Density pervades: an analysis of phonological neighbourhood density effects in aphasic speakers with different types of naming impairment

Visual Attention to Semantic and Orthographic Associations in Fluent Aphasia: Evidence from Eye-Tracking

We examined the allocation of visual attention in an association task by both neurotypical participants (n = 11) and adults with fluent aphasia (n = 12). Participants were presented with a picture (e.g., a basket) followed by a semantically related association (i.e., "strawberry") and an orthographically related association (i.e., "b," the first letter of "basket"). An eye tracker recorded their eye movements for three areas of interest (AOI): the picture, the semantic associate, and the orthographic associate, over 1396 observations. Results showed that both neurotypical participants and participants with aphasia looked longer at the semantic associate than at the picture, and this difference was more pronounced for neurotypicals than for people with aphasia (PWA). Neurotypicals also looked longer than the PWA group at the orthographic associate than at the prior picture. Regarding eye fixation counts, both participant groups looked more frequently at the semantic associate than at either the picture or the orthographic associate. Notably, this pattern was more pronounced among neurotypical participants than PWA. Our findings emphasize the importance of semantic associations in fluent aphasia and suggest a potential rehabilitative approach in speech and language therapy.

Phonological neighbourhood effects in Italian speech production: Evidence from healthy and neurologically impaired populations

In two speech production studies conducted in Italian, we investigated the impact of phonological neighbourhood properties such as the neighbourhood density and the mean frequency of the neighbours on speech processing. Two populations of healthy (Study 1) and neurologically impaired (Study 2) individuals were tested. We employed multi-regression methods to analyse naming latencies in Study 1 and accuracy rates in Study 2 while controlling for various psycholinguistic predictors. In Study 1, pictures with words from high-density neighbourhoods were named faster than those from low-density neighbourhoods. Additionally, words with high-frequency neighbours were named faster in Study 1 and yielded higher accuracy rates in Study 2. The results suggest facilitatory effects of both the phonological neighbourhood density and frequency neighbourhood variables. Furthermore, we observed interactions between these two phonological neighbourhood variables and name agreement and repetition. Specifically, the facilitation effect was more pronounced for pictures with lower name agreement and during the initial presentation of the pictures. These findings are discussed in the context of previous literature and within the framework of interactive models of speech production.

Multilevel factors predict treatment response following semantic feature-based intervention in bilingual aphasia

Semantic feature-based treatments (SFTs) are effective rehabilitation strategies for word retrieval deficits in bilinguals with aphasia (BWA). However, few studies have prospectively evaluated the effects of key parameters of these interventions on treatment outcomes. This study examined the influence of intervention-level (i.e., treatment language and treatment sessions), individual-level (baseline naming severity and age), and stimulus-level (i.e., lexical frequency, phonological length, and phonological neighborhood density) factors on naming improvement in a treated and untreated language for 34 Spanish-English BWA who completed 40 hours of SFT. Results revealed significant improvement over time in both languages. In the treated language, individuals who received therapy in their L1 improved more. Additionally, higher pre-treatment naming scores predicted greater response to treatment. Finally, a frequency effect on baseline naming accuracy and phonological effects on accuracy over time were associated with differential treatment gains. These findings indicate that multilevel factors are influential predictors of bilingual treatment outcomes.

Verbal fluency tests assess global cognitive status but have limited diagnostic differentiation: evidence from a large-scale examination of six neurodegenerative diseases

Verbal fluency is widely used as a clinical test, but its utility in differentiating between neurodegenerative dementias and progressive aphasias, and from healthy controls, remains unclear. We assessed whether various measures of fluency performance could differentiate between Alzheimer's disease, behavioural variant of frontotemporal dementia, non-fluent and semantic variants of primary progressive aphasia, progressive supranuclear palsy, corticobasal syndrome and healthy controls. Category and letter fluency tasks were administered to 33 controls and 139 patients at their baseline clinical visit. We assessed group differences for total number of words produced, psycholinguistic word properties and associations between production order and exemplar psycholinguistic properties. Receiver operating characteristic curves determined which measure could best discriminate patient groups and controls. The total word count distinguished controls from all patient groups, but neither this measure nor the word properties differentiated the patient groups. Receiver operating characteristic curves revealed that, when comparing controls to patients, the strongest discriminators were total word count followed by word frequency. Word frequency was the strongest discriminator for semantic variant of primary progressive aphasia versus other groups. Fluency word counts were associated with global severity as measured by Addenbrooke's Cognitive Examination Revised. Verbal fluency is an efficient test for assessing global brain-cognitive health but has limited utility in differentiating between cognitively and anatomically disparate patient groups. This outcome is consistent with the fact that verbal fluency requires many different aspects of higher cognition and language.

