Lexical competition effects in aphasia: deactivation of lexical candidates in spoken word processing

Rational adaptation in word production: Strong conceptual ability reduces the effect of lexical impairments on verb retrieval in aphasia

Language users rely on both linguistic and conceptual processing abilities to efficiently comprehend or produce language. According to the principle of rational adaptation, the degree to which a cognitive system relies on one process vs. another can change under different conditions or disease states with the goal of optimizing behavior. In this study, we investigated rational adaptation in reliance on linguistic versus conceptual processing in aphasia, an acquired disorder of language. In individuals living with aphasia, verb-retrieval impairments are a pervasive deficit that negatively impacts communicative function. As such, we examined evidence of adaptation in verb production, using parallel measures to index impairment in two of verb naming's critical subcomponents: conceptual and linguistic processing. These component processes were evaluated using a standardized assessment battery designed to contrast non-linguistic (picture input) and linguistic (word input) tasks of conceptual action knowledge. The results indicate that non-linguistic conceptual action processing can be impaired in people with aphasia and contributes to verb-retrieval impairments. Furthermore, relatively unimpaired conceptual action processing can ameliorate the influence of linguistic processing deficits on verb-retrieval impairments. These findings are consistent with rational adaptation accounts, indicating that conceptual processing plays a key role in language function and can be leveraged in rehabilitation to improve verb retrieval in adults with chronic aphasia.

Telepractice in speech-language pathology: Assessing remote speech discrimination

PURPOSE

To evaluate adult remote performance in speech discrimination on the Temple Assessment of Language and Short-term Memory in Aphasia (TALSA), and to compare to remote performance in NU-6 word repetition and participant ratings of self-perceived hearing ability obtained via remote session.

METHOD

Sixty older adults completed TALSA speech discrimination of concrete, low frequency words and of non-words via telephone. Remote repetition of words controlled for sound frequency was assessed using the Northwestern University (NU-6) word lists administered in live voice and recorded voice conditions. Forty-six of the participants completed questionnaires about their hearing via Zoom videoconference.

RESULTS

Mean performance in TALSA speech discrimination for words was similar to performance in NU-6 word repetition. Word repetition of NU-6 lists did not differ significantly for live voice versus recorded voice conditions. TALSA non-word speech discrimination was significantly worse than TALSA speech discrimination for words and was associated with age and self-reported hearing ability.

CONCLUSIONS

TALSA speech discrimination can be administered remotely to evaluate potential perceptual influences on auditory comprehension. In remote assessment, participants demonstrated the expected pattern of more accurate speech discrimination for word stimuli than for non-words. The non-word TALSA condition may be particularly useful for detecting speech perception impairment, both in face-to-face and telepractice sessions. Similar performance of participants in both live voice and recorded conditions of the NU-6 word lists suggests that recordings used in SLP receptive language or memory assessment, including the TALSA, need not be abandoned in favor of live voice to support audition during telepractice.

The effect of time on lexical and syntactic processing in aphasia

Processing deficits at the lexical level, such as delayed and reduced lexical activation, have been theorized as the source of breakdowns in syntactic operations and thus contribute to sentence comprehension deficits in individuals with aphasia (IWA). In the current study, we investigate the relationship between lexical and syntactic processing in object-relative sentences using eye-tracking while listening in IWA. We explore whether manipulating the time available to process a critical lexical item (the direct-object noun) when it is initially heard in a sentence has an immediate effect on lexical access as well as a downstream effect on syntactic processing. To achieve this aim, we use novel temporal manipulations to provide additional time for lexical processing to occur. In addition to exploring these temporal effects in IWA, we also seek to understand the effect that additional time has on sentence processing in neurotypical age-matched adults (AMC). We predict that the temporal manipulations designed to provide increased processing time for critical lexical items will 1) enhance lexical processing of the target noun, 2) facilitate syntactic integration, and 3) improve sentence comprehension for both IWA and AMC. We demonstrate that strengthening lexical processing via the addition of time can affect lexical processing and facilitate syntactic retrieval of the target noun and lead to enhanced interference resolution in both unimpaired and impaired systems. In aphasia, additional time can mitigate impairments in spreading activation thereby improving lexical access and reducing interference during downstream dependency linking. However, individuals with aphasia may require longer additions of time to fully realize these benefits.

