Language Processing In Aphasia Research Articles

Assessing language impairment in aphasia

Language is complicated and so, therefore, is language assessment. One complication is that there are many reasons to undertake language assessments, each of which may have different methods and goals. In this article I focus on the specific difficulties faced in aphasia assessment, the assessment of acquired language deficits. As might be expected, the history of aphasia assessment closely mirrors the history of our understanding of the neurological underpinnings of language. Early assessment was based on classical disconnection theories, dating from the 19th century, that conceptualized language as consisting of independent connected modality-specific language centers that could be disconnected by brain damage. Although these models were recognized early on as being too simplistic, aphasia assessment instruments followed the models until quite recently due to the lack of any fully specified alternative language model. It was only in the 1990s, after aphasiology had come increasingly under the influence of experimental psycholinguistics, that attempts were made to create aphasia assessment instruments that did not explicitly follow disconnection models. The most successful of these is the Psycholinguistic Assessment of Language Processing in Aphasia (PALPA; Kay, Coltheart, & Lesser, 1992). These psycholinguistically influenced instruments conceptualize language as a complex multi-dimensional system consisting of many partially independent sub-systems that may be compromised to a greater or lesser degree. Aphasia assessment instruments become longer and more detailed as a reflection of our growing understanding of the complexity of the language system. As they do, the problem of collating and integrating assessment information becomes more intractable. The future of aphasia assessment will require increasing automation to deal with the large amounts of information that must now be synthesized to fully characterize an individual deficit. I discuss recent attempts to computerize aphasia assessment and what benefits they can offer over traditional pencil-and-paper instruments.

Activity in Preserved Left Hemisphere Regions Predicts Anomia Severity in Aphasia

Understanding the neural mechanism that supports preserved language processing in aphasia has implications for both basic and applied science. This study examined brain activation associated with correct picture naming in 15 patients with aphasia. We contrasted each patient's activation to the activation observed in a neurologically healthy control group, allowing us to identify regions with unusual activity patterns. The results revealed that increased activation in preserved left hemisphere areas is associated with better naming performance in aphasia. This relationship was linear in nature; progressively less cortical activation was associated with greater severity of anomia. These findings are consistent with others who suggests that residual language function following stroke relies on preserved cortical areas in the left hemisphere.

Constraint-Induced Language Therapy: A Systematic Review

Constraint-Induced Language Therapy: A Systematic Review

Neuroimaging and recovery of language in aphasia.

The use of functional neuroimaging techniques has advanced what is known about the neural mechanisms used to support language processing in aphasia resulting from brain damage. This paper highlights recent findings derived from neuroimaging studies focused on neuroplasticity of language networks, the role of the left and right hemispheres in this process, and studies examining how treatment affects the neurobiology of recovery. We point out variability across studies as well as factors related to this variability, and we emphasize challenges that remain for research.

Semantic Memory and Language Processing: A Primer

Semantic memory refers to our long-term knowledge of word and object meaning. There is increasing evidence that rather than being a passive warehouse of knowledge, semantic memory is a dynamic system whose effectiveness relies on the coordination of multiple components distributed across a large network of cortical regions. Damage to one or more of these components produces distinct profiles of impairment in aphasia and dementia. Furthermore, such differences are associated with different responses to behavioral treatment. That is, effective treatment for semantically based language disorders in aphasia may have very limited success in dementia. We argue that treatment specificity demands a comprehensive understanding of the structure of semantic memory and the nature of its compromise. Here, we review several neuroanatomically informed theories of semantic organization with respect to the effects of semantic impairment on language processing in aphasia and neurodegenerative disease.

