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The present study examined spontaneous detection and repair of naming errors in people with aphasia to advance a theoretical understanding of how monitoring impacts learning in lexical access. Prior work in aphasia has found that spontaneous repair, but not mere detection without repair, of semantic naming errors leads to improved naming on those same items in the future when other factors are accounted for. The present study sought to replicate this finding in a new, larger sample of participants and to examine the critical role of self-generated repair in this monitoring learning effect. Twenty-four participants with chronic aphasia with naming impairment provided naming responses to a 660-item corpus of common, everyday objects at two timepoints. At the first timepoint, a randomly selected subset of trials ended in experimenter-provided corrective feedback. Each naming trial was coded for accuracy, error type, and for any monitoring behavior that occurred, specifically detection with repair (i.e., correction), detection without repair, and no detection. Focusing on semantic errors, the original monitoring learning effect was replicated, with enhanced accuracy at a future timepoint when the first trial with that item involved detection with repair, compared to error trials that were not detected. This enhanced accuracy resulted from learning that arose from the first trial rather than the presence of repair simply signifying easier items. A second analysis compared learning from trials of self-corrected errors to that of trials ending in feedback that were detected but not self-corrected and found enhanced learning after self-generated repair. Implications for theories of lexical access and monitoring are discussed.

The severity of post-stroke aphasia and the potential for recovery are highly variable and difficult to predict. Evidence suggests that optimal estimation of aphasia severity requires the integration of multiple neuroimaging modalities and the adoption of new methods that can detect multivariate brain-behavior relationships. We created and tested a multimodal framework that relies on three information sources (lesion maps, structural connectivity, and functional connectivity) to create an array of unimodal predictions which are then fed into a final model that creates "stacked multimodal predictions" (STAMP). Crossvalidated predictions of four aphasia scores (picture naming, sentence repetition, sentence comprehension, and overall aphasia severity) were obtained from 53 left hemispheric chronic stroke patients (age: 57.1 ± 12.3 yrs, post-stroke interval: 20 months, 25 female). Results showed accurate predictions for all four aphasia scores (correlation true vs. predicted: r = 0.79-0.88). The accuracy was slightly smaller but yet significant (r = 0.66) in a full split crossvalidation with each patient considered as new. Critically, multimodal predictions produced more accurate results that any single modality alone. Topological maps of the brain regions involved in the prediction were recovered and compared with traditional voxel-based lesion-to-symptom maps, revealing high spatial congruency. These results suggest that neuroimaging modalities carry complementary information potentially useful for the prediction of aphasia scores. More broadly, this study shows that the translation of neuroimaging findings into clinically useful tools calls for a shift in perspective from unimodal to multimodal neuroimaging, from univariate to multivariate methods, from linear to nonlinear models, and, conceptually, from inferential to predictive brain mapping. Hum Brain Mapp 38:5603-5615, 2017. © 2017 Wiley Periodicals, Inc.

Fluent speech production is a critical aspect of language processing and is central to aphasia diagnosis and treatment. Multiple cognitive processes and neural sub-systems must be coordinated to produce fluent narrative speech. To refine the understanding of these systems, measures that minimize the influence of other cognitive processes were defined for articulatory deficits and grammatical deficits. Articulatory deficits were measured by the proportion of phonetic errors (articulatory and prosodic) in a word repetition task in 115 participants with aphasia following left hemisphere stroke. Grammatical deficits were assessed in 46 participants based on two measures – proportion of closed class words and proportion of words in sentences – generated during semi-structured narrative speech production (telling the Cinderella story). These measures were used to identify brain regions critical for articulatory and grammatical aspects of speech production using a multivariate lesion-symptom mapping approach based on support vector regression. Phonetic error proportion was associated with damage to the postcentral gyrus and the inferior parietal lobule (particularly the supramarginal gyrus). Proportion of closed class words in narrative speech did not have consistent lesion correlates. Proportion of words in sentences was strongly associated with frontal lobe damage, particularly the inferior and middle frontal gyri. Grammatical sentence structuring relies on frontal regions, particularly the inferior and middle frontal gyri, whereas phonetic-articulatory planning and execution relies on parietal regions, particularly the postcentral and supramarginal gyri. These results clarify and extend current understanding of the functional components of the fronto-parietal speech production system.

Purpose The purpose of this article was to examine how different types of learning experiences affect naming impairment in aphasia. Methods In 4 people with aphasia with naming impairment, we compared the benefits of naming treatment that emphasized retrieval practice (practice retrieving target names from long-term memory) with errorless learning (repetition training, which preempts retrieval practice) according to different schedules of learning. The design was within subjects. Items were administered for multiple training trials for retrieval practice or repetition in a spaced schedule (an item's trials were separated by multiple unrelated trials) or massed schedule (1 trial intervened between an item's trials). In the spaced condition, we studied 3 magnitudes of spacing to evaluate the impact of effortful retrieval during training on the ultimate benefits conferred by retrieval practice naming treatment. The primary outcome was performance on a retention test of naming after 1 day, with a follow-up test after 1 week. Results Group analyses revealed that retrieval practice outperformed errorless learning, and spaced learning outperformed massed learning at retention test and at follow-up. Increases in spacing in the retrieval practice condition yielded more robust learning of retrieved information. Conclusion This study delineates the importance of retrieval practice and spacing for treating naming impairment in aphasia. Supplemental Material https://doi.org/10.23641/asha.14963925

