of the ligand and solvent molecules at the particle surface, which enables gradual bond restructuring. With suitably adjusted synthesis conditions, in our case by a continuous base addition, we show how to bypass the disordered intermediates, allowing the spontaneous nucleation of fully crystalline nanoparticles