Stimulus- and Person-Level Variables Influence Word Production and Response to Anomia Treatment for Individuals With Chronic Poststroke Aphasia

PURPOSE

The impact of stimulus-level psycholinguistic variables and person-level semantic and phonological processing skills on treatment outcomes in individuals with aphasia requires further examination to inform clinical decision making in treatment prescription and stimuli selection. This study investigated the influence of stimulus-level psycholinguistic properties and person-level semantic and phonological processing skills on word production accuracy and treatment response.

METHOD

This retrospective analysis included 35 individuals with chronic, poststroke aphasia, 30 of whom completed typicality-based semantic feature treatment. Mixed-effects logistic regression models were used to predict binary naming accuracy (a) at baseline and (b) over the course of treatment using stimulus-level psycholinguistic word properties and person-level semantic and phonological processing skills as predictors.

RESULTS

In baseline naming, words with less complex lexical-semantic and phonological properties showed greater predicted accuracy. There was also an interaction at baseline between stimulus-level lexical-semantic properties and person-level semantic processing skills in predicting baseline naming accuracy. With treatment, words that were more complex from a lexical-semantic standpoint (vs. less complex) and less complex from a phonological standpoint (vs. more complex) improved more. Individuals with greater baseline semantic and phonological processing skills showed a greater treatment response.

CONCLUSIONS

This study suggests that future clinical research and clinical work should consider semantic and phonological properties of words in selecting stimuli for semantically based treatment. Furthermore, future clinical research should continue to evaluate baseline individual semantic and phonological profiles as predictors of response to semantically based treatment.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21256341.

Validation of the Iowa Test of Consonant Perception

Speech perception (especially in background noise) is a critical problem for hearing-impaired listeners and an important issue for cognitive hearing science. Despite a plethora of standardized measures, few single-word closed-set tests uniformly sample the most frequently used phonemes and use response choices that equally sample phonetic features like place and voicing. The Iowa Test of Consonant Perception (ITCP) attempts to solve this. It is a proportionally balanced phonemic word recognition task designed to assess perception of the initial consonant of monosyllabic consonant-vowel-consonant (CVC) words. The ITCP consists of 120 sampled CVC words. Words were recorded from four different talkers (two female) and uniformly sampled from all four quadrants of the vowel space to control for coarticulation. Response choices on each trial are balanced to equate difficulty and sample a single phonetic feature. This study evaluated the psychometric properties of ITCP by examining reliability (test-retest) and validity in a sample of online normal-hearing participants. Ninety-eight participants completed two sessions of the ITCP along with standardized tests of words and sentence in noise (CNC words and AzBio sentences). The ITCP showed good test-retest reliability and convergent validity with two popular tests presented in noise. All the materials to use the ITCP or to construct your own version of the ITCP are freely available [Geller, McMurray, Holmes, and Choi (2020). https://osf.io/hycdu/].

Methodological Considerations for Incorporating Clinical Data Into a Network Model of Retrieval Failures

Difficulty retrieving information (e.g., words) from memory is prevalent in neurogenic communication disorders (e.g., aphasia and dementia). Theoretical modeling of retrieval failures often relies on clinical data, despite methodological limitations (e.g., locus of retrieval failure, heterogeneity of individuals, and progression of disorder/disease). Techniques from network science are naturally capable of handling these limitations. This paper reviews recent work using a multiplex lexical network to account for word retrieval failures and highlights how network science can address the limitations of clinical data. Critically, any model we employ could impact clinical practice and patient lives, harkening the need for theoretically well-informed network models.

When phonological neighborhood density both facilitates and impedes: Age of acquisition and name agreement interact with phonological neighborhood during word production

The number of similar-sounding words that a target word has, or its Phonological Neighborhood Density (PND), has been shown to influence word production. However, reported results are sometimes inconsistent, with studies showing facilitation, inhibition, and null effects of phonological neighbors. These mixed results may be due to the influence of other factors beyond PND. We investigated the potential interactions between a broad measure of PND (bPND), and age of acquisition (AoA), frequency, and name agreement in order to see if the effect of bPND varies as a function of these three variables. We examined the effect of bPND on the latency of picture naming and observed significant interactions between bPND and AoA such that bPND facilitated lexical retrieval for words that were acquired early, but inhibited retrieval for words acquired later in life. We hypothesize that lexical retrieval difficulty ultimately depends on the activation level of the target word's phonological representations relative to the activation levels of its neighbors' phonological representations. When phonological features of the target word are weakly activated (i.e., late AoA), and bPND is high, the neighbors' activation may overshadow the target's, impeding target retrieval. However, when the target's phonological representation is strongly activated, the activation of the neighbors might not exceed that of the target, thereby supporting phonological retrieval. We also observed interactions between bPND and name agreement such that increasing bPND led to faster reaction times (RTs), particularly when name agreement was lower, suggesting that bPND may also facilitate word retrieval when lexical competition is high.

