Aphasic Errors Research Articles

Precision of phonological errors in aphasia supports resource models of phonological working memory in language production

ABSTRACT Working memory (WM) is critical for many cognitive functions including language production. A key feature of WM is its capacity limitation. Two models have been proposed to account for such capacity limitation: slot models and resource models. In recent years, resource models have found support in both visual and auditory perception, but do they also extend to production? We investigate this by analyzing sublexical errors from four individuals with aphasia. Using tools from computational linguistics, we first define the concept of “precision” of sublexical errors. We then demonstrate that such precision decreases with increased working memory load, i.e., word length, as predicted by resource models. Finally, we rule out alternative accounts of this effect, such as articulatory simplification. These data provide the first evidence for the applicability of the resource model to production and further point to the generalizability of this account as a model of resource division in WM.

What semantic errors restricted to either speaking or writing in aphasia tell us about lemmas

ABSTRACT Theories about word production differ in whether they assume that lexical selection involves modality-specific representations or modality-neutral ones, called lemmas. The observation that semantic errors in aphasia may be restricted to either speaking or writing has long been taken to challenge lemma models (Hillis et al., 1999; Kemmerer, 2015, 2019). Whereas patients RGB, HW, and RR make semantic errors in speaking but not in writing, patient RCM exhibits the opposite dissociation. Here, using WEAVER++ simulations and a simple mathematical analysis, a model with lemmas is shown to account for the double dissociation observed in patients. In particular, the model captures the patterns of performance of the patients on vocal picture naming, written picture naming, auditory word comprehension, and writing to dictation, explaining 98% of the variance. The challenge is now for modality-specific models to account for the findings that the lemma model was designed to explain in the first place.

Sound Distortion Errors in Aphasia With Apraxia of Speech.

Purpose Loosely defined diagnostic criteria for acquired apraxia of speech (AOS) limit clinicians' ability to diagnose the disorder validly and reliably. The purpose of this study was to contribute to the development of more precise diagnostic guidelines by characterizing the frequency and quality of sound distortion errors in speakers with clinically diagnosed AOS. Method Audio-recorded motor speech evaluations from 24 speakers with AOS and aphasia were analyzed by trained listeners using a narrow phonetic transcription protocol that included 12 distortion categories. We calculated percentage of segments transcribed with phonemic error, distortion error, and a combination of phonemic and distortion error. Results Distortion frequency varied substantially across participants, distributing on a continuum from 5% to 22% of segments. The frequency of phonemic errors was significantly greater than the frequency of distortion errors, which, in turn, was greater than the frequency of distorted substitution errors. The most common distortion qualities were voicing ambiguity and segment lengthening, but over 40% of distortion errors were distributed across an assortment of tongue modifications. Conclusions The results replicated observations from previous studies of speakers with quantitatively defined AOS in a new sample of participants with clinically diagnosed AOS. Similar distortion qualities were observed across studies, offering focus for diagnosticians and guidance for operationalizing future measures. The broad performance continua we observed help explain why binary classification of the presence/absence of AOS can be challenging and indicate a need to develop quantitative norms.

The timing of spontaneous detection and repair of naming errors in aphasia

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.

EEG Error Prediction as a Solution for Combining the Advantages of Retrieval Practice and Errorless Learning.

Given the frequency of naming errors in aphasia, a common aim of speech and language rehabilitation is the improvement of naming. Based on evidence of significant word recall improvements in patients with memory impairments, errorless learning methods have been successfully applied to naming therapy in aphasia; however, other evidence suggests that although errorless learning can lead to better performance during treatment sessions, retrieval practice may be the key to lasting improvements. Task performance may vary with brain state (e.g., level of arousal, degree of task focus), and changes in brain state can be detected using EEG. With the ultimate goal of designing a system that monitors patient brain state in real time during therapy, we sought to determine whether errors could be predicted using spectral features obtained from an analysis of EEG. Thus, this study aimed to investigate the use of individual EEG responses to predict error production in aphasia. Eight participants with aphasia each completed 900 object-naming trials across three sessions while EEG was recorded and response accuracy scored for each trial. Analysis of the EEG response for seven of the eight participants showed significant correlations between EEG features and response accuracy (correct vs. incorrect) and error correction (correct, self-corrected, incorrect). Furthermore, upon combining the training data for the first two sessions, the model generalized to predict accuracy for performance in the third session for seven participants when accuracy was used as a predictor, and for five participants when error correction category was used as a predictor. With such ability to predict errors during therapy, it may be possible to use this information to intervene with errorless learning strategies only when necessary, thereby allowing patients to benefit from both the high within-session success of errorless learning as well as the longer-term improvements associated with retrieval practice.