The gold standard for identifying stroke lesions is manual tracing, a method that is known to be observer dependent and time consuming, thus impractical for big data studies. We propose LINDA (Lesion Identification with Neighborhood Data Analysis), an automated segmentation algorithm capable of learning the relationship between existing manual segmentations and a single T1-weighted MRI. A dataset of 60 left hemispheric chronic stroke patients is used to build the method and test it with k-fold and leave-one-out procedures. With respect to manual tracings, predicted lesion maps showed a mean dice overlap of 0.696 ± 0.16, Hausdorff distance of 17.9 ± 9.8 mm, and average displacement of 2.54 ± 1.38 mm. The manual and predicted lesion volumes correlated at r = 0.961. An additional dataset of 45 patients was utilized to test LINDA with independent data, achieving high accuracy rates and confirming its cross-institutional applicability. To investigate the cost of moving from manual tracings to automated segmentation, we performed comparative lesion-to-symptom mapping (LSM) on five behavioral scores. Predicted and manual lesions produced similar neuro-cognitive maps, albeit with some discussed discrepancies. Of note, region-wise LSM was more robust to the prediction error than voxel-wise LSM. Our results show that, while several limitations exist, our current results compete with or exceed the state-of-the-art, producing consistent predictions, very low failure rates, and transferable knowledge between labs. This work also establishes a new viewpoint on evaluating automated methods not only with segmentation accuracy but also with brain–behavior relationships. LINDA is made available online with trained models from over 100 patients. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc.

Clinicians have long appreciated that people with aphasia (PWA) who self-monitor their errorful speech have better outcomes. It has been assumed, with empirical justification, that this is because successful monitoring is associated with a stronger language system, and a robust system is more likely to improve (Strength hypothesis). A second possibility, not incompatible with the first, is that monitoring success in some way causes those language systems to undergo adaptive change (Learning hypothesis). This chapter describes recent evidence from PWA’s self-monitoring of naming errors that supports both the strength and learning hypotheses. A follow-up analysis of monitoring latencies speaks to differences in repair processes for semantic and phonological errors. The discussion develops an explanatory framework that integrates aspects of monitoring theory with models of lexical access and incremental learning.

Although the parietal lobe was considered by many of the earliest investigators of disordered language to be a major component of the neural systems instantiating language, most views of the anatomic substrate of language emphasize the role of temporal and frontal lobes in language processing. We review evidence from lesion studies as well as functional neuroimaging, demonstrating that the left parietal lobe is also crucial for several aspects of language. First, we argue that the parietal lobe plays a major role in semantic processing, particularly for "thematic" relationships in which information from multiple sensory and motor domains is integrated. Additionally, we review a number of accounts that emphasize the role of the left parietal lobe in phonologic processing. Although the accounts differ somewhat with respect to the nature of the linguistic computations subserved by the parietal lobe, they share the view that the parietal lobe is essential for the processes by which sound-based representations are transcoded into a format that can drive action systems. We suggest that investigations of the linguistic capacities of the parietal lobe constrained by the understanding of the parietal lobe in action and multimodal sensory integration may serve to enhance not only our understanding of language, but also the relationship between language and more basic brain functions.

Although the parietal lobe was considered by many of the earliest investigators of disordered language to be a major component of the neural systems instantiating language, most views of the anatomic substrate of language emphasize the role of temporal and frontal lobes in language processing. We review evidence from lesion studies as well as functional neuroimaging, demonstrating that the left parietal lobe is also crucial for several aspects of language. First, we argue that the parietal lobe plays a major role in semantic processing, particularly for "thematic" relationships in which information from multiple sensory and motor domains is integrated. Additionally, we review a number of accounts that emphasize the role of the left parietal lobe in phonologic processing. Although the accounts differ somewhat with respect to the nature of the linguistic computations subserved by the parietal lobe, they share the view that the parietal lobe is essential for the processes by which sound-based representations are transcoded into a format that can drive action systems. We suggest that investigations of the linguistic capacities of the parietal lobe constrained by the understanding of the parietal lobe in action and multimodal sensory integration may serve to enhance not only our understanding of language, but also the relationship between language and more basic brain functions.

This essay discusses the intellectual developments in psychology, linguistics, and behavioral neurology that shaped Oscar Marin’s approach to disorders of high cortical function. As Chief of Neurology at Baltimore City Hospitals in the 1970s, Dr Marin teamed with biopsychologist Eleanor Saffran and the author in seminal studies of acquired language disorders (aphasia) centering on core processes of syntax and semantics, and rejecting premature reductionism. The philosophical and methodological principles that motivated these studies are traced through the author’s personal recollections and the published writings of the Marin lab. These principles came to be associated with the cognitive neuropsychology school of research and have important linkages to contemporary work in the neuroscience of aphasia and related cognitive disorders.

Because individuals with acquired language disorders are frequently unable to reliably access the names of common everyday objects (i.e., naming impairment), rehabilitation efforts often focus on improving naming. The present study compared two rehabilitation strategies for naming impairment, reflecting contradictory prescriptions derived from different theoretical principles. The prescription derived from psychological research on test-enhanced learning advocates providing patients opportunities to retrieve target names from long-term memory (i.e., retrieval practice) in the course of treatment. In contrast, the errorless learning approach derived from cognitive rehabilitation research eschews retrieval practice in favor of methods that minimize naming errors, and thus the potential for error learning, in the course of treatment. The present study directly compared these approaches and showed that, despite superior (and errorless) performance during errorless treatment, treatment that prioritized retrieval practice produced greater retention 1-day and 1-week following treatment. These findings have implications for clinical practice, as well as theoretical accounts of lexical access and test-enhanced learning.

