Chaleece Sandberg

Treatment for lexical retrieval using abstract and concrete words in persons with aphasia: Effect of complexity

Background: The significance of imageability and concreteness as factors for lexical tasks in aphasic individuals is under debate. No previous treatment studies have looked specifically at training abstract words compared to concrete for improved lexical retrieval in patients with chronic aphasia. Aims: The goal of the present study was to determine the efficacy of a treatment for lexical retrieval that is based on models of lexical processing by utilising abstractness as a mode of complexity. It was hypothesised that training abstract words in a category will result in improvement of those words and generalisation to untrained target concrete words in the same category. However, training concrete words in a category will result in the retrieval of trained concrete words, but not generalisation to target abstract words. Methods & Procedures: A single‐participant experimental design across participants and behaviours was used to examine treatment and generalisation. Generative naming for three categories (church, hospital, courthouse) was tested during baseline and treatment. Each treatment session was carried out in five steps: (1) category sorting, (2) feature selection, (3) yes/no feature questions, (4) word recall, and (5) free generative naming. Outcomes & Results: Although participant 1 demonstrated neither significant learning nor generalisation during abstract or concrete word training, participants 2, 3, and 4 showed significant learning during abstract word training and generalisation to untrained concrete words. Participants 3 and 4 were also trained on concrete words, on which they improved, but did not show generalisation to untrained abstract words. Conclusions: The results of the present experiment support our hypothesis that training abstract words would result in greater learning and generalisation to untrained concrete words. They also tentatively support the idea that generalisation is facilitated by treatment focusing on more complex constructions (Kiran & Thompson, 2003; Thompson, Shapiro, Kiran, & Sobecks, 2003).

The relationships between the amount of spared tissue, percent signal change, and accuracy in semantic processing in aphasia.

Recovery from aphasia, loss of language following a cerebrovascular incident (stroke), is a complex process involving both left and right hemispheric regions. In our study, we analyzed the relationships between semantic processing behavioral data, lesion size and location, and percent signal change from functional magnetic resonance imaging (fMRI) data. This study included 14 persons with aphasia in the chronic stage of recovery (six or more months post stroke), along with normal controls, who performed semantic processing tasks of determining whether a written semantic feature matched a picture or whether two written words were related. Using region of interest (ROI) analysis, we found that left inferior frontal gyrus pars opercularis and pars triangularis, despite significant damage, were the only regions to correlate with behavioral accuracy. Additionally, bilateral frontal regions including superior frontal gyrus, middle frontal gyrus, and anterior cingulate appear to serve as an assistive network in the case of damage to traditional language regions that include inferior frontal gyrus, middle temporal gyrus, supramarginal gyrus, and angular gyrus. Right hemisphere posterior regions including right middle temporal gyrus, right supramarginal gyrus, and right angular gyrus are engaged in the case of extensive damage to left hemisphere language regions. Additionally, right inferior frontal gyrus pars orbitalis is presumed to serve a monitoring function. These results reinforce the importance of the left hemisphere in language processing in aphasia, and provide a framework for the relative importance of left and right language regions in the brain.

A rational inference approach to aphasic language comprehension

ABSTRACT Background: It has long been observed that, when confronted with an implausible sentence like The ball kicked the girl, individuals with aphasia rely more on plausibility information from world knowledge (such that a girl is likely to kick a ball, but not vice versa) than control non-impaired populations do. We here offer a novel hypothesis to explain this greater reliance on plausibility information for individuals with aphasia. The hypothesis is couched with the rational inference approach to language processing. A key idea in this approach is that to derive an interpretation for an input string, individuals combine their priors (about messages that are likely to be communicated) with their knowledge about how messages can get corrupted by noise (due to production or perception errors). Aims: We hypothesise that language comprehension in aphasia works in the same way, except with a greater amount of noise, which leads to stronger reliance on syntactic and semantic priors. Methods & Procedures: We evaluated this hypothesis in an act-out task in three groups of participants (8 individuals with aphasia, 7 older controls, 11 younger controls) on two sets of materials: (a) implausible double-object (DO)/prepositional-phrase object (PO) materials, where a single added or deleted word could lead to a plausible meaning; and (b) implausible active-passive materials, where at least two added or deleted words are needed to arrive at a plausible meaning. Outcomes & Results: We observed that, similar to controls, individuals with aphasia rely on plausibility to a greater extent in the DO/PO than in the active/passive alternation. Critically, however, as predicted, individuals with aphasia rely less on the literal syntax overall than either of the control groups, and use their world knowledge prior (plausibility) in both the active/passive and DO/PO alternations, whereas controls rely on plausibility only in the DO/PO alternation. In addition, older persons and persons with aphasia made more errors on the DO structures (which are less frequent than PO structures) independent of plausibility, thus providing evidence for reliance on a syntactic prior, the more frequent structure. Conclusions: These results are as predicted by the rational inference approach to language processing in individuals with aphasia.