Anosognosia and self-correction of naming errors in aphasia

ABSTRACTBackground: There has been comparatively little research into anosognosia for aphasia (a lack of awareness of acquired language deficits). Direct assessments of metacognitive awareness tend to rely on high levels of verbal competence and are difficult for people with aphasia to complete. Therefore, indirect measures of awareness have been considered, notably the person’s self-correction of his or her naming errors. Different mechanisms for self-correction based in comprehension or production skills have been proposed. In addition, in other areas of cognition, the relationships between direct and indirect measures and underlying forms of awareness have not been clearly established.Aims: The aims of this study were: (a) to investigate the relationship between a direct and an indirect measure of awareness of aphasia, (b) to examine the role of executive functioning in performance on both assessment types, and (c) to examine the relationship between these measures and underlying language comprehension and production skills.Methods & Procedures: A total of 48 people with aphasia participated, drawn from rehabilitation hospital caseloads. Participants were assessed on a language battery, a non-verbal test of executive function, a direct measure of awareness (ratings of difficulties), and had self-correction behaviour examined in a 40-item naming test.Outcomes & Results: There was a trend relationship between performance on the direct and indirect measures. Both related to overall severity of language impairment, with more severely impaired people being less aware of their difficulties. The two measures, however, dissociated with respect to single-word production and comprehension scores: the direct measure related to production and not comprehension, while the indirect measure related to comprehension and not production. Executive functioning related only to the direct measure of metacognitive awareness. Within production scores, the rate of correction success rather than pre-correction naming rate was associated with metacognitive awareness.Conclusions: This study revealed different underlying bases, in language processes and executive function, for two measures of anosognosia for aphasia. When used to assess awareness of deficits, direct and indirect methods should not be regarded as equivalent.

Stereotactic probability and variability of speech arrest and anomia sites during stimulation mapping of the language dominant hemisphere.

OBJECTIVE Functional mapping using direct cortical stimulation is the gold standard for the prevention of postoperative morbidity during resective surgery in dominant-hemisphere perisylvian regions. Its role is necessitated by the significant interindividual variability that has been observed for essential language sites. The aim in this study was to determine the statistical probability distribution of eliciting aphasic errors for any given stereotactically based cortical position in a patient cohort and to quantify the variability at each cortical site. METHODS Patients undergoing awake craniotomy for dominant-hemisphere primary brain tumor resection between 1999 and 2014 at the authors' institution were included in this study, which included counting and picture-naming tasks during dense speech mapping via cortical stimulation. Positive and negative stimulation sites were collected using an intraoperative frameless stereotactic neuronavigation system and were converted to Montreal Neurological Institute coordinates. Data were iteratively resampled to create mean and standard deviation probability maps for speech arrest and anomia. Patients were divided into groups with a "classic" or an "atypical" location of speech function, based on the resultant probability maps. Patient and clinical factors were then assessed for their association with an atypical location of speech sites by univariate and multivariate analysis. RESULTS Across 102 patients undergoing speech mapping, the overall probabilities of speech arrest and anomia were 0.51 and 0.33, respectively. Speech arrest was most likely to occur with stimulation of the posterior inferior frontal gyrus (maximum probability from individual bin = 0.025), and variance was highest in the dorsal premotor cortex and the posterior superior temporal gyrus. In contrast, stimulation within the posterior perisylvian cortex resulted in the maximum mean probability of anomia (maximum probability = 0.012), with large variance in the regions surrounding the posterior superior temporal gyrus, including the posterior middle temporal, angular, and supramarginal gyri. Patients with atypical speech localization were far more likely to have tumors in canonical Broca's or Wernicke's areas (OR 7.21, 95% CI 1.67-31.09, p < 0.01) or to have multilobar tumors (OR 12.58, 95% CI 2.22-71.42, p < 0.01), than were patients with classic speech localization. CONCLUSIONS This study provides statistical probability distribution maps for aphasic errors during cortical stimulation mapping in a patient cohort. Thus, the authors provide an expected probability of inducing speech arrest and anomia from specific 10-mm2 cortical bins in an individual patient. In addition, they highlight key regions of interindividual mapping variability that should be considered preoperatively. They believe these results will aid surgeons in their preoperative planning of eloquent cortex resection.