This study examined the timing of spontaneous self-monitoring in the naming responses of people with aphasia. Twelve people with aphasia completed a 615-item naming test twice, in separate sessions. Naming attempts were scored for accuracy and error type, and verbalizations indicating detection were coded as negation (e.g., "no, not that") or repair attempts (i.e., a changed naming attempt). Focusing on phonological and semantic errors, we measured the timing of the errors and of the utterances that provided evidence of detection. The effects of error type and detection response type on error-to-detection latencies were analyzed using mixed-effects regression modeling. We first asked whether phonological errors and semantic errors differed in the timing of the detection process or repair planning. Results suggested that the two error types primarily differed with respect to repair planning. Specifically, repair attempts for phonological errors were initiated more quickly than repair attempts for semantic errors. We next asked whether this difference between the error types could be attributed to the tendency for phonological errors to have a high degree of phonological similarity with the subsequent repair attempts, thereby speeding the programming of the repairs. Results showed that greater phonological similarity between the error and the repair was associated with faster repair times for both error types, providing evidence of error-to-repair priming in spontaneous self-monitoring. When controlling for phonological overlap, significant effects of error type and repair accuracy on repair times were also found. These effects indicated that correct repairs of phonological errors were initiated particularly quickly, whereas repairs of semantic errors were initiated relatively slowly, regardless of their accuracy. We discuss the implications of these findings for theoretical accounts of self-monitoring and the role of speech error repair in learning.

The severity of post-stroke aphasia and the potential for recovery are highly variable and difficult to predict. Evidence suggests that optimal estimation of aphasia severity requires the integration of multiple neuroimaging modalities and the adoption of new methods that can detect multivariate brain-behavior relationships. We created and tested a multimodal framework that relies on three information sources (lesion maps, structural connectivity, and functional connectivity) to create an array of unimodal predictions which are then fed into a final model that creates "stacked multimodal predictions" (STAMP). Crossvalidated predictions of four aphasia scores (picture naming, sentence repetition, sentence comprehension, and overall aphasia severity) were obtained from 53 left hemispheric chronic stroke patients (age: 57.1 ± 12.3 yrs, post-stroke interval: 20 months, 25 female). Results showed accurate predictions for all four aphasia scores (correlation true vs. predicted: r = 0.79-0.88). The accuracy was slightly smaller but yet significant (r = 0.66) in a full split crossvalidation with each patient considered as new. Critically, multimodal predictions produced more accurate results that any single modality alone. Topological maps of the brain regions involved in the prediction were recovered and compared with traditional voxel-based lesion-to-symptom maps, revealing high spatial congruency. These results suggest that neuroimaging modalities carry complementary information potentially useful for the prediction of aphasia scores. More broadly, this study shows that the translation of neuroimaging findings into clinically useful tools calls for a shift in perspective from unimodal to multimodal neuroimaging, from univariate to multivariate methods, from linear to nonlinear models, and, conceptually, from inferential to predictive brain mapping. Hum Brain Mapp 38:5603-5615, 2017. © 2017 Wiley Periodicals, Inc.

Lesion analysis is a classic approach to study brain functions. Because brain function is a result of coherent activations of a collection of functionally related voxels, lesion-symptom relations are generally contributed by multiple voxels simultaneously. Although voxel-based lesion-symptom mapping (VLSM) has made substantial contributions to the understanding of brain-behavior relationships, a better understanding of the brain-behavior relationship contributed by multiple brain regions needs a multivariate lesion-symptom mapping (MLSM). The purpose of this artilce was to develop an MLSM using a machine learning-based multivariate regression algorithm: support vector regression (SVR). In the proposed SVR-LSM, the symptom relation to the entire lesion map as opposed to each isolated voxel is modeled using a nonlinear function, so the intervoxel correlations are intrinsically considered, resulting in a potentially more sensitive way to examine lesion-symptom relationships. To explore the relative merits of VLSM and SVR-LSM we used both approaches in the analysis of a synthetic dataset. SVR-LSM showed much higher sensitivity and specificity for detecting the synthetic lesion-behavior relations than VLSM. When applied to lesion data and language measures from patients with brain damages, SVR-LSM reproduced the essential pattern of previous findings identified by VLSM and showed higher sensitivity than VLSM for identifying the lesion-behavior relations. Our data also showed the possibility of using lesion data to predict continuous behavior scores.

The dual-route interactive two-step model explains the variation in the error patterns of aphasic speakers in picture naming, and word and nonword repetition tasks. The model has three parameters that can vary across individuals: the efficiency of the connections between semantic and lexical representations (s-weight), between lexical and phonological representations (p-weight), and between representations of auditory input and phonological representations (nl-weight). We determined these parameter values in 103 participants with chronic aphasia from left hemisphere stroke whose lesion locations had been determined. Then, using voxel-based lesion-parameter mapping, we mapped the parameters onto the brain, thus determining the neural correlates of the model's mechanisms. The maps and the behavioral findings supported the model's central claim that word repetition is affected by both the p and nl parameters. We propose that these two parameters constitute the model's analogue of the "dorsal stream" component of neurocognitive models of language processing.