Sentence Recall in Latent and Anomic Aphasia: An Exploratory Study of Semantics and Syntax

We investigated whether semantic plausibility and syntactic complexity affect immediate sentence recall in people with latent and anomic aphasia. To date, these factors have not been explored in these types of aphasia. As with previous studies of sentence recall, we measured accuracy of verbatim recall and uniquely real-time speech measures. The results showed that accuracy did not distinguish performance between latent aphasia and neurotypical controls. However, some of the real-time speech measures distinguished performance between people with latent aphasia and neurotypical controls. There was some evidence, though not pervasive, that semantic plausibility and syntactic complexity influenced recall performance. There were no interactions between semantic plausibility and syntactic complexity. The speed of preparation of responses was slower in latent aphasia than controls; it was also slower in anomic aphasia than both latent and control groups. It appears that processing speed as indexed by temporal speech measures may be differentially compromised in latent and anomic aphasia. However, semantic plausibility and syntactic complexity did not show clear patterns of performance among the groups. Notwithstanding the absence of interactions, we advance an explanation based on conceptual short-term memory as to why semantically implausible sentences are typically more erroneous and possibly also slower in recall.

Primed to cue

The behavioral effects of lexical priming are well studied in the cognitive sciences. Clinical use of the term and widespread implementation of priming based behavioral interventions has remained limited. This is despite the fact that response-contingent cueing, a behavioral intervention technique used during many cognitive-linguistic interventions, is grounded in theories of priming research. The aim of this manuscript is to connect behavioral performance changes observed following priming with those noted following cueing, providing a theoretical rationale for the therapeutic use of both priming and cueing in language and cognitive interventions. In this review, we establish a conceptual basis for how both primes and cues serve to pre-engage the neural system by triggering the retrieval of linked conceptual knowledge, resulting in faster and more accurate responses. Differences between the two (primes and cues) have been linked to timing and conscious intentional engagement, though these distinctions are often task dependent. Additionally, this paper will provide evidence of the clinical utility of priming. Studies of priming in adults with acquired brain injuries are discussed and clinical interventions based on theories of priming are examined. Furthermore, the present work will briefly detail the inhibitory effects of priming to aid clinicians and researchers in deciding how to pair primes and cues with intended retrieval targets. In summation, the present work is intended to bridge two related fields providing both theoretical and clinical insight with respect to the use of primes and cues.

Varieties of semantic 'access' deficit in Wernicke's aphasia and semantic aphasia

Comprehension deficits are common in stroke aphasia, including in cases with (i) semantic aphasia, characterized by poor executive control of semantic processing across verbal and non-verbal modalities; and (ii) Wernicke's aphasia, associated with poor auditory-verbal comprehension and repetition, plus fluent speech with jargon. However, the varieties of these comprehension problems, and their underlying causes, are not well understood. Both patient groups exhibit some type of semantic 'access' deficit, as opposed to the 'storage' deficits observed in semantic dementia. Nevertheless, existing descriptions suggest that these patients might have different varieties of 'access' impairment-related to difficulty resolving competition (in semantic aphasia) versus initial activation of concepts from sensory inputs (in Wernicke's aphasia). We used a case series design to compare patients with Wernicke's aphasia and those with semantic aphasia on Warrington's paradigmatic assessment of semantic 'access' deficits. In these verbal and non-verbal matching tasks, a small set of semantically-related items are repeatedly presented over several cycles so that the target on one trial becomes a distractor on another (building up interference and eliciting semantic 'blocking' effects). Patients with Wernicke's aphasia and semantic aphasia were distinguished according to lesion location in the temporal cortex, but in each group, some individuals had additional prefrontal damage. Both of these aspects of lesion variability-one that mapped onto classical 'syndromes' and one that did not-predicted aspects of the semantic 'access' deficit. Both semantic aphasia and Wernicke's aphasia cases showed multimodal semantic impairment, although as expected, the Wernicke's aphasia group showed greater deficits on auditory-verbal than picture judgements. Distribution of damage in the temporal lobe was crucial for predicting the initially 'beneficial' effects of stimulus repetition: cases with Wernicke's aphasia showed initial improvement with repetition of words and pictures, while in semantic aphasia, semantic access was initially good but declined in the face of competition from previous targets. Prefrontal damage predicted the 'harmful' effects of repetition: the ability to reselect both word and picture targets in the face of mounting competition was linked to left prefrontal damage in both groups. Therefore, patients with semantic aphasia and Wernicke's aphasia have partially distinct impairment of semantic 'access' but, across these syndromes, prefrontal lesions produce declining comprehension with repetition in both verbal and non-verbal tasks.

