AN INFLUENCE OF SYNTACTIC AND SEMANTIC VARIABLES ON WORD FORM RETRIEVAL

The neural correlates of abstract and concrete words

In this chapter, the literature concerning the dissociation between concrete and abstract words is reviewed, with a specific focus on the role of the temporal lobes. A number of studies have demonstrated the so-called "concreteness effect," that is, the superior processing of concrete versus abstract words. However, some neuropsychological patients have been described with a reversal of concreteness effect, namely, a better performance with abstract than concrete words. Available data suggest that the most frequent causes of this reversed effect are herpes simplex encephalitis and semantic dementia, which typically affect bilaterally anterior temporal regions. Direct electrical stimulation of the left temporal pole further supports this correlation, while the neuroimaging literature is more controversial. In fact, data from neuroimaging studies show either that abstract and concrete noun processing at least partly relies on the activation of a common left-lateralized network, or that abstract word processing is supported by the activation of networks within the left inferior frontal gyrus and the middle temporal gyrus. In between abstract and concrete concepts are idioms, which are represented by concrete actions conveying abstract mental states and events. The involvement of the temporal lobes in processing this particular figure of language is discussed.

An ALE meta-analytical review of the neural correlates of abstract and concrete words

Several clinical studies have reported a double dissociation between abstract and concrete concepts, suggesting that they are processed by at least partly different networks in the brain. However, neuroimaging data seem not in line with neuropsychological reports. Using the ALE method, we run a meta-analysis on 32 brain-activation imaging studies that considered only nouns and verbs. Five clusters were associated with concrete words, four clusters with abstract words. When only nouns were selected three left activation clusters were found to be associated with concrete stimuli and only one with abstract nouns (left IFG). These results confirm that concrete and abstract words processing involves at least partially segregated brain areas, the IFG being relevant for abstract nouns and verbs while more posterior temporoparietal-occipital regions seem to be crucial for processing concrete words, in contrast with the neuropsychological literature that suggests a temporal anterior involvement for concrete words. We investigated the possible reasons that produce different outcomes in neuroimaging and clinical studies.

A case-study of language-specific executive disorder

Executive control is recruited for language processing, particularly in complex linguistic tasks. Although the issue of the existence of an executive control specific to language is still an open issue, there is much evidence that executively-demanding language tasks rely on domain-general rather than language-specific executive resources. Here, we addressed this issue by assessing verbal and non-verbal executive capacities in LG, an aphasic patient after a stroke. First, we showed that LG's performance was spared in all non-verbal tasks regardless of the executive demands. Second, by contrasting conditions of high and low executive demand in verbal tasks, we showed that LG was only impaired in verbal task with high executive demand. The performance dissociation between low and high executive demand conditions in the verbal domain, not observed in the non-verbal domain, shows that verbal executive control partly dissociates from non-verbal executive control. This language-specific executive disorder suggests that some executive processes might be language-specific.

Striatum and language processing: Where do we stand?

More than a century ago, Broca (1861), Wernicke (1874) and Lichteim (1885) laid the foundations for the first anatomo-functional model of language, secondarily enriched by Geschwind (1967), leading to the Broca-Wernicke-Lichteim-Geschwind model. This model included the frontal, parietal, and temporal cortices as well as a subcortical structure, which could be the striatum, whose nature and role have remained unclear. Although the emergence of language deficits in patients with striatal injury has challenged the cortical language models developed over the past 30 years, the integration of the striatum into language processing models remains rare. The main argument for not including the striatum in language processing is that the disorders observed in patients with striatal dysfunction may result from the striatal role in cognitive functions beyond language, and not from the impairment of language itself. Indeed, unraveling the role of the striatum and the frontal cortex, linked by the fronto-striatal pathway, is a challenge. Here, we first reviewed the studies that explored the link between striatal functions and the different levels of language (phonetics, phonology, morphology, syntax, and lexico-semantics). We then looked at the language models, which included the striatum, and found that none of them captured the diversity of experimental data in this area. Finally, we propose an integrative anatomo-functional model of language processing combining traditional language processing levels and some "executive" functions, known to improve the efficiency and fluidity of language: control, working memory, and attention. We argue that within this integrative model, the striatum is a central node of a verbal executive network that regulates, monitors, and controls the allocations of limited cognitive resources (verbal working memory and verbal attention), whatever the language level. This model combines data from neurology, psycholinguistics, and cognitive science.

Saying thirteen instead of forty-two but saying lale instead of tale: is number production special?