Ventrolateral prefrontal cortex (VLPFC) has long been linked to language production, but the precise mechanisms are still being elucidated. Using neuropsychological case studies, we explored possible sub-specialization within this region for different linguistic and executive functions. Frontal patients with different lesion profiles completed two sequencing tasks, which were hypothesized to engage partially overlapping components. The multi-word priming task tested the sequencing of co-activated representations and the overriding of primed word orders. The sequence reproduction task tested the sequencing of co-activated representations, but did not employ a priming manipulation. We compared patients' performance on the two tasks to that of healthy, age-matched controls. Results are partially consistent with an anterior–posterior gradient of cognitive control within lateral prefrontal cortex ( Koechlin & Summerfield, 2007 ). However, we also found a stimulus-specific pattern, which suggests that sub-specialization might be contingent on type of representation as well as type of control signal. Isolating such components functionally and anatomically might lead to a better understanding of language production deficits in aphasia.

This study examined spontaneous self-monitoring of picture naming in people with aphasia. Of primary interest was whether spontaneous detection or repair of an error constitutes an error signal or other feedback that tunes the production system to the desired outcome. In other words, do acts of monitoring cause adaptive change in the language system? A second possibility, not incompatible with the first, is that monitoring is indicative of an item’s representational strength, and strength is a causal factor in language change. Twelve PWA performed a 615-item naming test twice, in separate sessions, without extrinsic feedback. At each timepoint, we scored the first complete response for accuracy and error type and the remainder of the trial for verbalizations consistent with detection (e.g., “no, not that”) and successful repair (i.e., correction). Data analysis centered on: (a) how often an item that was misnamed at one timepoint changed to correct at the other timepoint, as a function of monitoring; and (b) how monitoring impacted change scores in the Forward (Time 1 to Time 2) compared to Backward (Time 2 to Time 1) direction. The Strength hypothesis predicts significant effects of monitoring in both directions. The Learning hypothesis predicts greater effects in the Forward direction. These predictions were evaluated for three types of errors – Semantic errors, Phonological errors, and Fragments – using mixed-effects regression modeling with crossed random effects. Support for the Strength hypothesis was found for all three error types. Support for the Learning hypothesis was found for Semantic errors. All effects were due to error repair, not error detection. We discuss the theoretical and clinical implications of these novel findings.

The central thesis of this chapter is that data from aphasia provide a key link between behavioral studies of speech errors and neurocognitive models of language production. We describe a body of research that uses the interactive two-step model to characterize the cognitive machinery of lexical access and simulate aphasic speech error patterns in naming and repetition. The model incorporates a two-step lexical access process and a nonlexical process for accessing phonology directly from auditory input. It attributes the variety of aphasic error patterns to variation in model parameters. In a final step, we have used voxel-based lesion analysis to map the lesion correlates of error patterns and parameters in large numbers of individuals, thereby linking model processes and brain areas. This work complements and extends contemporary neurocognitive accounts of language and brain, demonstrating that aphasia research is as central to theory development today as it has been historically.

Meaningful speech, as exemplified in object naming, calls on knowledge of the mappings between word meanings and phonological forms. Phonological errors in naming (e.g. GHOST named as ‘goath’) are commonly seen in persisting post-stroke aphasia and are thought to signal impairment in retrieval of phonological form information. We performed a voxel-based lesion-symptom mapping analysis of 1718 phonological naming errors collected from 106 individuals with diverse profiles of aphasia. Voxels in which lesion status correlated with phonological error rates localized to dorsal stream areas, in keeping with classical and contemporary brain-language models. Within the dorsal stream, the critical voxels were concentrated in premotor cortex, pre- and postcentral gyri and supramarginal gyrus with minimal extension into auditory-related posterior temporal and temporo-parietal cortices. This challenges the popular notion that error-free phonological retrieval requires guidance from sensory traces stored in posterior auditory regions and points instead to sensory-motor processes located further anterior in the dorsal stream. In a separate analysis, we compared the lesion maps for phonological and semantic errors and determined that there was no spatial overlap, demonstrating that the brain segregates phonological and semantic retrieval operations in word production. * Abbreviations : FDR : false discovery rate MNI : Montreal Neurological Institute VLSM : voxel-based lesion-symptom mapping

Cognitive rehabilitation research is increasingly exploring errorless learning interventions, which prioritise the avoidance of errors during treatment. The errorless learning approach was originally developed for patients with severe anterograde amnesia, who were deemed to be at particular risk for error learning. Errorless learning has since been investigated in other memory-impaired populations (e.g., Alzheimer's disease) and acquired aphasia. In typical errorless training, target information is presented to the participant for study or immediate reproduction, a method that prevents participants from attempting to retrieve target information from long-term memory (i.e., retrieval practice). However, assuring error elimination by preventing difficult (and error-permitting) retrieval practice is a potential major drawback of the errorless approach. This review begins with discussion of research in the psychology of learning and memory that demonstrates the importance of difficult (and potentially errorful) retrieval practice for robust learning and prolonged performance gains. We then review treatment research comparing errorless and errorful methods in amnesia and aphasia, where only the latter provides (difficult) retrieval practice opportunities. In each clinical domain we find the advantage of the errorless approach is limited and may be offset by the therapeutic potential of retrieval practice. Gaps in current knowledge are identified that preclude strong conclusions regarding a preference for errorless treatments over methods that prioritise difficult retrieval practice. We offer recommendations for future research aimed at a strong test of errorless learning treatments, which involves direct comparison with methods where retrieval practice effects are maximised for long-term gains.