Simplicity and complexity in constructions

Linguistic complexity is usually approached in terms of markedness and branching structure, and psycholinguistic complexity in terms of frequency, sequential probability, and working memory load. However, predictions made on these bases appear to be inadequate to explain many patterns seen in aphasic speech. Psycholinguistic analyses of aphasic errors provide an empirical basis for describing lexical, morphological, and syntactic contributions to language complexity. We compare the predictions made by existing descriptions of complexity to aphasic error data as reported in cross‐linguistic studies. A construction‐based approach may be able to unify the patterns seen across lexicon, morphology and syntax.

Gender Agreement: a psycholinguistic and aphasia case study.

Gender Agreement: a psycholinguistic and aphasia case study.

Facilitatory and interfering effects of neighbourhood density on speech production: Evidence from aphasic errors

In a system where tens of thousands of words are made up of a limited number of phonemes, many words are bound to sound alike. This similarity of the words in the lexicon as characterized by phonological neighbourhood density (PhND) has been shown to affect speed and accuracy of word comprehension and production. Whereas there is a consensus about the interfering nature of neighbourhood effects in comprehension, the language production literature offers a more contradictory picture with mainly facilitatory but also interfering effects reported on word production. Here we report both of these two types of effects in the same study. Multiple regression mixed models analyses were conducted on PhND effects on errors produced in a naming task by a group of 21 participants with aphasia. These participants produced more formal errors (interfering effect) for words in dense phonological neighbourhoods, but produced fewer nonwords and semantic errors (a facilitatory effect) with increasing density. In order to investigate the nature of these opposite effects of PhND, we further analysed a subset of formal errors and nonword errors by distinguishing errors differing on a single phoneme from the target (corresponding to the definition of phonological neighbours) from those differing on two or more phonemes. This analysis confirmed that only formal errors that were phonological neighbours of the target increased in dense neighbourhoods, while all other errors decreased. Based on additional observations favouring a lexical origin of these formal errors (they exceeded the probability of producing a real-word error by chance, were of a higher frequency, and preserved the grammatical category of the targets), we suggest that the interfering effect of PhND is due to competition between lexical neighbours and target words in dense neighbourhoods.

Are Number Words Fundamentally Different? A Qualitative Analysis of Aphasic Errors in Word and Number Word Production

A number of previous studies reported dissociations between the processing of number words and other words and reasoned that there are fundamentally different mental representations and/or processing strategies related to these types of words. Messina et al. reported the performance of Italian aphasic patients with words and number words in different tasks [1]. In line with previous studies, they found that lexical errors formed the dominant error type in number words, whereas phonological errors were the most frequent error type in other words. Messina et al. [1] concluded that speech production processes differ categorically between number words and other words, leading to qualitatively different error patterns in language breakdown. The present study examined error types in number words and other words in a sample of 15 German patients with aphasia using the same tasks as Messina et al. [1]. Performance in reading and repeating number words and other words was analysed. In general, we replicated the dissociation of error types between number words and other words reported by Messina et al. [1] and others. However, in contrast to previous assumptions this dissociation was not categorical but rather gradual. We suggest that psycholinguistic stimulus properties (such as number of repetitions per morpheme) and type of task influenced error types in a gradual fashion. Keywords: Aphasia, number word processing, transcoding, phonological errors, lexical errors, dissociation. Read more →