Semantic Memory and Language Processing in Aphasia and Dementia

Semantic Memory and Language Processing in Aphasia and Dementia

Semantic Memory and Language Processing in Aphasia and Dementia

Semantic Memory and Language Processing in Aphasia and Dementia

Widening the temporal window: Processing support in the treatment of aphasic language production

Investigations of language processing in aphasia have increasingly implicated performance factors such as slowed activation and/or rapid decay of linguistic information. This approach is supported by studies utilizing a communication system ( SentenceShaper™) which functions as a “processing prosthesis.” The system may reduce the impact of processing limitations by allowing repeated refreshing of working memory and by increasing the opportunity for aphasic subjects to monitor their own speech. Some aphasic subjects are able to produce markedly more structured speech on the system than they are able to produce spontaneously, and periods of largely independent home use of SentenceShaper have been linked to treatment effects, that is, to gains in speech produced without the use of the system. The purpose of the current study was to follow up on these studies with a new group of subjects. A second goal was to determine whether repeated, unassisted elicitations of the same narratives at baseline would give rise to practice effects, which could undermine claims for the efficacy of the system.

Reading tasks from PALPA: How do controls perform on visual lexical decision, homophony, rhyme, and synonym judgements?

Background: PALPA (Psycholinguistic Assessments of Language Processing in Aphasia; Kay, Lesser, & Coltheart, 1992) is a resource widely used by both clinicians and researchers. However, several of the subtests lack data regarding the performance of proficient English language speakers on these tasks.Aims: This paper investigates factors affecting the speed and accuracy of performance of young control participants on four assessments from PALPA: Visual lexical decision (subtest 25); synonym judgements (subtest 50); rhyme judgements (subtest 15); and homophone judgements (subtest 28).Methods and Procedures: Data are presented regarding both speed and accuracy of performance on each of the four tasks, and statistical analysis of those factors that influence performance within each test is carried out, for the participants as a group and also for the individuals within the group.Outcomes and Results: Visual lexical decision showed significant effects of frequency on response latency and accuracy, and of lexicality and imageability on response latency alone; synonym judgements showed significant effects of imageability on response latency; significant effects of word type were found on response latency for homophone judgements; for rhyme judgements there was a significant effect of rhyme for both accuracy and latency, and a significant interaction between rhyme and visual similarity.Conclusions: For the clinician seeking to interpret the performance of the person with aphasia on the tasks we have described here, we have presented data that provide some indication of the speed and accuracy of performance of young controls on these tasks. It is clear that ceiling effects in accuracy mask effects of psycholinguistic variables on normal performance that become apparent when speed of response is considered. However, performance is far from at ceiling for all the tasks described—some participants perform close to chance on some conditions. Finally, these data highlight the fact that comparison of the pattern of performance of individual participants with that of a group of controls can be problematic given the variability of control patterns of performance.

Spoken word to picture matching from PALPA: A critique and some new matched sets

Background: PALPA (Psycholinguistic Assessments of Language Processing in Aphasia; Kay, Lesser, & Coltheart, 1992) is a widely used clinical and research tool. Subtest 47, Spoken word–picture matching, requires the individual with aphasia to listen to a spoken word and correctly choose from five distractor pictures (target, close semantic, distant semantic, visually related, and semantically unrelated). It contributes diagnostically to the clinical evaluation of semantic processing. The authors claim that, first, errors on this test indicate that a semantic comprehension problem is present, and second, that distractor choice reflects the semantic specificity of the problem. For accurate clinical assessment the validity of these claims must be evaluated.Aims: This paper aims to evaluate the internal validity of PALPA spoken word–picture matching. It addresses two questions; first, is the relationship between the target and distractors what the authors claim it to be? Second, what is the relationship between the target and distractor stimuli in relation to a number of psycholinguistic variables? In addition it allows the clinician to examine the effects of individual variables on performance by including matched subsets of stimuli from this test (matched across five psycholinguistic variables: frequency, imageability, number of phonemes, semantic and visual similarity, word association).Methods and Procedures: Target and distractor relationships were investigated (in terms of semantic and visual similarity and word category) and psycholinguistic variables (including word frequency, word association, imageability, number of phonemes, semantic and visual similarity).Outcomes and Results: Analysis revealed a number of confounds within this test: close semantic distractors were not only more semantically similar but also more visually similar to their targets than distant semantic distractors; the semantic and visual (SV) close semantic distractors were more semantically similar to their targets than the non‐SV close semantic distractors; targets and distractors did not bear a consistent categorical relationship to their targets, and there were significant intercorrelations between variables for these stimuli (e.g., frequency and length; semantic/visual similarity and length).Conclusions: The authors' claim that this test assesses semantic comprehension is certainly still tenable. Individuals making errors on this test have a high probability of some semantic processing deficit. However, this study shows that the test fails to assess the nature of the semantic processing deficit, as error patterns are subject to the effect of confounding factors. In its current form clinicians should exercise caution when interpreting test findings and be aware of its limitations. The development, here, of matched subsets of stimuli allows performance to be re‐evaluated in terms of the influence of semantic and visual similarity, imageability, frequency, word length, and word association.