Mapping psycholinguistic features to the neuropsychological and lesion profiles in aphasia

Naming and word retrieval deficits are two of the most persistent symptoms in chronic post-stroke aphasia. Naming success or failure on specific words can sometimes be predicted by the psycholinguistic properties of the word. Despite a wealth of literature investigating the influence of psycholinguistic properties in neuro-typical and clinical language processing, the underlying structure of these properties and their relation to the fundamental language components and neural correlates are unexplored. In this study, a multivariate data-decomposition approach was used to identify the underlying structure within a collection of psycholinguistic properties (word imageability, frequency, age-of-acquisition, familiarity, length, semantic diversity and phonological neighbourhood density) and their influence on naming accuracy was explored in a cohort of 42 participants with a diverse range of chronic post-stroke aphasia classifications and severities. The results extracted three principal psycholinguistic factors, which were best described as 'lexical usage', 'semantic clarity' and 'phonological complexity'. Furthermore, a novel approach was used to systematically relate the influence of these psycholinguistic properties to participants' neuropsychological and lesion profiles. The findings did not show a one-to-one mapping between psycholinguistic features and core language components. 'Lexical usage' was the only factor that showed a significant difference between fluent versus non-fluent aphasia groups in terms of the influence of this lexical factor on successful naming, and it was the only factor that was related to the pattern of patients' brain lesions. Voxel-wise whole brain lesion-symptom mapping identified left frontal regions, aligning with previous evidence that these regions are related to language production functions, including word retrieval and repetition. The evidence from the current study suggests that the functional locus of psycholinguistic properties is distributed across multiple language components rather than being localised to a single language element.

Semantic and lexical features of words dissimilarly affected by non-fluent, logopenic, and semantic primary progressive aphasia

OBJECTIVE

To determine the effect of three psycholinguistic variables-lexical frequency, age of acquisition (AoA), and neighborhood density (ND)-on lexical-semantic processing in individuals with non-fluent (nfvPPA), logopenic (lvPPA), and semantic primary progressive aphasia (svPPA). Identifying the scope and independence of these features can provide valuable information about the organization of words in our mind and brain.

METHOD

We administered a lexical decision task-with words carefully selected to permit distinguishing lexical frequency, AoA, and orthographic ND effects-to 41 individuals with PPA (13 nfvPPA, 14 lvPPA, 14 svPPA) and 25 controls.

RESULTS

Of the psycholinguistic variables studied, lexical frequency had the largest influence on lexical-semantic processing, but AoA and ND also played an independent role. The results reflect a brain-language relationship with different proportional effects of frequency, AoA, and ND in the PPA variants, in a pattern that is consistent with the organization of the mental lexicon. Individuals with nfvPPA and lvPPA experienced an ND effect consistent with the role of inferior frontal and temporoparietal regions in lexical analysis and word form processing. By contrast, individuals with svPPA experienced an AoA effect consistent with the role of the anterior temporal lobe in semantic processing.

CONCLUSIONS

The findings are in line with a hierarchical mental lexicon structure with a conceptual (semantic) and a lexeme (word-form) level, such that a selective deficit at one of these levels of the mental lexicon manifests differently in lexical-semantic processing performance, consistent with the affected language-specific brain region in each PPA variant.

Orthographic Visualisation Induced Brain Activations in a Chronic Poststroke Global Aphasia with Dissociation between Oral and Written Expression

We propose a method of orthographic visualisation strategy in a poststroke severe aphasia person with dissociation between oral and written expression. fMRI results suggest that such strategy may induce the engagement of alternative nonlanguage networks and visual representations may help improving oral output. This choice of rehabilitation method can be based on the remaining capacities and, therefore, on written language. Most notably, no study so far addressed how orthographic visualisation strategy during speech rehabilitation might influence clinical outcomes in nonfluent aphasia and apraxia patients.

