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BACKGROUND: Although considerable research has been conducted on post-COVID-19 syndrome (PCS), cognitive symptoms, particularly those related to language, are still not well understood. AIMS: To provide a detailed quantitative and qualitative analysis of language performance in PCS patients using a comprehensive set of semantic and verbal production tasks. METHODS & PROCEDURES: The study involved 195 PCS patients aged 26-64 years and 50 healthy controls aged 25-61 years. Participants were assessed using two semantic tasks, three naming tasks and four types of verbal fluency tasks, designed to evaluate different aspects of language processing. OUTCOMES & RESULTS: PCS patients demonstrated significantly poorer performance compared with controls across all verbal fluency tasks. This was evident in both the total number of words generated and their types, with patients tending to choose more easily accessible words. In naming tasks, the pattern of errors was similar in both groups, although patients showed a higher number of non-responses and made more errors, reflecting difficulties in word retrieval. The analysis highlighted the impact of factors such as stimulus availability, educational level and cognitive reserve on performance. Notably, younger patients performed worse than older, a paradoxical trend also observed in previous research. CONCLUSIONS & IMPLICATIONS: These findings reveal significant word retrieval difficulties in PCS patients, suggesting that cognitive impairment related to language may be more pronounced than previously understood. The results underscore the need for a thorough evaluation of language functions in PCS patients and the development of more targeted and individualized language rehabilitation strategies to address these specific challenges. WHAT THIS PAPER ADDS: What is already known on the subject Studies on the cognitive characteristics of CPS have focused mainly on broad-spectrum neuropsychological assessments covering all cognitive functions. However, there are very few studies analysing oral production with specific lexical and semantic system tasks. Furthermore, no work has specifically included tasks assessing semantic processing or conducted qualitative analyses of the psycholinguistic variables affecting performance. Such analyses could undoubtedly help clarify the nature of the language impairments in patients with PCS. What this paper adds to the existing knowledge This study explores in depth the evaluation and analysis of the oral production of patients with PCS using several lexical and semantic tasks. In addition, psycholinguistic variables are analysed that could undoubtedly help clarify the nature of the language impairments in patients with PCS. What are the potential or actual clinical implications of this work? The study allows the identification of specific lexical-semantic deficits in the spoken language in patients with this PCS. A more detailed assessment of the oral language of these patients, keeping in mind the psycholinguistic variables that may affect the performance, will facilitate the design of more efficient and individualized rehabilitation programmes.
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Name agreement (NA) refers to the degree to which speakers agree on a picture's name. A robust finding is that speakers are faster to name pictures with high agreement (HA) than those with low agreement (LA). This NA effect is thought to occur because LA pictures strongly activate several names, so speakers need time to select one. HA pictures, in contrast, strongly activate a single name, so there is no need to select one name out of several alternatives. Recent models of lexical access suggest that the structure of the mental lexicon changes with experience. Thus, speakers should consider a range of names when naming LA pictures, but the extent to which they consider each of these names should change with experience. We tested these hypotheses in two picture-naming experiments. In Experiment 1, participants were faster to name LA than HA pictures when they named each picture once. Importantly, they were faster to produce modal names (provided by most participants) than alternative names for LA pictures, consistent with the view that speakers activate multiple names for LA pictures. In Experiment 2, participants were familiarised with the modal name before the experiment and named each picture three times. Although there was still an NA effect when participants named the pictures the first time, it was reduced in comparison to Experiment 1 and was further reduced with each picture repetition. Thus, familiarisation and repetition reduced the NA effect but did not eliminate it, suggesting speakers activate a range of plausible names.
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Theories of bilingual language production predict that bilinguals with Alzheimer's disease (AD) should exhibit one of two decline patterns. Either parallel decline of both languages (if decline reflects damage to semantic representations that are accessed by both languages), or asymmetrical decline, with greater decline of the nondominant language (if decline reflects reduced ability to resolve competition from the dominant language with disease progression). Only two previous studies examined decline longitudinally with one showing parallel, and the other asymmetrical, decline. We examined decline over 2-7 years (3.9 on average) in Spanish-English bilinguals (N = 23). Logistic regression revealed a parallel decline pattern at one year from baseline, but an asymmetrical decline pattern over the longer decline period, with greater decline of the nondominant language (when calculating predicted probabilities of a correct response). The asymmetrical decline pattern was significantly greater for the nondominant language only when including item-difficulty in the model. Exploratory analyses across dominance groups looking at proportional decline relative to initial naming accuracy further suggested that decline of the nondominant language may be more precipitous if that language was acquired later in life, but the critical interaction needed to support this possibility was not statistically significant in a logistic regression analysis. These results suggest that accessibility of the nondominant language may initially be more resilient in early versus more advanced AD, and that AD affects shared semantic representations before executive control declines to a point where the ability to name pictures in single-language testing block is disrupted. Additional work is needed to determine if asymmetrical decline patterns are magnified by late age of acquisition of the nondominant language, and if more subtle impairments to executive control underlie impairments to language switching that occur in the earliest stages of AD (even preclinically).