Phonological dyslexia and phonological dysgraphia following left and right hemispherectomy

Four adults who had hemispherectomies because of severe epilepsy following infantile of childhood damage to one hemisphere of the brain, are assessed on their reading and spelling abilities in an attempt to see if the two hemispheres are equipotential for these abilities in infancy. The psycholinguistic assessments of language processing in aphasia (PALPA) are used, and the results are interpreted from the viewpoint of hypotheses of right and left hemisphere reading abilities. Overall, the results suggest that the two hemispheres are equipotential at infancy for developing the skills underlying reading, but the left hemisphere is more specialized for the skills underlying spelling. All participants could read learnt regular and irregular words, and abstract and concrete words, suggesting that the reading lexicon develops in line with a normal left hemisphere lexicon, whichever hemisphere remains intact following hemispherectomy. However, poor reading of non-words suggests that the phonological reading route is severely impaired following left hemispherectomy (phonological dyslexia), and somewhat impaired following right hemispherectomy. The right-hemispherectomized participant is only mildly impaired on spelling real words, in contrast to the left-hemispherectomized participants who are markedly impaired. None of the participants could spell non-words, suggesting that the phonological spelling route is impaired following removal of either hemisphere (phonological dysgraphia).

Language processing in aphasia: changes in lateralization patterns during recovery reflect cerebral plasticity in adults

During single word processing the negative cortical DC-potential reveals a left frontal preponderance in normal right-handers as well as in patients with a history of transient aphasia. Lateralization of DC-negativity therefore provides a reliable and robust method for the assessment of language dominance. In 11 stroke patients with permanent aphasia this physiological pattern changed to bilateral activation reflecting an additional right-hemispheric involvement in compensatory mechanisms in aphasia. Along with complete clinical recovery the classical aphasic syndromes revealed specific differences in changes of their lateralization patterns. In Broca's aphasia the initial right-hemispheric preponderance changed to a left frontal lateralization while in Wernicke's aphasia a presumably permanent shift towards the right-hemisphere occurred. Differences in lateralization patterns might reflect different mechanisms of recovery such as the initial disinhibition of homologous areas contralaterally and subsequent collateral sprouting and synaptic modulation. The assessment of changes in lateralization of the cortical DC-potential during language tasks is a non-invasive, safe method with excellent time resolution that might provide further insights in the neural basis of recovery from aphasia.

Phonological dyslexia and phonological dysgraphia following left and right hemispherectomy

Four adults who had hemispherectomies because of severe epilepsy following infantile or childhood damage to one hemisphere of the brain, are assessed on their reading and spelling abilities in an attempt to see if the two hemispheres are equipotential for these abilities in infancy. The psycholinguistic assessments of language processing in aphasia (PALPA) are used, and the results are interpreted from the viewpoint of hypotheses of “normal” right and left hemisphere reading abilities. Overall, the results suggest that the two hemispheres are equipotential at infancy for developing the skills underlying reading, but the left hemisphere is more specialized for the skills underlying spelling. All participants could read learnt regular and irregular words, and abstract and concrete words, suggesting that the reading lexicon develops in line with a normal left hemisphere lexicon, whichever hemisphere remains intact following hemispherectomy. However, poor reading of non-words suggests that the phonological reading route is severely impaired following left hemispherectomy (phonological dyslexia), and somewhat impaired following right hemispherectomy. The right-hemispherectomized participant is only mildly impaired on spelling real words, in contrast to the left-hemispherectomized participants who are markedly impaired. None of the participants could spell non-words, suggesting that the phonological spelling route is impaired following removal of either hemisphere (phonological dysgraphia).