Stimulus Type Effect on Phonological and Semantic errors (STEPS) occurs when a person, following brain damage, produces phonemic errors with non-number words (e.g., lale for tale), but produces semantic errors with number words (e.g., thirteen for forty-two). Despite the relative frequency of this phenomenon, it has received little scholarly attention thus far. To explain STEPS, the Building Blocks hypothesis has been proposed (Cohen, Verstichel, & Dehaene, 1997; Dotan & Friedmann, 2015): the phonological output buffer includes single phonemes as the units of speech production for words, whereas entire number words are the building blocks of multi-digit production. Impairment in the phonological output buffer results in the incorrect selection of these units, leading to phonemic errors when producing non-number words, but semantic errors when producing numbers. In the present study we consider two patients, one with a deficit in the phonological output buffer, and one with a deficit in the phonological input buffer but with a preserved phonological output buffer. Number word and non-number word repetition, naming, and reading abilities were assessed. As expected, STEPS was found in the patient with deficits in the phonological output buffer in the three tasks; more notably, evidence of STEPS was also found for the patient with deficits in the phonological input buffer in the repetition task. Since our results cannot be fully explained by the Building Blocks hypothesis in its present form, we discuss the suitability of this hypothesis for the current data, and consider alternative accounts of STEPS.

Investigating the functional neuroanatomy of concrete and abstract word processing through direct electric stimulation (DES) during awake surgery

Neuropsychological, neuroimaging and electrophysiological studies demonstrate that abstract and concrete word processing relies not only on the activity of a common bilateral network but also on dedicated networks. The neuropsychological literature has shown that a selective sparing of abstract relative to concrete words can be documented in lesions of the left anterior temporal regions. We investigated concrete and abstract word processing in 10 patients undergoing direct electrical stimulation (DES) for brain mapping during awake surgery in the left hemisphere. A lexical decision and a concreteness judgment task were added to the neuropsychological assessment during intra-operative monitoring. On the concreteness judgment, DES delivered over the inferior frontal gyrus significantly decreased abstract word accuracy while accuracy for concrete words decreased when the anterior temporal cortex was stimulated. These results are consistent with a lexical-semantic model that distinguishes between concrete and abstract words related to different neural substrates in the left hemisphere.

Patterns of linguistic and numerical performance in aphasia

BACKGROUND

Empirical research on the relationship between linguistic and numerical processing revealed inconsistent results for different levels of cognitive processing (e.g., lexical, semantic) as well as different stimulus materials (e.g., Arabic digits, number words, letters, non-number words). Information of dissociation patterns in aphasic patients was used in order to investigate the dissociability of linguistic and numerical processes. The aim of the present prospective study was a comprehensive, specific, and systematic investigation of relationships between linguistic and numerical processing, considering the impact of asemantic vs. semantic processing and the type of material employed (numbers compared to letters vs. words).

METHODS

A sample of aphasic patients (n = 60) was assessed with a battery of linguistic and numerical tasks directly comparable for their cognitive processing levels (e.g., perceptual, morpho-lexical, semantic).

RESULTS AND CONCLUSIONS

Mean performance differences and frequencies of (complementary) dissociations in individual patients revealed the most prominent numerical advantage for asemantic tasks when comparing the processing of numbers vs. letters, whereas the least numerical advantage was found for semantic tasks when comparing the processing of numbers vs. words. Different patient subgroups showing differential dissociation patterns were further analysed and discussed. A comprehensive model of linguistic and numerical processing should take these findings into account.

Activation of syntax in lexical production in healthy speakers and in aphasia

Theories of spoken word production agree that semantic and phonological representations are activated in spoken word production. There is less agreement concerning the role of syntax. In this study we investigated noun syntax activation in English bare noun naming, using mass and count nouns. Fourteen healthy controls and 13 speakers with aphasia took part. Participants named mass and count nouns, and completed a related noun syntax judgement task. We analysed speakers' noun syntax knowledge when naming accurately, and when making errors in production. Healthy speakers' noun syntax judgement was accurate for words they named correctly, but this did not correlate with naming accuracy. Speakers with aphasia varied in their noun syntax judgement, and this also did not correlate with naming accuracy. Healthy speakers' syntax for semantic errors was less accurate, as was that for speakers with aphasia. For phonological errors half the participants with aphasia could access syntax, half could not, indicating two types of phonological error. Individual differences were found in no responses. Finally, we found no effect of frequency for any of the above. The lack of a relationship between syntax and naming accuracy suggests that syntax is available, but access is not obligatory. This finding supports theories incorporating non-obligatory syntactic processing, which is independent of phonological access. The semantic error data are best explained within such a theory where there is damage to phonological access and hence to independent syntax. For the aphasia group we identify two types of phonological error, one implicating syntax and phonology, and one implicating phonology only, again supporting independent access to these systems. Overall the data support a model within which syntax is independent of phonology, and activation of syntax operates flexibly dependent on task demands and integrity of other processing routines.