We explored the neural basis of reversible sentence comprehension in a large group of aphasic patients (n = 79). Voxel-based lesion symptom mapping revealed a significant association between damage in temporo-parietal cortex and impaired sentence comprehension. This association remained after we controlled for phonological working memory. We hypothesize that this region plays an important role in the thematic or what–where processing of sentences. In contrast, we detected weak or no association between reversible sentence comprehension and the ventrolateral pFC, which includes Broca's area, even for syntactically complex sentences. This casts doubt on theories that presuppose a critical role for this region in syntactic computations.

Several years ago, Eleanor Saffran, Nadine Martin, and the two of us began our collaborative project using aphasic speech errors to test production models that had been inspired by the errors of unimpaired speakers. At the time, though, one of us nearly balked upon seeing the data. Compared to everyday speech errors, transcripts of aphasic speech, even in controlled situations such as picture naming or word repetition, revealed an overwhelming amount of between- and even within-patient variation. To the seasoned CN researchers among us, this was no surprise. The researcher's art consists in finding ways to deal with the variability. The case series method is valuable because it allows the researcher to embrace, and ultimately, to tame the neuropsychological variability in service of testing theory. We are pleased that several distinguished CN researchers, some of whom have considerably more experience than we do with the method, generally agreed with the positive assessment of case series that we presented in Schwartz and Dell (2010). But commenters offered specific recommendations about the method, and pointed to lacunae in our paper. Is there is a right way to do a case series? In Schwartz and Dell (2010), we offered examples of case series studies in our work and in other research on topics that we had some familiarity with to show what one could do with the method, and made some recommendations about what one should do. The commenters augmented both the “could” and the “should” parts. Nickels, Howard, and Best remind us that case series could be used in treatment studies, and Shallice and Buiatti point to studies in which the selection of cases is based on anatomical rather than behavioural criteria. The studies they refer to seem to be clear examples of case series methodology. And they also remind us once more that it is hard to draw the boundaries between classic CN in which the goal is to draw inferences about normal cognition and the many other reasons for studying impaired cognition. A lot of the commentary concerned how one could (or should) treat individual differences in CN. Lambon-Ralph, Patterson, and Plaut consider the possibility that these differences can be due to pre-morbid factors explicable within the theory (e.g. the triangle theory of reading). They and Bub argue that appealing to this kind of individual variation had been “close to taboo” in the Aristotelian inspired single-subject approach to CN. We can agree with them that case series methods are well suited to the investigation of the contribution to performance of post-morbid individual differences (and pre-morbid differences, when data are available). Goldrick, however, tells us that appeals to individual differences are often too pat. When assumed to arise pre-morbidly, they usually lack pre-morbid supporting data. When assessed post-morbidly and simply attributed to differing degrees of damage

It is thought that semantic memory represents taxonomic information differently from thematic information. This study investigated the neural basis for the taxonomic-thematic distinction in a unique way. We gathered picture-naming errors from 86 individuals with poststroke language impairment (aphasia). Error rates were determined separately for taxonomic errors (“pear” in response to apple) and thematic errors (“worm” in response to apple), and their shared variance was regressed out of each measure. With the segmented lesions normalized to a common template, we carried out voxel-based lesion-symptom mapping on each error type separately. We found that taxonomic errors localized to the left anterior temporal lobe and thematic errors localized to the left temporoparietal junction. This is an indication that the contribution of these regions to semantic memory cleaves along taxonomic-thematic lines. Our findings show that a distinction long recognized in the psychological sciences is grounded in the structure and function of the human brain.

Patients with damage involving left ventrolateral prefrontal cortex (left VLPFC) often show syntactic deficits. They also show exaggerated interference effects during a variety of non-syntactic tasks, including picture naming and working memory. Conceivably, both deficits could arise from inadequate biasing of competitive interactions during language production. To test this hypothesis, we manipulated "positional" interference during multi-word naming by priming one of the nouns in the same or different position. Experimental case studies of four left VLPFC patients revealed that two of the patients showed exaggerated positional interference, greater number of errors, including omissions during multi-word production, increased production difficulty when the order of nouns did not match the predominant English pattern, as well as impaired comprehension of non-canonical reversible sentences. These results suggest that these two patients had an impairment in "selection for position". Different from the other two, their lesions included a subregion of frontal cortex (BA 44/6) that has been shown in neuroimaging studies to play a role in sequencing.

Semantic short-term memory (STM) deficits have been traditionally defined as an inability to maintain semantic representations over a delay (R. Martin, Shelton & Yaffee, 1994). Yet some patients with semantic STM deficits make numerous intrusions of items from previously presented lists, thus presenting an interesting paradox: Why should an inability to maintain semantic representations produce an increase in intrusions from earlier lists? In this study, we investigated the relationship between maintenance deficits and susceptibility to interference in a group of 20 aphasic patients characterized with weak semantic or weak phonological STM. Patients and matched control participants performed a modified item-recognition task designed to elicit semantic or phonological interference from list items located one, two, or three trials back (Hamilton & R. Martin, 2007). Controls demonstrated significant effects of interference in both versions of the task. Interference in patients was predicted by the type and severity of their STM deficit; that is, shorter semantic spans were associated with greater semantic interference and shorter phonological spans were associated with greater phonological interference. We interpret these results through a new perspective, the reactivation hypothesis, and we discuss their importance for accounts emphasizing the contribution of maintenance mechanisms for STM impairments in aphasia as well as susceptibility to interference.

Augmentative and alternative communication (AAC) technology has considerable potential to improve the lives of persons with aphasia (PWA). At the same time, there is growing awareness that AAC tech...