Changes in functional connectivity related to direct training and generalization effects of a word finding treatment in chronic aphasia.

The neural mechanisms that underlie generalization of treatment-induced improvements in word finding in persons with aphasia (PWA) are currently poorly understood. This study aimed to shed light on changes in functional network connectivity underlying generalization in aphasia. To this end, we used fMRI and graph theoretic analyses to examine changes in functional connectivity after a theoretically-based word-finding treatment in which abstract words were used as training items with the goal of promoting generalization to concrete words. Ten right-handed native English-speaking PWA (7 male, 3 female) ranging in age from 47 to 75 (mean=59) participated in this study. Direct training effects coincided with increased functional connectivity for regions involved in abstract word processing. Generalization effects coincided with increased functional connectivity for regions involved in concrete word processing. Importantly, similarities between training and generalization effects were noted as were differences between participants who generalized and those who did not.

Hypoconnectivity of Resting-State Networks in Persons with Aphasia Compared with Healthy Age-Matched Adults

Aphasia is a language disorder affecting more than one million people in the US. While language function has traditionally been the focus of neuroimaging research, other cognitive functions are affected in this population, which has implications not only for those specific processes but also for the interaction of language and other cognitive functions. Resting state fMRI (rs-fMRI) is a practical and informative way to explore and characterize general cognitive engagement and/or health in this population, but it is currently underutilized. The aim of this study was to explore the functional connectivity in resting state networks (RSNs) and in the semantic network in seven persons with aphasia (PWA) who were at least 6 months post onset compared with 11 neurologically healthy adults (NHA) in order to gain a more comprehensive understanding of general cognitive engagement in aphasia. These preliminary results show that PWA exhibit hypoconnectivity in the semantic network and all RSNs except the visual network. Compared with NHA, PWA appear to have fewer cross- and left-hemispheric connections. However, PWA exhibit some stronger connections than NHA within the semantic network, which could indicate compensatory mechanisms. Importantly, connectivity for RSNs appear to increase with decreasing aphasia severity and decrease with increasing lesion size. This knowledge has the potential to improve aphasia therapy by furthering the understanding of lesion effects on the cognitive system as a whole, which can guide treatment target selection and promotion of favorable neural reorganization for optimal recovery of function.

Analysis of abstract and concrete word processing in persons with aphasia and age-matched neurologically healthy adults using fMRI

The concreteness effect occurs in both normal and language-disordered populations. Research suggests that abstract and concrete concepts elicit differing neural activation patterns in healthy young adults, but this is undocumented in persons with aphasia (PWA). Three PWA and three age-matched controls were scanned using fMRI while processing abstract and concrete words. Consistent with current theories of abstract and concrete word processing, abstract words elicited activation in verbal areas, whereas concrete words additionally activated multimodal association areas. PWA show greater differences in neural activation than age-matched controls between abstract and concrete words, possibly due to an exaggerated concreteness effect.

A Computational Account of Bilingual Aphasia Rehabilitation.