A real-time approach to spoken language processing in aphasia

The study is based on an on-line investigation of spoken language comprehension processes in 25 French-speaking aphasics using a syllable-monitoring task. Nonsense syllables were presented in three different conditions: context-free (embedded in strings of nonsense syllables), lexical context (where the target nonsense syllable is the initial, medial, or final syllable of real three-syllable words), and sentence context. This study builds on an earlier one that explored the relationship between the acoustic-phonetic, lexical, and sentential levels of spoken language processing in French-speaking normals and gave evidence of top-down lexical and sentential influence on syllable recognition. In the present study, aphasic patients from various diagnostic categories were classified as high ( N = 13) or low ( N = 12) comprehenders. The results show that low comprehending aphasics make no use of sentence information in the syllable-recognition task. As for top-down lexical influence, neither of the two aphasic groups demonstrates the strong context effect at the single word level that is observed in normal listeners. However, a subgroup analysis shows that the Broca's are the only high comprehending aphasics who perform in the same way as normal listeners; this sets them apart from the anomics and conduction aphasics.

A Test of Auditory Language Processing Regression: Adult Aphasia versus Normal Children Ages 5–13 Years

A total of 364 children, grouped in one year increments from five through 13 years of age, were compared to a group of 47 adult aphasic subjects on the Revised Token Test. The purpose for comparing the child groups to the aphasic group was to systematically assess a Language Processing Regression Hypothesis whereby a reduced efficiency of language processing in aphasia was compared to an increased level of language processing as a function of increased age of the normal children. Using discriminant analyses, the patterns of test performance were compared between the aphasic and each of the child groups. The number of subjects misclassified (children as adult aphasic, or adult, aphasic as children) was minimal for all of the comparisons and serves as counterevidence for the Regression Hypothesis. The numbers of subjects correctly classified into their respective groups was low for comparisons with the 5 through 9 year groups, where the bulk of the subjects were unclassifiable. However, a precipitous rise i...

The syndrome of Gogi (word meaning) aphasia. Selective impairment of kanji processing.

In 1943, Imura described an aphasic syndrome shown by Japanese patients and designated it as Gogi ("word-meaning") aphasia. Salient features are selective impairment of processing kanji or Chinese characters and difficulty in finding access to the lexicon in both production and reception, with preservation of processing kana or phonetic signs, and fluent oral repetition. A patient with this syndrome is presented, with emphasis on the nature of his kanji impairment. Cases of Gogi aphasia in the literature are reviewed and contrasted to cases of Broca's aphasia with selective impairment of kana processing. The implications for a neurolinguistic model of language processing in aphasia are discussed.

Kana and kanji processing in japanese aphasics

Evidence is presented indicating that the ability of Japanese aphasics to use Japanese kana signs (phonetic symbols for syllables) and kanji characters (essentially nonphonetic logographic symbols) can be selectively impaired. Three types of impairment can be distinguished in terms of the characteristic patterns of kana versus kanji disabilities, which appear to correlate with some of the major diagnostic categories recognized among speakers of Indo-European languages, such as Broca's Aphasia, Wernicke's Aphasia, and Transcortical Aphasia. The results of longitudinal studies made of a limited number of patients representing each type indicate that the recovery processes for kana and kanji impairment are significantly different from type to type. The theoretical implications of these findings for a model of language processing in aphasia is discussed.