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Doença de Alzheimer , Multilinguismo , Humanos , Doença de Alzheimer/fisiopatologia , Masculino , Feminino , Idoso , Estudos Longitudinais , Idoso de 80 Anos ou mais , Progressão da Doença , Testes Neuropsicológicos , Testes de Linguagem , Transtornos da Linguagem/etiologia , Transtornos da Linguagem/fisiopatologia , Transtornos da Linguagem/diagnósticoRESUMO
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.
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Object recognition and visual categorization are typically swift and seemingly effortless tasks that involve numerous underlying processes. In our investigation, we utilized a picture naming task to explore the processing of rarely encountered objects (visual hapaxes) in comparison to common objects. Our aim was to determine the stage at which these rare objects are classified as unnamable. Contrary to our expectations and in contrast to some prior research on event-related potentials (ERPs) with novel and atypical objects, no differences between conditions were observed in the late time windows corresponding to the P300 or N400 components. However, distinctive patterns between hapaxes and common objects surfaced in three early time windows, corresponding to the posterior N1 and P2 waves, as well as a widespread N2 wave. According to the ERP data, the differentiation between hapaxes and common objects occurs within the first 380 ms of the processing line, involving only limited and indirect top-down influence.
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Eletroencefalografia , Potenciais Evocados , Reconhecimento Visual de Modelos , Estimulação Luminosa , Tempo de Reação , Humanos , Masculino , Feminino , Estimulação Luminosa/métodos , Reconhecimento Visual de Modelos/fisiologia , Adulto , Adulto Jovem , Potenciais Evocados/fisiologia , Tempo de Reação/fisiologia , Mapeamento Encefálico , Potenciais Evocados Visuais/fisiologia , Análise de Variância , AdolescenteRESUMO
Behavioral and brain-related changes in word production have been claimed to predominantly occur after 70 years of age. Most studies investigating age-related changes in adulthood only compared young to older adults, failing to determine whether neural processes underlying word production change at an earlier age than observed in behavior. This study aims to fill this gap by investigating whether changes in neurophysiological processes underlying word production are aligned with behavioral changes. Behavior and the electrophysiological event-related potential patterns of word production were assessed during a picture naming task in 95 participants across five adult lifespan age groups (ranging from 16 to 80 years old). While behavioral performance decreased starting from 70 years of age, significant neurophysiological changes were present at the age of 40 years old, in a time window (between 150 and 220 ms) likely associated with lexical-semantic processes underlying referential word production. These results show that neurophysiological modifications precede the behavioral changes in language production; they can be interpreted in line with the suggestion that the lexical-semantic reorganization in mid-adulthood influences the maintenance of language skills longer than for other cognitive functions.
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Envelhecimento , Eletroencefalografia , Potenciais Evocados , Humanos , Adulto , Idoso , Masculino , Pessoa de Meia-Idade , Feminino , Adulto Jovem , Adolescente , Idoso de 80 Anos ou mais , Envelhecimento/fisiologia , Potenciais Evocados/fisiologia , Encéfalo/fisiologia , Fala/fisiologia , SemânticaRESUMO
Objective: Research demonstrates that college educated, English language dominant bilinguals underperform relative to English speaking monolinguals on tests of verbal ability. We investigated whether accepting responses in their two languages would reveal improved performance in bilinguals, and whether such improvement would be of sufficient magnitude to demonstrate the same performance level as monolinguals. Method: Participants were college students attending the same university. Spanish-English bilinguals were compared to English speaking monolinguals on the Bilingual Verbal Ability Tests (BVAT), which include Picture Vocabulary, Oral Vocabulary, and Verbal Analogies. Results: When given the opportunity to respond in Spanish to items failed in English, bilinguals obtained significantly higher scores on all three subtests, and their performance matched that of monolinguals on Oral Vocabulary and Verbal Analogies. Conclusion: An "either-language" scoring approach may enable optimal measurement of verbal abilities in bilinguals. We provide normative data for use in applying the either-language scoring approach on subtests of the BVAT. We discuss the findings in the context of clinical assessment.