Current research on bilingual aphasia highlights the paucity in recommendations for optimal rehabilitation for bilingual aphasic patients (Roberts & Kiran, 2007; Edmonds & Kiran, 2006). In this paper, we have developed a computational model to simulate an English-Spanish bilingual language system in which language representations can vary by age of acquisition (AoA) and relative proficiency in the two languages to model individual participants. This model is subsequently lesioned by varying connection strengths between the semantic and phonological networks and retrained based on individual patient demographic information to evaluate whether or not the models prediction of rehabilitation matched the actual treatment outcome. In most cases the model comes close to the target performance subsequent to language therapy in the language trained, indicating the validity of this model in simulating rehabilitation of naming impairment in bilingual aphasia. Additionally, the amount of cross-language transfer is limited both in the patient performance and in the models predictions and is dependent on that specific patients AoA, language exposure and language impairment. It also suggests how well alternative treatment scenarios would have fared, including some cases where the alternative would have done better. Overall, the study suggests how computational modeling could be used in the future to design customized treatment recipes that result in better recovery than is currently possible.

Typicality mediates performance during category verification in both ad-hoc and well-defined categories

BACKGROUND The typicality effect is present in neurologically intact populations for natural, ad-hoc, and well-defined categories. Although sparse, there is evidence of typicality effects in persons with chronic stroke aphasia for natural and ad-hoc categories. However, it is unknown exactly what influences the typicality effect in this population. AIMS The present study explores the possible contributors to the typicality effect in persons with aphasia by analyzing and comparing data from both normal and language-disordered populations, from persons with aphasia with more semantic impairment versus those with less semantic impairment, and from two types of categories with very different boundary structure (ad-hoc vs. well-defined). METHODS AND PROCEDURES A total of 40 neurologically healthy adults (20 older, 20 younger) and 35 persons with aphasia (20 LSI (less-semantically impaired) patients, 15 MSI (more-semantically impaired) patients) participated in the study. Participants completed one of two tasks: either category verification for ad-hoc categories or category verification for well-defined categories. OUTCOMES AND RESULTS Neurologically healthy participants showed typicality effects for both ad-hoc and well-defined categories. MSI patients showed a typicality effect for well-defined categories, but not for ad-hoc categories, whereas LSI patients showed a typicality effect for ad-hoc categories, but not for well-defined categories. CONCLUSIONS These results suggest that the degree of semantic impairment mediates the typicality effect in persons with aphasia depending on the structure of the category. LEARNING OUTCOMES After reading this article, the reader should be able to: (1) Describe the typicality effect and in which populations it occurs. (2) Explain how the typicality effect might change depending on category structure. (3) summarize how semantic impairment influences category representation and/or access.

How justice can affect jury: training abstract words promotes generalisation to concrete words in patients with aphasia.

Developing language treatments that not only improve trained items but also promote generalisation to untrained items is a major focus in aphasia research. This study is a replication and extension of previous work which found that training abstract words in a particular context-category promotes generalisation to concrete words but not vice versa (Kiran, Sandberg, & Abbott, 2009). Twelve persons with aphasia (five female) with varying types and degrees of severity participated in a generative naming treatment based on the Complexity Account of Treatment Efficacy (CATE; Thompson, Shapiro, Kiran, & Sobecks, 2003). All participants were trained to generate abstract words in a particular context-category by analysing the semantic features of the target words. Two other context-categories were used as controls. Ten of the twelve participants improved on the trained abstract words in the trained context-category. Eight of the ten participants who responded to treatment also generalised to concrete words in the same context-category. These results suggest that this treatment is both efficacious and efficient. We discuss possible mechanisms of training and generalisation effects.

Impairment and rehabilitation in bilingual aphasia: a SOM-based model

Bilingual aphasia is of increasing interest because a large and growing proportion of the worlds population is bilingual. Current clinical research on this topic cannot provide specific recommendations on which language treatment should focus in a bilingual aphasic individual and to what extent cross-language transfer occurs during or after rehabilitation. This paper describes a SOM-based model of the bilingual lexicon, and reports on simulations of impairment and rehabilitation in bilingual aphasia. The goal is to create computational methods that can complement clinical research in developing a better understanding of mechanisms underlying recovery, and that could be used in the future to predict the most beneficial treatment for individual patients.