Determiner primes as facilitators of lexical retrieval in English

Gender priming studies have demonstrated facilitation of noun production following pre-activation of a target noun's grammatical gender. Findings provide support for models in which syntactic information relating to words is stored within the lexicon and activated during lexical retrieval. Priming effects are observed in the context of determiner plus noun phrase production. Few studies demonstrate gender priming effects in bare noun production (i.e., nouns in isolation). We investigated the effects of English determiner primes on bare mass and count noun production. In two experiments, participants named pictures after exposure to primes involving congruent, incongruent and neutral determiners. Facilitation of noun production by congruent and neutral determiner primes was found in both experiments. The results suggest that noun phrase syntax is activated in lexical retrieval, even when not explicitly required for production. Post hoc analysis of the relative frequency of congruent and incongruent prime-target pairs provides support for a frequency-based interpretation of the data.

An exaggerated effect for proper nouns in a case of superior written over spoken word production

We describe a brain-damaged subject, RR, who manifests superior written over spoken naming of concrete entities from a wide range of conceptual domains. His spoken naming difficulties are due primarily to an impairment of lexical-phonological processing, which implies that his successful written naming does not depend on prior access to the sound structures of words. His performance therefore provides further support for the "orthographic autonomy hypothesis," which maintains that written word production is not obligatorily mediated by phonological knowledge. The case of RR is especially interesting, however, because for him the dissociation between impaired spoken naming and relatively preserved written naming is significantly greater for two categories of unique concrete entities that are lexicalised as proper nouns-specifically, famous faces and famous landmarks-than for five categories of nonunique (i.e., basic level) concrete entities that are lexicalised as common nouns-specifically, animals, fruits/vegetables, tools/utensils, musical instruments, and vehicles. Furthermore, RR's predominant error types in the oral modality are different for the two types of stimuli: omissions for unique entities vs. semantic errors for nonunique entities. We consider two alternative explanations for RR's extreme difficulty in producing the spoken forms of proper nouns: (1) a disconnection between the meanings of proper nouns and the corresponding word nodes in the phonological output lexicon; or (2) damage to the word nodes themselves. We argue that RR's combined behavioural and lesion data do not clearly adjudicate between the two explanations, but that they favour the first explanation over the second.

Is a plum a memory problem? Longitudinal study of the reversal of concreteness effect in a patient with semantic dementia

The concreteness effect, which refers to the typically superior performance for concrete concepts compared to abstract ones, is a robust phenomenon that has been observed in normal and brain-damaged subjects in a number of cognitive domains. Reversal of this effect was also reported in a few neuropsychological studies, mainly in patients with semantic dementia (SD). In this article, we report the first longitudinal single-case study of a patient with SD, SC, who performed better for abstract than concrete concepts in various comprehension and production tasks. For concrete concepts, SC showed no category-specific deficit but was impaired in tasks exploring access to stored structural knowledge and semantic perceptual attributes. With the course of the disease, the semantic system progressively declined and the reversal of the concreteness effect, as well as the dissociation between perceptual and non-perceptual knowledge, vanished. We discuss the results and their implications for theoretical propositions of concreteness effect as well as theoretical models of semantic memory. We suggest that the reversal of concreteness in SC is a direct result of the degradation of visual feature knowledge, sustained by anatomical structures affected early in SD. With the time course of the disease, the atrophy extends to adjacent regions and the dissociation between abstract and concrete concepts was no longer observed.

Information retrieval in Tip of the Tongue states: new data and methodological advances

Research on Tip of the Tongue (ToT) states has been used to determine whether access to syntactic information precedes access to phonological information. This paper argues that previous studies have used insufficient analyses when investigating the nature of seriality of access. In the first part of this paper, these complex issues are discussed and suitable analyses proposed. In the second part, new experimental data are presented. In Experiment 1, English speakers were asked to give information about mass/count status and initial phoneme of nouns, when in a ToT state. In Experiment 2, German speakers were asked to report grammatical gender and initial phoneme of nouns, when in a ToT state. Evidence that syntactic and phonological information are accessed independently was obtained for both languages. Implications for models of language production and further methodological issues in ToT research are discussed.

Deafness for the meanings of number words

We describe the performance of an aphasic individual who showed a selective impairment affecting his comprehension of auditorily presented number words and not other word categories. His difficulty in number word comprehension was restricted to the auditory modality, given that with visual stimuli (written words, Arabic numerals and pictures) his comprehension of number and non-number words was intact. While there have been previous reports of selective difficulty or sparing of number words at the semantic and post-semantic levels, this is the first reported case of a pre-semantic deficit that is specific to the category of number words. This constitutes evidence that lexical semantic distinctions are respected by modality-specific neural mechanisms responsible for providing access to the meanings of words.