Phonological neighborhood effect in spontaneous speech in adults who stutter

PURPOSE

The study examined the relationship between word-form similarity network (phonological neighborhood) and stuttering occurrence in spontaneous speech in adults. The study asked whether neighborhood characteristics, including the number of neighbors (neighborhood density) and the average word frequency among neighbors (neighborhood frequency), differentiate stuttered from fluent words within spontaneous speech samples, and more specifically, whether neighborhood characteristics facilitate speech fluency in adults who stutter.

METHOD

Spontaneous speech samples were collected from 14 adults who stutter, including 7 with mild stuttering and 7 with severe stuttering. Each stuttered word was matched with a fluently produced word within the sample, controlling for multiple lexical factors. Neighborhood density and neighborhood frequency were compared between the stuttered and matched fluent words.

RESULTS

Adults stuttered on words with lower neighborhood density, compared to fluently produced words, with similar patterns in the two severity subgroups. There appeared to be a marginal difference between single-syllable whole-word repetition and the other stuttering typologies.

CONCLUSION

Neighborhood density facilitates fluent word production in spontaneous speech in adults who stutter, regardless of stuttering severity. This finding adds to the evidence supporting that phonological encoding plays a role in stuttering in naturalistic, spontaneous speech in adults.

Effects of Prefrontal Transcranial Direct Current Stimulation on Lexical Access in Chronic Poststroke Aphasia

Background. A successful interplay between prefrontal and domain-specific language areas is critical for language processing. Previous studies involving people with aphasia have shown that executive control processes might act on lexical-semantic representations during retrieval. Modulating the prefrontal control network by means of noninvasive brain stimulation might, therefore, improve lexical access in people with aphasia. Objective. The present study investigates the effects of prefrontal transcranial direct current stimulation (tDCS) on lexical access in chronic poststroke aphasia. Methods. We report data of 14 participants with chronic poststroke aphasia. We used a sham-tDCS (S-tDCS) controlled and double-blind within-subjects design. Performances in picture naming, verbal fluency, and word repetition were assessed immediately after stimulation. Results. As compared with S-tDCS, anodal tDCS (A-tDCS) improved verbal fluency as well as the speed of naming high frequency words, but not word repetition. Conclusion. The results of our study suggest that the brain network dedicated to lexical retrieval processing can be facilitated by A-tDCS over the left dorsolateral prefrontal cortex. This finding supports the notion that strengthening executive control functions after stroke could complement speech and language-focused therapy.

What Does a Cue Do? Comparing Phonological and Semantic Cues for Picture Naming in Aphasia

PURPOSE

Impaired naming is one of the most common symptoms in aphasia, often treated with cued picture naming paradigms. It has been argued that semantic cues facilitate the reliable categorization of the picture, and phonological cues facilitate the retrieval of target phonology. To test these hypotheses, we compared the effectiveness of phonological and semantic cues in picture naming for a group of individuals with aphasia. To establish the locus of effective cueing, we also tested whether cue type interacted with lexical and image properties of the targets.

METHOD

Individuals with aphasia (n = 10) were tested with a within-subject design. They named a large set of items (n = 175) 4 times. Each presentation of the items was accompanied by a different cueing condition (phonological, semantic, nonassociated word and tone). Item level variables for the targets (i.e., phoneme length, frequency, imageability, name agreement, and visual complexity) were used to test the interaction of cue type and item variables. Naming accuracy data were analyzed using generalized linear mixed effects models.

RESULTS

Phonological cues were more effective than semantic cues, improving accuracy across individuals. However, phonological cues did not interact with phonological or lexical aspects of the picture names (e.g., phoneme length, frequency). Instead, they interacted with properties of the picture itself (i.e., visual complexity), such that phonological cues improved naming accuracy for items with low visual complexity.

CONCLUSIONS

The findings challenge the theoretical assumptions that phonological cues map to phonological processes. Instead, phonological information benefits the earliest stages of picture recognition, aiding the initial categorization of the target. The data help to explain why patterns of cueing are not consistent in aphasia; that is, it is not the case that phonological impairments always benefit from phonological cues and semantic impairments form semantic cues. A substantial amount of the literature in naming therapy focuses on picture naming paradigms. Therefore, the results are also critically important for rehabilitation, allowing for therapy development to be more rooted in the true mechanisms through which cues are processed.

Objective support for subjective reports of successful inner speech in two people with aphasia

People with aphasia frequently report being able to say a word correctly in their heads, even if they are unable to say that word aloud. It is difficult to know what is meant by these reports of "successful inner speech". We probe the experience of successful inner speech in two people with aphasia. We show that these reports are associated with correct overt speech and phonologically related nonword errors, that they relate to word characteristics associated with ease of lexical access but not ease of production, and that they predict whether or not individual words are relearned during anomia treatment. These findings suggest that reports of successful inner speech are meaningful and may be useful to study self-monitoring in aphasia, to better understand anomia, and to predict treatment outcomes. Ultimately, the study of inner speech in people with aphasia could provide critical insights that inform our understanding of normal language.