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A picture naming test (PNT) has long been regarded as an integral part of neuropsychological assessment. In current research and clinical practice, it serves a variety of purposes. PNTs are used to assess the severity of speech impairment in aphasia, monitor possible cognitive decline in aging patients with or without age-related neurodegenerative disorders, track language development in children and map eloquent brain areas to be spared during surgery. In research settings, picture naming tests provide an insight into the process of lexical retrieval in monolingual and bilingual speakers. However, while numerous advances have occurred in linguistics and neuroscience since the classic, most widespread PNTs were developed, few of them have found their way into test design. Consequently, despite the popularity of PNTs in clinical and research practice, their relevance and objectivity remain questionable. The present study provides an overview of literature where relevant criticisms and concerns have been expressed over the recent decades. It aims to determine whether there is a significant gap between conventional test design and the current understanding of the mechanisms underlying lexical retrieval by focusing on the parameters that have been experimentally proven to influence picture naming. We discuss here the implications of these findings for improving and facilitating test design within the picture naming paradigm. Subsequently, we highlight the importance of designing specialized tests with a particular target group in mind, so that test variables could be selected for cerebellar tumor survivors.
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The present study presents picture-naming norms for a large set of 800 high-quality photographs of 200 natural objects and artefacts spanning a range of categories, with four unique images per object. Participants were asked to provide a single, most appropriate name for each image seen. We report recognition latencies for each image, and several normed variables for the provided names: agreement, H-statistic (i.e. level of naming uncertainty), Zipf word frequency and word length. Rather than simply focusing on a single name per image (i.e. the modal or most common name), analysis of recognition latencies showed that it is important to consider the diversity of labels that participants may ascribe to each pictured object. The norms therefore provide a list of candidate labels per image with weighted measures of word length and frequency per image that incorporate all provided names, as well as modal measures based on the most common name only.
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Reconhecimento Visual de Modelos , Humanos , Feminino , Masculino , Adulto , Adulto Jovem , Reconhecimento Visual de Modelos/fisiologia , Reconhecimento Psicológico/fisiologia , Fotografação/métodos , Tempo de Reação/fisiologia , Nomes , Idioma , Adolescente , Estimulação LuminosaRESUMO
BACKGROUND: Studies on late talkers (LTs) highlighted their heterogeneity and the relevance of describing different communicative profiles. AIMS: To examine lexical skills and gesture use in expressive (E-LTs) vs. receptive-expressive (R/E-LTs) LTs through a structured task. METHODS AND PROCEDURES: Forty-six 30-month-old screened LTs were distinguished into E-LTs (n= 35) and R/E-LTs (n= 11) according to their receptive skills. Lexical skills and gesture use were assessed with a Picture Naming Game by coding answer accuracy (correct, incorrect, no response), modality of expression (spoken, spoken-gestural, gestural), type of gestures (deictic, representational), and spoken-gestural answers' semantic relationship (complementary, equivalent, supplementary). OUTCOMES AND RESULTS: R/E-LTs showed lower scores than E-LTs for noun and predicate comprehension with fewer correct answers, and production with fewer correct and incorrect answers, and more no responses. R/E-LTs also exhibited lower scores in spoken answers, representational gestures, and equivalent spoken-gestural answers for noun production and in all spoken and gestural answers for predicate production. CONCLUSIONS AND IMPLICATIONS: Findings highlighted more impaired receptive and expressive lexical skills and lower gesture use in R/E-LTs compared to E-LTs, underlying the relevance of assessing both lexical and gestural skills through a structured task, besides parental questionnaires and developmental scales, to describe LTs' communicative profiles.
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Gestos , Transtornos do Desenvolvimento da Linguagem , Humanos , Compreensão/fisiologia , Pais , Testes de Linguagem , VocabulárioRESUMO
Speakers sometimes make word production errors, such as mistakenly saying pelican instead of flamingo. This study explored which properties of an error influence the likelihood of its selection over the target word. Analysing real-word errors in speeded picture naming, we investigated whether, relative to the target, naming errors were more typical representatives of the semantic category, were associated with more semantic features, and/or were semantically more closely related to the target than its near semantic neighbours were on average. Results indicated that naming errors tended to be more typical category representatives and possess more semantic features than the targets. Moreover, while not being the closest semantic neighbours, errors were largely near semantic neighbours of the targets. These findings suggest that typicality, number of semantic features, and semantic similarity govern activation levels in the production system, and we discuss possible mechanisms underlying these effects in the context of word production theories.