Gender Errors in Aphasia Reveal a Projection for Contextually Dependent Gender in Syntax

Gender Errors in Aphasia Reveal a Projection for Contextually Dependent Gender in Syntax

Similarities and Differences Between Perseverative and Non-Perseverative Errors in Aphasia: Theoretical and Clinical Implications

Researchers have learned much about the cognitive organization of the language system by studying speech errors made by speakers with and without aphasia. Some aspects of errors made in language production reflect linguistic properties of language (e.g., linguistic similarities between an intended word and the word that was produced in error). Other aspects reflect processes that enable production of language (e.g., substitutions or sequencing errors). A particularly intriguing class of error is perseveration, the unintended retrieval of words or sounds after they have been recently produced. Although the occurrence of perseverations is influenced by both linguistic and processing aspects of language production, these errors have been particularly instructive about the latter aspect. Martin and Dell (2007) proposed that word and sound perseverations result from the same mechanisms as non-perseverative substitutions: slowed activation of the intended utterance and linguistic similarity between the target and error. They differ from non-perseverative substitutions in their probability of occurrence, which is increased by residual activation following their recent production. In this article, I will review this account of perseverations and discuss its implications for treatment approaches to reduce perseverations.

SIG 2 Perspectives Vol. 21, No 4, December 2011

SIG 2 Perspectives Vol. 21, No 4, December 2011

On the Nature of Speech Errors in Aphasia: Acoustic Analysis of the Speech Output of 8 Native Speakers of Spanish with Aphasia

On the Nature of Speech Errors in Aphasia: Acoustic Analysis of the Speech Output of 8 Native Speakers of Spanish with Aphasia

Effects of syllable structure in aphasic errors: Implications for a new model of speech production

Current models of word production assume that words are stored as linear sequences of phonemes which are structured into syllables only at the moment of production. This is because syllable structure is always recoverable from the sequence of phonemes. In contrast, we present theoretical and empirical evidence that syllable structure is lexically represented. Storing syllable structure would have the advantage of making representations more stable and resistant to damage. On the other hand, re-syllabifications affect only a minimal part of phonological representations and occur only in some languages and depending on speech register. Evidence for these claims comes from analyses of aphasic errors which not only respect phonotactic constraints, but also avoid transformations which move the syllabic structure of the word further away from the original structure, even when equating for segmental complexity. This is true across tasks, types of errors, and, crucially, types of patients. The same syllabic effects are shown by apraxic patients and by phonological patients who have more central difficulties in retrieving phonological representations. If syllable structure was only computed after phoneme retrieval, it would have no way to influence the errors of phonological patients. Our results have implications for psycholinguistic and computational models of language as well as for clinical and educational practices.

Support for anterior temporal involvement in semantic error production in aphasia: New evidence from VLSM

Semantic errors in aphasia (e.g., naming a horse as “dog”) frequently arise from faulty mapping of concepts onto lexical items. A recent study by our group used voxel-based lesion-symptom mapping (VLSM) methods with 64 patients with chronic aphasia to identify voxels that carry an association with semantic errors. The strongest associations were found in the left anterior temporal lobe (L-ATL), in the mid- to anterior MTG region. The absence of findings in Wernicke’s area was surprising, as were indications that ATL voxels made an essential contribution to the post-semantic stage of lexical access. In this follow-up study, we sought to validate these results by re-defining semantic errors in a manner that was less theory dependent and more consistent with prior lesion studies. As this change also increased the robustness of the dependent variable, it made it possible to perform additional statistical analyses that further refined the interpretation. The results strengthen the evidence for a causal relationship between ATL damage and lexically-based semantic errors in naming and lend confidence to the conclusion that chronic lesions in Wernicke’s area are not causally implicated in semantic error production.