Processing lexical ambiguity in sentential context: Eye-tracking data from brain-damaged and non-brain-damaged individuals

The purpose of the present study was to identify general and syndrome-specific deficits in the lexical processing of individuals with non-fluent and fluent aphasia compared to individuals without cognitive, neurological or language impairments. The time course of lexical access, as well as lexical selection and integration was studied using a visual-world paradigm in three groups of Russian speakers: 36 individuals in the control group, 15 individuals with non-fluent aphasia and eight individuals with fluent aphasia. Participants listened to temporarily ambiguous sentences wherein the context biased the interpretation of an ambiguous word toward one of its two meanings. In half of the experimental sentences, a reanalysis was needed upon encountering the disambiguating phrase. The effect of the length of the intervening material between the ambiguous word and the disambiguation point was additionally monitored. All groups of participants showed intact lexical access under slowed speech rate, but non-fluent participants experienced difficulties with timely activation of multiple referents. At later stages of lexical processing, they additionally demonstrated a specific impairment of reanalysis. The deficit in participants with fluent aphasia was not focalized at any specific stage of lexical processing. Rather, the breakdown of lexical processes in fluent aphasia was likely related to difficulties with the inhibition of irrelevant lexical activation, which is further supported by the finding that increased phonological distance between the ambiguous word and ambiguity resolution was influential to the offline performance in this group.

Effects of verb meaning on lexical integration in agrammatic aphasia: Evidence from eyetracking

Relatively little is known about the time course of access to the lexical representations of verbs in agrammatic aphasia and its effects on the prediction and integration of the verb's arguments. The present study used visual-world eyetracking to test whether verb meaning can be used by agrammatic aphasic individuals to predict and facilitate the integration of a subsequent noun argument. Nine adults with agrammatic aphasia and ten age-matched controls participated in the study. In Experiment 1, participants viewed arrays of four objects (e.g., jar, plate, stick, pencil) while listening to sentences containing either a restrictive verb that was semantically compatible only with the target object or an unrestrictive verb compatible with all four objects (e.g., Susan will open/break the jar). For both participant groups, the restrictive condition elicited more fixations to the target object immediately after the verb. Experiment 2 differed from Experiment 1 in that the auditory sentences presented were incomplete (e.g., Susan will open/break the…). For controls, restrictive verbs elicited more target fixations immediately after the verb; however, the effects of verb type were noted downstream from the verb for the aphasic listeners. The results suggest that individuals with agrammatic aphasia have preserved ability to use verb information to facilitate integration of overt arguments, but prediction of upcoming arguments is impaired. Impaired lexical-semantic prediction processes may be caused by damage to the left inferior frontal gyrus, which has been argued to support higher-level lexical processes.

Phonological facilitation of object naming in agrammatic and logopenic primary progressive aphasia (PPA)

Phonological processing deficits are characteristic of both the agrammatic and logopenic subtypes of primary progressive aphasia (PPA-G and PPA-L). However, it is an open question which substages of phonological processing (i.e., phonological word form retrieval, phonological encoding) are impaired in these subtypes of PPA, as well as how phonological processing deficits contribute to anomia. In the present study, participants with PPA-G (n = 7), participants with PPA-L (n = 7), and unimpaired controls (n = 17) named objects as interfering written words (phonologically related/unrelated) were presented at different stimulus onset asynchronies (SOAs) of 0, +100, +300, and +500 ms. Phonological facilitation (PF) effects (faster naming times with phonologically related interfering words) were found for the controls and PPA-L group only at SOA = 0 and +100 ms. However, the PPA-G group exhibited protracted PF effects (PF at SOA = 0, +100, and +300 ms). These results may reflect deficits in phonological encoding in PPA-G, but not in PPA-L, supporting the neuropsychological reality of this substage of phonological processing and the distinction between these two PPA subtypes.

Semantic interference during object naming in agrammatic and logopenic primary progressive aphasia (PPA)

This study examined the time course of object naming in 21 individuals with primary progressive aphasia (PPA) (8 agrammatic (PPA-G); 13 logopenic (PPA-L)) and healthy age-matched speakers (n=17) using a semantic interference paradigm with related and unrelated interfering stimuli presented at stimulus onset asynchronies (SOAs) of -1000, -500, -100 and 0 ms. Results showed semantic interference (SI) (i.e. significantly slower RTs in related compared to unrelated conditions) for all groups at -500, -100 and 0 ms, indicating timely spreading activation to semantic competitors. However, both PPA groups showed a greater magnitude of SI than normal across SOAs. The PPA-L group and six PPA-G participants also evinced SI at -1000 ms, suggesting an abnormal time course of semantic interference resolution, and concomitant left hemisphere cortical atrophy in brain regions associated with semantic processing. These subtle semantic mapping impairments in non-semantic variants of PPA may contribute to the anomia of these patients.