Analysis of error types provides useful information about the stages and processes involved in normal and aphasic word production. In picture naming, semantic errors (horse for goat) generally result from something having gone awry in lexical access such that the right concept was mapped to the wrong word. This study used the new lesion analysis technique known as voxel-based lesion-symptom mapping to investigate the locus of lesions that give rise to semantic naming errors. Semantic errors were obtained from 64 individuals with post-stroke aphasia, who also underwent high-resolution structural brain scans. Whole brain voxel-based lesion-symptom mapping was carried out to determine where lesion status predicted semantic error rate. The strongest associations were found in the left anterior to mid middle temporal gyrus. This area also showed strong and significant effects in further analyses that statistically controlled for deficits in pre-lexical, conceptualization processes that might have contributed to semantic error production. This study is the first to demonstrate a specific and necessary role for the left anterior temporal lobe in mapping concepts to words in production. We hypothesize that this role consists in the conveyance of fine-grained semantic distinctions to the lexical system. Our results line up with evidence from semantic dementia, the convergence zone framework and meta-analyses of neuroimaging studies on word production. At the same time, they cast doubt on the classical linkage of semantic error production to lesions in and around Wernicke's area.

BACKGROUND: SentenceShaper((R)) (SSR) is a computer program that is for speech what a word-processing program is for written text; it allows the user to record words and phrases, play them back, and manipulate them on-screen to build sentences and narratives. A recent study demonstrated that when listeners rated the informativeness of functional narratives produced by chronic aphasic speakers with and without the program they gave higher informativeness ratings to the language produced with the aid of the program (Bartlett, Fink, Schwartz, & Linebarger, 2007). Bartlett et al. (2007) also compared unaided (spontaneous) narratives produced before and after the aided version of the narrative was obtained. In a subset of comparisons, the sample created after was judged to be more informative; they called this "topic-specific carryover". AIMS: (1) To determine whether differences in informativeness that Bartlett et al.'s listeners perceived are also revealed by Correct Information Unit (CIU) analysis (Nicholas & Brookshire, 1993)-a well studied, objective method for measuring informativeness-and (2) to demonstrate the usefulness of CIU analysis for samples of this type. METHODS #ENTITYSTARTX00026; PROCEDURES: A modified version of the CIU analysis was applied to the speech samples obtained by Bartlett et al. (2007). They had asked five individuals with chronic aphasia to create functional narratives on two topics, under three conditions: Unaided ("U"), Aided ("SSR"), & Post-SSR Unaided ("Post-U"). Here, these samples were analysed for differences in % CIUs across conditions. Linear associations between listener judgements and CIU measures were evaluated with bivariate correlations and multiple regression analysis. OUTCOMES #ENTITYSTARTX00026; RESULTS: (1) The aided effect was confirmed: samples produced with SentenceShaper had higher % CIUs, in most cases exceeding 90%. (2) There was little CONCLUSIONS: That the percentage of CIUs was higher in SSR-aided samples than in unaided samples confirms the central finding in Bartlett et al. (2007), based on subjective judgements, and thus extends the evidence that aided effects from SentenceShaper are demonstrable across a range of measures, stimuli and participants (cf. Linebarger, Schwartz, Romania, Kohn, & Stephens, 2000). The data also attest to the effectiveness of the CIU analysis for quantifying differences in the informativeness of aphasic speech with and without SentenceShaper; and they support prior studies that have shown that CIU measures correlate with the informativeness ratings of unfamiliar listeners.

Errors in everyday activities pose significant consequences for individuals with mild cognitive deficits. However, there are few performance-based methods available to study action in these populations; the Coffee Challenge (CC) was designed for this purpose. Experiment 1 examined CC performance in healthy participants across 10 practice trials. Analyses showed evidence for routinization after 10 trials. In Experiment 2, CC performance was disrupted by dividing attention. Errors increased significantly, but performance was not qualitatively different from baseline. The results shed light on action impairments in patient populations and validate the CC as a promising new tool for future studies.

Lexical access in language production, and particularly pathologies of lexical access, are often investigated by examining errors in picture naming and word repetition. In this article, we test a computational approach to lexical access, the two-step interactive model, by examining whether the model can quantitatively predict the repetition-error patterns of 65 aphasic subjects from their naming errors. The model’s characterizations of the subjects’ naming errors were taken from the companion paper to this one (Schwartz, M. F., Dell, G. S., Martin, N., Gahl, S., & Sobel, P. (2006). A case-series test of the interactive two-step model of lexical access: evidence from picture naming. Journal of Memory and Language, 54 , 228–264), and their repetition was predicted from the model on the assumption that naming involves two error prone steps, word and phonological retrieval, whereas repetition only creates errors in the second of these steps. A version of the model in which lexical–semantic and lexical–phonological connections could be independently lesioned was generally successful in predicting repetition for the aphasics. An analysis of the few cases in which model predictions were inaccurate revealed the role of input phonology in the repetition task.

A novel multivariate lesion-symptom mapping (LSM) methodology was developed in this study. Lesion analysis is a classic model for studying brain functions. Using lesion data, focal brain-behavior associations have been widely assessed using the massive voxel-based lesion symptom mapping (VLSM) method. Assessing each voxel independently, VLSM suffers from low sensitivity after correcting for the enormous number of comparisons. It is also incapable for assessing a spatially distributed association pattern though the brain-behavior associations generally involve a collection of functionally related voxels. To solve these two outstanding problems, we carried out the first multivariate lesion symptom mapping (MLSM) in this study using support vector regression (SVR). In the so dubbed SVR-LSM, the symptom relation to the entire lesion map rather than each isolated voxel is modeled using a non-linear function, so the inter-voxel correlations are intrinsically considered, resulting in a potentially more sensitive way to examine lesion-symptom relationships. Evaluations using synthetic data and real data showed that SVR-LSM gained a much better performance (in terms of sensitivity and specificity) for detecting brain-behavior relations than VLSM. While the method was designed for lesion analysis, extending it to neuroimaging data will be straightforward.