Origin of phoneme substitution and phoneme movement errors in aphasia

Despite a general consensus about the lexical-phonological origin of phonological errors, a debate persists concerning a single or multiple origins of such errors. In particular, a similar post-lexical origin has been attributed to milder phonological paraphasias, such as phoneme substitution errors, and to normal slips of the tongue. However, most slips of the tongue have a contextual origin, while most phonological paraphasias are not contextual errors. Here we explore the possibility that even at post-lexical encoding levels different errors are generated by distinct processes. We take advantage of the production of an unusual proportion of within-word phoneme movement errors in a patient with conduction aphasia (SJ) and tackle the question of their origin in comparison to phoneme substitution errors. Error properties relative to phoneme substitution and phoneme movement errors produced by SJ were analysed and compared with those of a second patient (GF) who produced a similar proportion of substitution errors but no movement errors. Very similar profiles between the two patients emerged on substitution errors, while phoneme movement errors displayed different properties. The observation that substitution and movement errors are not affected by the same factors favours a different origin of these errors. The sub-lexical frequency and similarity effects and the lexical bias in substitution errors indicate an interaction between multiple encoding levels during the production of these errors; by contrast, movement errors seem related to a different and independent process bearing no interaction with other levels of representation.

Cortical mapping of naming errors in aphasia

Persons with aphasia vary greatly with regard to clinical profile; yet, they all share one common feature-anomia-an impairment in naming common objects. Previous research has demonstrated that particular naming errors are associated with specific left hemisphere lesions. However, we know very little about the cortical activity in the preserved brain areas that is associated with aphasic speech errors. Utilizing functional magnetic resonance imaging (fMRI), we show for the first time that specific speech errors are associated with common cortical activity in different types and severities of aphasia. Specifically, productions of phonemic errors recruited the left posterior perilesional occipital and temporal lobe areas. A similar pattern of activity was associated with semantic errors, albeit in the right hemisphere. This study does not discount variability in cortical activity following left hemisphere stroke; rather, it highlights commonalities in brain modulation in a population of patients with a common diagnosis but vastly different clinical profiles.

Sublexical units in aphasic jargon and in the standard language: Comparative analyses of neologisms in connected speech

Background: It is a well‐documented finding that phonemic speech errors in aphasia reflect certain characteristics of their intended targets. However, only few studies have investigated spontaneous speech productions of jargon‐aphasic patients, in which lexical targets may be completely unrecognisable (abstruse phonemic neologisms). There is some evidence that these neologisms correspond to the standard language concerning phonemic content and structure. Aims: The present study further explores similarities of aphasic neologisms and the standard language, to contribute to the discussion about the origin of non‐target‐related errors in jargon aphasia. It investigates whether similarities at the phoneme level can be confirmed even in connected, severely jargonised speech that does not allow identification of lexical targets. Moreover, it raises the question whether other sublexical units like syllables contribute to the formation of phonemic neologisms. Methods & Procedures: Neologisms in spontaneous speech of a German‐speaking jargon‐aphasic patient were compared to the standard language concerning phoneme and syllable inventory, structural aspects, and distributional frequencies of sublexical measures. Data of the standard language were derived from meta‐analyses of a German phonological word form database. Outcomes & Results: A strong relatedness to the standard language was demonstrated for the aphasic neologisms in connected speech. Similarities regarded phoneme inventory, phonotactics, and phoneme frequency distributions. The patient data point to a preferred use of high‐frequency phonemes and syllables in neologisms. In addition, a similar distribution of syllable frequencies and structures was observed in the neologisms and in standard German. Results indicate that syllable frequency serves as a predictor for the neologisms' distributional frequencies. Conclusions: The present study indicated that phonemic neologisms with no or weak evidence for a lexical origin still conformed to the phonological characteristics of the standard language, suggesting undisturbed segmental phonological processing. With respect to processing levels in speech production, results specifically pointed to a prominent role of syllabic units. The present findings are compatible with the assumption that syllabic representations, like structural information of syllables, are constrained in neologism formation.