Engagement of temporal lobe regions predicts response to educational interventions in adolescent struggling readers

Brain activation profiles obtained using magnetoencephalography were compared between middle-school students experiencing reading difficulties and non-reading-impaired students during performance of a continuous printed word recognition task. Struggling readers underwent small-group remedial instruction, and students who showed significant gains in word reading efficiency at a one-year follow-up assessment were classified as Adequate Responders whereas those not demonstrating such gains as Inadequate Responders. At baseline, compared to Inadequate Responders, the activation profiles of Adequate Responders featured increased activity in the left middle, superior temporal, and ventral occipitotemporal regions, as well as in the right mesial temporal cortex. The degree of activity in these regions was a significant predictor of improvement in word reading efficiency beyond the prediction afforded by baseline reading accuracy or fluency measures. The engagement of brain areas that typically serve as key components of the brain circuit for reading may be an important factor in predicting response to intervention in older students who experience reading difficulties.

The timing and strength of regional brain activation associated with word recognition in children with reading difficulties

The study investigates the relative degree and timing of cortical activation across parietal, temporal, and frontal regions during performance of a continuous visual-word recognition task in children who experience reading difficulties (N = 44, RD) and typical readers (N = 40, NI). Minimum norm estimates of regional neurophysiological activity were obtained from magnetoencephalographic recordings. Children with RD showed bilaterally reduced neurophysiological activity in the superior and middle temporal gyri, and increased activity in rostral middle frontal and ventral occipitotemporal cortices, bilaterally. The temporal profile of activity in the RD group, featured near-simultaneous activity peaks in temporal, inferior parietal, and prefrontal regions, in contrast to a clear temporal progression of activity among these areas in the NI group. These results replicate and extend previous MEG and fMRI results demonstrating atypical, latency-dependent attributes of the brain circuit involved in word reading in children with reading difficulties.

Theories of spoken word recognition deficits in aphasia: evidence from eye-tracking and computational modeling

We used eye-tracking to investigate lexical processing in aphasic participants by examining the fixation time course for rhyme (e.g., carrot-parrot) and cohort (e.g., beaker-beetle) competitors. Broca's aphasic participants exhibited larger rhyme competition effects than age-matched controls. A re-analysis of previously reported data (Yee, Blumstein, & Sedivy, 2008) confirmed that Wernicke's aphasic participants exhibited larger cohort competition effects. Individual-level analyses revealed a negative correlation between rhyme and cohort competition effect size across both groups of aphasic participants. Computational model simulations were performed to examine which of several accounts of lexical processing deficits in aphasia might account for the observed effects. Simulation results revealed that slower deactivation of lexical competitors could account for increased cohort competition in Wernicke's aphasic participants; auditory perceptual impairment could account for increased rhyme competition in Broca's aphasic participants; and a perturbation of a parameter controlling selection among competing alternatives could account for both patterns, as well as the correlation between the effects. In light of these simulation results, we discuss theoretical accounts that have the potential to explain the dynamics of spoken word recognition in aphasia and the possible roles of anterior and posterior brain regions in lexical processing and cognitive control.

The role of Broca's area in regular past-tense morphology: an event-related potential study

It has been suggested that damage to anterior regions of the left hemisphere results in a dissociation in the perception and lexical activation of past-tense forms. Specifically, in a lexical-decision task in which past-tense primes immediately precede present-tense targets, such patients demonstrate significant priming for irregular verbs (spoke-speak), but, unlike control participants, fail to do so for regular verbs (looked-look). Here, this behavioral dissociation was first confirmed in a group of eleven patients with damage to the pars opercularis (BA 44) and pars triangularis (BA 45) of the left inferior frontal gyrus (i.e., Broca's area). Two conditions containing word-onset orthographic-phonological overlap (bead-bee, barge-bar) demonstrated that the disrupted regular-verb priming was accompanied by, and covaried with, disrupted ortho-phonological priming, regardless of whether prime stimuli contained the regular inflectional rhyme pattern. Further, the dissociation between impaired regular-verb and preserved irregular-verb priming was shown to be continuous rather than categorical; priming for weak-irregular verbs (spent-spend) was intermediate in size between that of regular verbs and strong verbs. Such continuous dissociations grounded in ortho-phonological relationships between present- and past-tense forms are predicted by single-system, connectionist approaches to inflectional morphology and not predicted by current dual-system, rule-based models. Event-related potential data demonstrated that N400 priming effects were intact for both regular and irregular verbs, suggesting that the absence of significant regular-verb priming in the response time data did not result from a disruption of lexical access, and may have stemmed instead from post-lexical events such as covert articulation, segmentation strategies, and/or cognitive control.