Many facts about aphasic and nonaphasic naming are explained by models that use spreading activation to map from the semantics of a word to its phonology. The implemented model of picture naming discussed here achieves this by coupling interactive feedback with two selection steps. The model’s structure and default parameters were set up to match the normal naming profile; and aphasic naming is simulated by altering “lesionable” parameters away from default settings. Past studies within this framework have used different sets of lesionable parameters. Here, in the largest and most representative case-series ever modeled, we show the superiority of the version of the model that allows lesions to weaken semantic and/or phonological connections. Pairing this approach to lesions with the assumptions of interactivity and two-step selection equips the model to explain the wide variation in individual naming response profiles and key facts about lexical and sublexical errors.

Background: Aphasia can disrupt processing of semantic and/or phonological aspects of words and each of these domains involves multiple operations. Adequate assessment of word processing requires multiple measurements probing in each domain. This research was supported by grants from the National Institutes of Health to Moss Rehabilitation Research Institute (DC 00191‐21, PI: Myrna Schwartz) and to Temple University (DC01924‐11, PI: Nadine Martin). We thank Paula Sobel, Adelyn Brecher, Joe Marin, Jennifer Ayala, Kelly Bowes, Stephanie Tempest, and Lianne DiMarco for their help in collecting and organising the data reported here. We are especially grateful to the people who participated in these studies, and we thank them for their interest and support. Aims: This paper aims to facilitate accurate and comprehensive testing of the multiple operations involved in semantic and phonological processing of spoken words. Methods & Procedures: Normative data (means and standard deviations) from aphasic samples on ...

Nonaphasic speakers are known to take longer to name pictures when they are blocked by semantic category and repeated multiple times. We replicated this "semantic blocking effect" in older controls and showed that in aphasia, the effect is manifested in increased error rates when naming semantically homogeneous, compared to mixed blocks. We further showed that semantic blocking affects Broca's aphasics more than a matched group of NonBrocas, and that the effect increases with repetition of the blocked sets. Error analysis undermines the inhibition-based account of the blocking effect by showing that errors arise from competition among increasingly activated items within the homogeneous set. The consequent slowing of naming latencies is due at least in part to the intervention of a controlled selection mechanism, and the disruption of this mechanism in anterior aphasia accounts for the increase in error vulnerability.

Background : There are now numerous experimental studies demonstrating successful treatment of word retrieval deficits in aphasia. Technological advances allow us to implement many of these approaches on the computer and target the underlying impairment (e.g., in phonologically vs semantically based retrieval deficits). These computer-assisted treatments have the potential to facilitate the work of clinicians and, if geared towards independent or volunteer-assisted usage, extend the rehabilitation process beyond the period of formal therapy. Aims : Our aim is to review the benefits and limitations of computer-assisted treatment for word retrieval deficits, focusing on the lessons we have learned from a computerised therapy system, developed in our laboratory, which was designed to be used in the clinical setting, as well as by patients working independently. Contributions : We review relevant single and multiple case studies that use computer-assisted treatment programmes in various clinical and home sett...

A recent theory of lexical access in picture naming maintains that all nonword errors are generated during the retrieval of phonemic segments from the lexicon (Dell, Schwartz, Martin, Saffran,Gagnon, 1997b). This theory is challenged by "dual origin" theories that postulate a second, post-lexical mechanism, whose disruption gives rise to "phonemic paraphasias" bearing close resemblance to the target. We tested the dual origin theory in a corpus of 457 nonword errors drawn from 18 subjects with fluent aphasia. The corpus was divided into two parts, based on degree of phonological overlap between error and target, and these parts were separately examined for proposed diagnostic characteristics of the postlexical error mechanism: serial order effects across the word, sensitivity to target length, and insensitivity to target frequency. Results did not support the dual origin theory but were consistent with a single, lexical origin account in which segment retrieval operates from left to right, rather than in parallel. Findings from this study also shed new light on how individual differences in the severity of the retrieval deficit modulate the expression of phonological errors in relation to target characteristics.

Ideomotor apraxia (IM) is a disorder of skilled action characterized by spatiotemporal errors in pantomiming object use and in using objects. Recent evidence suggests that at least some patients with IM may exhibit particular deficits in forming hand configurations appropriate for object use. Sirigu et al. [Cortex 31 (1995) 41] reported an apraxic who positioned her hand inappropriately when attempting to use objects in accordance with stored knowledge of object-specific manipulation, but in reaching tasks could grasp the same objects appropriately in response to their structure. To this point, however, apraxics' ability to respond to functional and structural attributes of objects has not been empirically assessed. We investigated the hypothesis that patients with IM (n=9) due to left inferior parietal damage would be impaired in producing and recognizing hand postures associated with familiar objects, indicating deficient memorial representations for object-specific hand postures. In contrast, we predicted relatively unimpaired ability to produce and recognize appropriate hand postures with novel objects, indicating integrity of "on line" spatiomotor procedures coding hand position in response to object structure. Apraxics' performance was contrasted with 10 healthy controls and 8 brain-lesioned non-apraxics. Consistent with our predictions, the apraxics responded abnormally with familiar objects but normally in recognizing hand postures appropriate for novel objects. In addition, performance with objects calling for a prehensile response (pinch or clench) was superior to that with objects evoking a non-prehensile response (palm or poke). These data suggest degradation of inferior parietally-mediated representations of the precise hand postures associated with familiar objects. Furthermore, they are consistent with possible over-reliance upon dorsal system procedures for calculating precision and power grip in response to object structure.