The trouble with nouns and verbs in Greek fluent aphasia

In the past verb retrieval problems were associated primarily with agrammatism and noun retrieval difficulties with fluent aphasia. With regards to fluent aphasia, so far in the literature, three distinct patterns of verb/noun dissociations have been described for individuals with fluent anomic aphasia in languages with different underlying forms; better verb retrieval, poorer verb retrieval and equal retrieval difficulties for verbs and nouns. Verbs and nouns in Greek are considered of similar morphological complexity thus it was predicted that anomic aphasic individuals would suffer from a non-dissociated impairment of verbs and nouns. Problems with verbs and/or nouns may arise at any stage in the process of lexical retrieval, i.e. lexical-semantic, lemma, lexeme or articulation. The aim of this research was to investigate verb and noun retrieval using a picture-naming task to explore any possible selective noun and/or verb comprehension or retrieval deficits in Greek individuals with anomic aphasia. The results revealed a significant verb/noun dichotomy with verbs significantly more difficult to retrieve than nouns. These findings lend support for the growing body of evidence showing a specific verb impairment in fluent anomic individuals as well as Broca's patients. Given the prevailing view, that anomic patients experience difficulty retrieving the morpho-phonological form of the target word, the results show that specific information of the grammatical category is also important during word form retrieval. LEARNER OUTCOMES: The reader will become familiar with (i) studies investigating grammatical word class breakdown in individuals with aphasia who speak different languages, (ii) the application of the serial model to word production breakdown in aphasia and (iii) the characteristics of verbs and nouns in Greek. It will be concluded that successful verb retrieval for fluent aphasic individuals who speak Greek is dependant on the retrieval of the morpho-phonological information of the target verb.

Lexical and post-lexical phonological representations in spoken production

Theories of spoken word production generally assume a distinction between at least two types of phonological processes and representations: lexical phonological processes that recover relatively arbitrary aspects of word forms from long-term memory and post-lexical phonological processes that specify the predictable aspects of phonological representations. In this work we examine the spoken production of two brain-damaged individuals. We use their differential patterns of accuracy across the tasks of spoken naming and repetition to establish that they suffer from distinct deficits originating fairly selectively within lexical or post-lexical processes. Independent and detailed analyses of their spoken productions reveal contrasting patterns that provide clear support for a distinction between two types of phonological representations: those that lack syllabic and featural information and are sensitive to lexical factors such as lexical frequency and neighborhood density, and those that include syllabic and featural information and are sensitive to detailed properties of phonological structure such as phoneme frequency and syllabic constituency.

The understanding of quantifiers in semantic dementia: a single-case study

This study investigates the processing of quantifiers in a patient (AM) with semantic dementia. Quantifiers are verbal expressions such as "many" or "a few", which refer semantically to quantity concepts although lexically they are like non-quantity words. Patient AM presented with preserved understanding of quantifier words and impaired understanding of non-quantifier words of the same frequency. In parallel to this, he showed preserved numerical knowledge and impaired comprehension of the meaning of words, objects, and of linguistic concepts. These results suggest that the neural organization of quantifiers is within the numerical domain as they pattern with numerical concepts rather than linguistic concepts. These data reinforce the evidence that numerical knowledge is functionally distinct from non-numerical knowledge in the semantic system and indicate that the semantic referent rather than the stimulus format is more relevant for semantic processing.

Knowing its gender without knowing its name: differential access to lexical information in a jargonaphasic patient

According to recent models of word production, when we name a picture, we first retrieve the meaning of the object, and then we independently retrieve the written or sound form of the word corresponding to the picture. In languages like French, in which words have a gender, theoretical models disagree with respect to the moment at which this information is retrieved. The lemma model (Levelt et al., 1999) posits that we access this information before the sound or written form of the word is retrieved. In contrast, the"Independent network"(IN) model (Caramazza, 1997) model posits that we access gender after retrieval of either the sound or written form of the word. This paper reports a single-case study of an aphasic patient, BA, who showed deficits affecting spoken and written production in the presence of largely preserved comprehension abilities. Experimental testing indicated that she presented with a deficit functionally localized in the access to lexical representations. Results in picture naming and in gender identification also revealed that BA identified the gender above chance level, whether she produced a correct response, a phonemic error, or a neologism. In contrast, when she was unable to produce a spoken or written response, she could not identify the gender. This pattern of performance is consistent with the lemma model in which access to lexical syntax is required before access to phonological form can take place.