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Semântica , Humanos , Feminino , Masculino , Adulto , Tempo de Reação/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Adulto Jovem , Fala/fisiologiaRESUMO
Semantic interference (SI) and phonological facilitation (PF) effects occur when multiple representations are co-activated simultaneously in complex naming paradigms, manipulating the context in which word production is set. Although the behavioral consequences of these psycholinguistic effects are well-known, the involved brain structures are still controversial. This paper aims to provide a systematic review and a coordinate-based meta-analysis of the available functional neuroimaging studies investigating SI and PF in picture naming paradigms. The included studies were fMRI experiments on healthy subjects, employing paradigms in which co-activations of representations were obtained by manipulating the naming context using semantically or phonologically related items. We examined the principal methodological aspects of the included studies, emphasizing the existing commonalities and discrepancies across single investigations. We then performed an exploratory coordinate-based meta-analysis of the reported activation peaks of neural response related to SI and PF. Our results consolidated previous findings regarding the involvement of the left inferior frontal gyrus and the left middle temporal gyrus in SI and brought out the role of bilateral inferior parietal regions in PF.
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Does neural activity reveal how balanced bilinguals choose languages? Despite using diverse neuroimaging techniques, prior studies haven't provided a definitive solution to this problem. Nonetheless, studies involving direct brain stimulation in bilinguals have identified distinct brain regions associated with language production in different languages. In this magnetoencephalography study with 45 proficient Spanish-Basque bilinguals, we investigated language selection during covert picture naming and word reading tasks. Participants were prompted to name line drawings or read words if the color of the stimulus changed to green, in 10% of trials. The task was performed either in Spanish or Basque. Despite similar sensor-level evoked activity for both languages in both tasks, decoding analyses revealed language-specific classification ~100 ms post-stimulus onset. During picture naming, right occipital-temporal sensors predominantly contributed to language decoding, while left occipital-temporal sensors were crucial for decoding during word reading. Cross-task decoding analysis unveiled robust generalization effects from picture naming to word reading. Our methodology involved a fine-grained examination of neural responses using magnetoencephalography, offering insights into the dynamics of language processing in bilinguals. This study refines our understanding of the neural underpinnings of language selection and bridges the gap between non-invasive and invasive experimental evidence in bilingual language production.
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Magnetoencefalografia , Multilinguismo , Humanos , Idioma , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Mapeamento Encefálico/métodosRESUMO
Introduction The Boston Naming Test (BNT) is a widely used US neuropsychological evaluation of confrontation naming for the examination of adults and children with learning disabilities and diagnosis of communication disorders, aphasia, dementia, and acquired brain injury or dysfunction. The purpose of the present study is to evaluate the practicality of the original English version of the 60-item BNT (BNT-60) on an Arab population and the need for a new adaptive Arabic version sensitive to cultural biases and to offer normative data that can serve as a reference for researchers and clinicians in the Gulf region, especially the Kingdom of Saudi Arabia (KSA). Data relating to the familiarity degree of the BNT-60 were also collected. Methods This research involved 105 randomly selected and cognitively healthy college students who were native Arabic speakers recruited in Jeddah. The Montreal Cognitive Assessment (MOCA) was administered with a cutoff score of 26. The participants were examined for naming accuracy, naming agreement, and familiarity in using the BNT-60. The data were then analyzed and compared with the findings from studies conducted in the United States. Results The BNT-60 was administered to 105 university students from the KSA, and the results were compared with the BNT-60 booklet norms (second edition). Their average performance was noticeably below the norms established by the original test standards. Compared with the participants in the US studies, the participants made approximately 65% more errors on the items including pretzel, wreath, beaver, harmonica, acorn, stilts, harp, hammock, knocker, pelican, muzzle, unicorn, funnel, accordion, asparagus, tripod, yoke, and trellis and 25% more errors on the items including seahorse, dart, igloo, sphinx, palette, and abacus. The item "boomerang" was not compared with the US sample because of differences in the version of the BNT, but the errors in naming this item were as frequent as those in naming the other misrecognized items. The internal consistency among the items' degrees of familiarity was also very high (α = 0.966), and a significant connection (r = 0.837, P < 0.001) was observed between object familiarity and naming accuracy. The Arabic-speaking population in the KSA and English-speaking population in the United States showed very different levels of familiarity with numerous items. Conclusion The participants' familiarity with the BNT objects varied depending on their culture and impacted their naming accuracy and overall scores on the test. Accordingly, the possibility of cultural biases should be considered when administering the BNT to the population of the KSA and the possibility of making changes so that the test better reflects the Arab culture as suggested.