Background: Computer-based rehabilitation programs are now available for patients' use at home and in the clinical setting, yet we have meagre outcome data associated with their usefulness under self- and/or clinician-guided conditions. Aims: We assess the benefits of a computer-delivered, hierarchical phonological cueing protocol (cued naming) under two conditions of instruction, (1) with full clinician guidance or (2) in partial independence. Methods & procedures: We employed a single-subject experimental design, which was replicated over six chronic aphasic subjects, three in each instruction condition. Subjects with deficits identified as primarily phonological in nature were administered a phonological treatment, utilising a computerised therapy program (MossTalk Words), under one of the two conditions. Outcomes & Results: Training-specific acquisition and maintenance was demonstrated in both conditions. Limited and variable generalisation patterns were noted. Conclusions: Chronic aphasic individuals...

The Naturalistic Action Test (NAT) measures everyday action impairment associated with damage to higher cortical functions. The tasks, procedures and scoring system were developed through extensive research. An earlier research instrument (the Multi-Level Action Test) was streamlined to create the NAT, which is scored for steps accomplished and for commission of a small set of recognised errors. This paper describes the NAT's psychometric properties, based on a study of 100 patients undergoing rehabilitation for TBI, left CVA, or right CVA (Part 1) and a follow-up study with approximately half of the original cohort (Part 2). Psychometric properties with respect to scoring reliability, internal consistency, and concurrent criterion validity were measured in Part 1 and found to be acceptable. Construct validity was assessed against a battery of attention tests; significant correlations were obtained between NAT scores and measures of arousal, visuospatial attention, and working memory. Part 2 showed that N...

This study analyses the naming performance of MP, a nonfluent aphasic speaker, and demonstrates that she has a context-sensitive naming deficit, which manifests in worse naming of a target set when multiple targets are depicted at once and a multiname utterance is prepared. Experiments 1 and 2 documented the effect in composite-picture descriptions, compared to standard naming. Experiment 3 documented it in the naming of picture lists of length 2 and 3, compared to 1; and Experiment 4 documented it in the naming of one of two pictured items, under conditions that encouraged preparation of both item names. Several alternative accounts are considered and an argument is made for a type of multiword naming deficit that has not been described before. The deficit involves interference at the lexeme stage of retrieval, arising when multiple lemmas are co-activated during the preparation of a multiword utterance.

Theories about the architecture of language processing differ with regard to whether verbal and nonverbal comprehension share a functional and neural substrate and how meaning extraction in comprehension relates to the ability to use meaning to drive verbal production. We (re-)evaluate data from 17 cognitive-linguistic performance measures of 99 participants with chronic aphasia using factor analysis to establish functional components and support vector regression-based lesion-symptom mapping to determine the neural correlates of deficits on these functional components. The results are highly consistent with our previous findings: production of semantic errors is behaviorally and neuroanatomically distinct from verbal and nonverbal comprehension. Semantic errors were most strongly associated with left ATL damage whereas deficits on tests of verbal and non-verbal semantic recognition were most strongly associated with damage to deep white matter underlying the frontal lobe at the confluence of multiple tracts, including the inferior fronto-occipital fasciculus, the uncinate fasciculus, and the anterior thalamic radiations. These results suggest that traditional views based on grey matter hub(s) for semantic processing are incomplete and that the role of white matter in semantic cognition has been underappreciated.

Studies of patients with acquired cognitive deficits following brain damage and studies using contemporary neuroimaging techniques form two distinct streams of research on the neural basis of cognition. In this study, we combine high-quality structural neuroimaging analysis techniques and extensive behavioural assessment of patients with persistent acquired language deficits to study the neural basis of language. Our results reveal two major divisions within the language system—meaning versus form and recognition versus production—and their instantiation in the brain. Phonological form deficits are associated with lesions in peri-Sylvian regions, whereas semantic production and recognition deficits are associated with damage to the left anterior temporal lobe and white matter connectivity with frontal cortex, respectively. These findings provide a novel synthesis of traditional and contemporary views of the cognitive and neural architecture of language processing, emphasizing dual routes for speech processing and convergence of white matter tracts for semantic control and/or integration. Contemporary neuroimaging techniques are enabling precise analysis of structure–function relations in the brain. This study combines large-scale structural neuroimaging and behavioural analyses in patients with acquired aphasia to elucidate the neural organization of spoken language processing.

Described here is an exploratory study designed to assess the feasibility of two new technologies for the treatment of aphasic sentence processing disorders: a computerised therapy programme incorporating natural language understanding (NLU), software which enables the computer to understand spoken utterances; and an augmentative communication system functioning primarily as a “processing prosthesis”, which allows patients to construct spoken sentences piecemeal and maintain elements already produced. Five agrammatic patients participated in a series of studies incorporating one or both of these technologies, and made language gains (ranging from modest to quite marked) following independent home use of the software. We hypothesise that the therapy and communication systems played complementary roles in this process, with the former training and/or priming specific grammatical structures and the latter providing the processing support necessary for these structures to be practised under normal conditions.