The use of the picture-word interference paradigm to examine naming abilities in aphasic individuals

BACKGROUND

Although naming deficits are well documented in aphasia, on-line measures of naming processes have been little investigated. The use of on-line measures may offer further insight into the nature of aphasic naming deficits that would otherwise be difficult to interpret when using off-line measures.

AIMS

The temporal activation of semantic and phonological processes was tracked in older normal control and aphasic individuals using a picture-word interference paradigm. The purpose of the study was to examine how word interference results can augment and/or corroborate standard language testing in the aphasic group, as well as to examine temporal patterns of activation in the aphasic group when compared to a normal control group.

METHODS & PROCEDURES

A total of 20 older normal individuals and 11 aphasic individuals participated. Detailed measures of each aphasic individual's language and naming skills were obtained. A visual picture-word interference paradigm was used in which the words bore either a semantic, phonological, or no relationship to 25 pictures. These competitor words were presented at stimulus onset asynchronies of -300 ms, +300 ms, and 0 ms.

OUTCOMES & RESULTS

Analyses of naming RTs in both groups revealed significant early semantic interference effects, mid-semantic interference effects, and mid-phonological facilitation effects. A matched control-aphasic group comparison revealed no differences in the temporal activation of effects during the course of naming. Partial support for this RT pattern was found in the aphasic naming error pattern. The aphasic group also demonstrated greater SIEs and PFEs compared to the matched control group, which indicated disruptions of the phonological processing stage. Analyses of behavioural performances of the aphasic group corroborated this finding.

CONCLUSIONS

The aphasic naming RTs results were unexpected given the results from the priming literature, which has supported the idea of slowed or reduced patterns of activation in aphasic individuals. However, analyses of naming RTs also confirmed the behavioural finding of a disruption surrounding phonological processes; thus, the analyses of naming latencies offers another potential means of pinpointing breakdowns of lexical access in individuals with aphasia.

Auditory word recognition: evidence from aphasia and functional neuroimaging

This review examines the neural systems underlying auditory word recognition processes using both lesion and functional neuroimaging studies. Focus is on the influence of the sound properties of language (its phonetic as well as its phonological properties) in the service of identifying a particular word or the conceptual/meaning associated with that word. Results indicate that auditory word recognition recruits a neural system in which information is passed through the network in what appears to be functionally distinct stages - acoustic-phonetic analysis in temporal areas, mapping of sound structure to the lexicon, accessing a lexical candidate and its associated lexical-semantic network in temporo-parietal areas, and lexical selection in frontal areas. Information cascades throughout the network as shown by the influence of 'goodness' of fit and phonological/lexical competition on modulation of activation in both posterior areas including the superior temporal gyrus and supramarginal gyrus and in frontal areas including the inferior frontal gyrus.

Neighbourhood density effects in auditory non-word processing in aphasic listeners

This study investigates neighbourhood density effects on lexical decision performance (both accuracy and response times) of aphasic patients. Given earlier results on lexical activation and deactivation in Broca's and Wernicke's aphasia, the prediction was that smaller neighbourhood density effects would be found for Broca's aphasic patients, compared to age-matched non-brain-damaged control participants, whereas enlarged density effects were expected for Wernicke's aphasic patients. The results showed density effects for all three groups of listeners, and overall differences in performance between groups, but no significant interaction between neighbourhood density and listener group. Several factors are discussed to account for the present results.

Lexical-semantic activation in Broca's and Wernicke's aphasia: evidence from eye movements

Lexical processing requires both activating stored representations and selecting among active candidates. The current work uses an eye-tracking paradigm to conduct a detailed temporal investigation of lexical processing. Patients with Broca's and Wernicke's aphasia are studied to shed light on the roles of anterior and posterior brain regions in lexical processing as well as the effects of lexical competition on such processing. Experiment 1 investigates whether objects semantically related to an uttered word are preferentially fixated, for example, given the auditory target "hammer," do participants fixate a picture of a nail? Results show that, like normal controls, both groups of patients are more likely to fixate on an object semantically related to the target than an unrelated object. Experiment 2 explores whether Broca's and Wernicke's aphasics show competition effects when words share onsets with the uttered word, for instance, given the auditory target "hammer," do participants fixate a picture of a hammock? Experiment 3 investigates whether these patients activate words semantically related to onset competitors of the uttered word, for example, given the auditory target "hammock," do participants fixate a nail due to partial activation of the onset competitor hammer? Results of Experiments 2 and 3 show pathological patterns of performance for both Broca's and Wernicke's aphasics under conditions of lexical onset competition. However, the patterns of deficit differed, suggesting different functional and computational roles for anterior and posterior areas in lexical processing. Implications of the findings for the functional architecture of the lexical processing system and its potential neural substrates are considered.