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Harvey D.Y.,Rice University | Harvey D.Y.,University of Pennsylvania | Harvey D.Y.,Moss Rehabilitation Research Institute | Schnur T.T.,Rice University

Naming pictures and matching words to pictures belonging to the same semantic category negatively affects language production and comprehension. By most accounts, semantic interference arises when accessing lexical representations in naming (e.g., Damian, Vigliocco, & Levelt, 2001) and semantic representations in comprehension (e.g., Forde & Humphreys, 1997). Further, damage to the left inferior frontal gyrus (LIFG), a region implicated in cognitive control, results in increasing semantic interference when items repeat across cycles in both language production and comprehension (Jefferies, Baker, Doran, & Lambon Ralph, 2007). This generates the prediction that the LIFG via white matter connections supports resolution of semantic interference arising from different loci (lexical vssemantic) in the temporal lobe. However, it remains unclear whether the cognitive and neural mechanisms that resolve semantic interference are the same across tasks. Thus, we examined which gray matter structures [using whole brain and region of interest (ROI) approaches] and white matter connections (using deterministic tractography) when damaged impact semantic interference and its increase across cycles when repeatedly producing and understanding words in 15 speakers with varying lexical-semantic deficits from left hemisphere stroke. We found that damage to distinct brain regions, the posterior versusanterior temporal lobe, was associated with semantic interference (collapsed across cycles) in naming and comprehension, respectively. Further, those with LIFG damage compared to those without exhibited marginally larger increases in semantic interference across cycles in naming but not comprehension. Lastly, the inferior fronto-occipital fasciculus, connecting the LIFG with posterior temporal lobe, related to semantic interference in naming, whereas the inferior longitudinal fasciculus (ILF), connecting posterior with anterior temporal regions related to semantic interference in comprehension. These neuroanatomical-behavioral findings have implications for models of the lexical-semantic language network by demonstrating that semantic interference in language production and comprehension involves different representations which differentially recruit a cognitive control mechanism for interference resolution. © 2015 Elsevier Ltd. Source

Hart T.,Moss Rehabilitation Research Institute | Bagiella E.,Columbia University
Archives of Physical Medicine and Rehabilitation

The growth of evidence-based medicine means that both researchers and clinicians must grasp the complex issues involved in implementing clinical trials, which are especially challenging for the behavioral (experience-based) treatments that predominate in rehabilitation. In this article we discuss selected issues germane to the design, implementation, and analysis of group-level clinical trials in rehabilitation. We review strengths, weaknesses, and best applications of 1-sample, between-subjects, and within-subjects study designs, including newer models such as practical clinical trials and point-of-care trials. We also discuss the selection of appropriate control conditions against which to test rehabilitation treatments, as well as issues related to trial blinding. In a section on treatment definition, we discuss the challenges of specifying the active ingredients in the complex interventions that are widely used in rehabilitation, and present an illustration of 1 approach to defining treatments via the learning mechanisms that underlie them. Issues related to treatment implementation are also discussed, including therapist allocation and training, and assessment of treatment fidelity. Finally we consider 2 statistical topics of particular importance to many rehabilitation trials: the use of multiple or composite outcomes, and factors that must be weighed in estimating sample size for clinical trials. © 2012 American Congress of Rehabilitation Medicine. Source

Lupyan G.,University of Wisconsin - Madison | Mirman D.,Moss Rehabilitation Research Institute

In addition to its use in communication, language appears to have a variety of extra-communicative functions; disrupting language disrupts performance in seemingly non-linguistic tasks. Previous work has specifically linked linguistic impairments to categorization impairments. Here, we systematically tested this link by comparing categorization performance in a group of 12 participants with aphasia and 12 age- and education-matched control participants. Participants were asked to choose all of the objects that fit a specified criterion from sets of 20 pictured objects. The criterion was either " high-dimensional" (i.e., the objects shared many features, such as " farm animals") or " low-dimensional" (i.e., the objects shared one or a few features, such as " things that are green" ). Participants with aphasia were selectively impaired on low-dimensional categorization. This selective impairment was correlated with the severity of their naming impairment and not with the overall severity of their aphasia, semantic impairment, lesion size, or lesion location. These results indicate that linguistic impairment impacts categorization specifically when that categorization requires focusing attention and isolating individual features - a task that requires a larger degree of cognitive control than high-dimensional categorization. The results offer some support for the hypothesis that language supports cognitive functioning, particularly the ability to select task-relevant stimulus features. © 2012 Elsevier Ltd. Source

Whyte J.,Moss Rehabilitation Research Institute
Archives of Physical Medicine and Rehabilitation

Scientific theory is crucial to the advancement of clinical research. The breadth of rehabilitation treatment requires that many different theoretical perspectives be incorporated into the design and testing of treatment interventions. In this article, the 2 broad classes of theory relevant to rehabilitation research and practice are defined, and their distinct but complementary contributions to research and clinical practice are explored. These theory classes are referred to as treatment theories (theories about how to effect change in clinical targets) and enablement theories (theories about how changes in a proximal clinical target will influence distal clinical aims). Treatment theories provide the tools for inducing clinical change but do not specify how far reaching the ultimate impact of the change will be. Enablement theories model the impact of changes on other areas of function but provide no insight as to how treatment can create functional change. Treatment theories are more critical in the early stages of treatment development, whereas enablement theories become increasingly relevant in specifying the clinical significance and practical effectiveness of more mature treatments. Understanding the differences in the questions these theory classes address and how to combine their insights is crucial for effective research development and clinical practice. © 2014 by the American Congress of Rehabilitation Medicine. Source

Schwartz M.F.,Moss Rehabilitation Research Institute
Philosophical Transactions of the Royal Society B: Biological Sciences

The cognitive analysis of adult language disorders continues to draw heavily on linguistic theory, but increasingly it reflects the influence of connectionist, spreading activation models of cognition. In the area of spoken word production, 'localist' connectionist models represent a natural evolution from the psycholingistic theories of earlier decades. By contrast, the parallel distributed processing framework forces more radical rethinking of aphasic impairments. This paper exemplifies these multiple influences in contemporary cognitive aphasiology. Topics include (i) what aphasia reveals about semantic-phonological interaction in lexical access; (ii) controversies surrounding the interpretation of semantic errors and (iii) a computational account of the relationship between naming and word repetition in aphasia. Several of these topics have been addressed using case series methods, including computational simulation of the individual, quantitative error patterns of diverse groups of patients and analysis of brain lesions that correlate with error rates and patterns. Efforts to map the lesion correlates of nonword errors in naming and repetition highlight the involvement of sensorimotor areas in the brain and suggest the need to better integrate models of word production with models of speech and action. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source

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