Norwegian words: A lexical database for clinicians and researchers

All words have properties linked to form, meaning and usage patterns which influence how easily they are accessed from the mental lexicon in language production, perception and comprehension. Examples of such properties are imageability, phonological and morphological complexity, word class, argument structure, frequency of use and age of acquisition. Due to linguistic and cultural variation the properties and the values associated with them differ across languages. Hence, for research as well as clinical purposes, language specific information on lexical properties is needed. To meet this need, an electronically searchable lexical database with more than 1600 Norwegian words coded for more than 12 different properties has been established. This article presents the content and structure of the database as well as the search options available in the interface. Finally, it briefly describes some of the ways in which the database can be used in research, clinical practice and teaching.

Friends and foes in the lexicon: homophone naming in aphasia

The study of homophones--words with different meanings that sound the same--has great potential to inform models of language production. Of particular relevance is a phenomenon termed frequency inheritance, where a low-frequency word (e.g., deer) is produced more fluently than would be expected based on its frequency characteristics, presumably because of shared phonology with a high-frequency homophone counterpart (e.g., dear). However, prior studies have been inconsistent in showing frequency inheritance. To explain this inconsistency, we propose a dual nature account of homophony: a high-frequency counterpart exerts 2 counterposing effects on a low-frequency homophone target during the 2 main stages of naming: (a) a detrimental impact during semantically driven lexical retrieval; (b) a beneficial impact during phonological retrieval. In a study of naming in participants with chronic aphasia followed by computational investigations, we find strong evidence for the dual nature account of homophony.

The Aging Neighborhood: Phonological Density in Naming

Aging affects the ability to retrieve words for production, despite maintainence of lexical knowledge. In this study, we investigate the influence of lexical variables on picture naming accuracy and latency in adults ranging in age from 22 to 86 years. In particular, we explored the influence of phonological neighborhood density, which has been shown to exert competitive effects on word recognition, but to facilitate word production, a finding with implications for models of the lexicon. Naming responses were slower and less accurate for older participants, as expected. Target frequency also played a strong role, with facilitative frequency effects becoming stronger with age. Neighborhood density interacted with age, such that naming was slower for high-density than low-density items, but only for older subjects. Explaining this finding within an interactive activation model suggests that, as we age, the ability of activated neighbors to facilitate target production diminishes, while their activation puts them in competition with the target.

Theoretical analysis of word production deficits in adult aphasia

The cognitive analysis of adult language disorders continues to draw heavily on linguistic theory, but increasingly it reflects the influence of connectionist, spreading activation models of cognition. In the area of spoken word production, 'localist' connectionist models represent a natural evolution from the psycholingistic theories of earlier decades. By contrast, the parallel distributed processing framework forces more radical rethinking of aphasic impairments. This paper exemplifies these multiple influences in contemporary cognitive aphasiology. Topics include (i) what aphasia reveals about semantic-phonological interaction in lexical access; (ii) controversies surrounding the interpretation of semantic errors and (iii) a computational account of the relationship between naming and word repetition in aphasia. Several of these topics have been addressed using case series methods, including computational simulation of the individual, quantitative error patterns of diverse groups of patients and analysis of brain lesions that correlate with error rates and patterns. Efforts to map the lesion correlates of nonword errors in naming and repetition highlight the involvement of sensorimotor areas in the brain and suggest the need to better integrate models of word production with models of speech and action.

Competition and cooperation among similar representations: toward a unified account of facilitative and inhibitory effects of lexical neighbors

One of the core principles of how the mind works is the graded, parallel activation of multiple related or similar representations. Parallel activation of multiple representations has been particularly important in the development of theories and models of language processing, where coactivated representations (neighbors) have been shown to exhibit both facilitative and inhibitory effects on word recognition and production. Researchers generally ascribe these effects to interactive activation and competition, but there is no unified explanation for why the effects are facilitative in some cases and inhibitory in others. We present a series of simulations of a simple domain-general interactive activation and competition model that is broadly consistent with more specialized domain-specific models of lexical processing. The results showed that interactive activation and competition can indeed account for the complex pattern of reversals. Critically, the simulations revealed a core computational principle that determines whether neighbor effects are facilitative or inhibitory: strongly active neighbors exert a net inhibitory effect, and weakly active neighbors exert a net facilitative effect.