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Studies of language production often make use of picture naming tasks to investigate the cognitive processes involved in speaking, and many of these studies report a wide range of individual variability in how long speakers need to prepare the name of a picture. It has been assumed that this variability can be linked to inter-individual differences in cognitive skills or abilities (e.g., attention or working memory); therefore, several studies have tried to explain variability in language production tasks by correlating production measures with scores on cognitive tests. This approach, however, relies on the assumption that participants are reliable over time in their picture naming speed (i.e., that faster speakers are consistently fast). The current study explicitly tested this assumption by asking participants to complete a simple picture naming task twice with one to two weeks in between sessions. In one experiment, we show that picture naming speed has excellent within-task reliability and good test-retest reliability, at least when participants perform the same task in both sessions. In a second experiment with slight task variations across sessions (a speeded and non-speeded picture naming task), we replicated the high split-half reliability and found moderate consistency over tasks. These findings are as predicted under the assumption that the speed of initiating responses for speech production is an intrinsic property or capacity of an individual. We additionally discuss the consequences of these results for the statistical power of correlational designs.
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INTRODUCTION: Evidence on the onset of naming deficits in Alzheimer's disease (AD) is mixed. Some studies showed an early decline, but others did not. The present study introduces evidence from a novel naming test. METHODS: Cognitively normal (n = 138), mild cognitive impairment (MCI; n = 21), and Alzheimer's disease (AD; n = 31) groups completed an expanded Multilingual Naming Test with a time-pressured administration procedure (MINT Sprint 2.0). Cerebrospinal fluid biomarkers classified participants as true controls (n = 61) or preclinical AD (n = 26). RESULTS: Total correct MINT Sprint 2.0 scores exhibited good sensitivity and specificity (>0.85) for discriminating true controls from cognitively impaired (MCI/AD) groups and showed significant differences between true controls and preclinical AD groups. Time measurement did not improve classification, but percent resolved scores exhibited promise as an independent AD marker. DISCUSSION: Naming deficits can be detected in the earliest stages of AD with tests and procedures designed for this purpose.
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Doença de Alzheimer , Disfunção Cognitiva , Multilinguismo , Humanos , Doença de Alzheimer/líquido cefalorraquidiano , Disfunção Cognitiva/diagnóstico , Disfunção Cognitiva/líquido cefalorraquidiano , Sensibilidade e Especificidade , Biomarcadores/líquido cefalorraquidiano , Testes NeuropsicológicosRESUMO
While language switching of bilinguals has been investigated extensively in the spoken domain, there has been little research on switching while writing. The factors that impact written language switching may differ from those that impact language switching while speaking. Thus, the study's goal was to test to what extent phonological and/or orthographic overlap impacts written language switching. In four experiments (NExp.1 = 34; NExp. 2 = 57; NExp. 3 = 39; NExp. 4 = 39), German-English bilinguals completed a cued language switching task where responses had to be typed. To-be-named translation-equivalent concepts were selected to be similar phonologically, orthographically or neither. Participants switching between languages while writing was facilitated by both phonological and orthographic overlap. Maximum orthographic overlap between translation-equivalent words with dissimilar pronunciations facilitated switching to the extent that no switch costs could be observed. These results imply that overlapping orthography can strongly facilitate written language switching and that orthography's role should be considered more thoroughly in models of bilingual language production.
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Idioma , Multilinguismo , Humanos , Linguística , Redação , Sinais (Psicologia) , LeituraRESUMO
Though previous studies with autistic individuals have provided behavioral evidence of animacy perception difficulties, the spatio-temporal dynamics of animacy processing in autism remain underexplored. This study investigated how animacy is neurally encoded in autistic adults, and whether potential deficits in animacy processing have cascading deleterious effects on their social functioning skills. We employed a picture naming paradigm that recorded accuracy and response latencies to animate and inanimate pictures in young autistic adults and age- and IQ-matched healthy individuals, while also employing high-density EEG analysis to map the spatio-temporal dynamics of animacy processing. Participants' social skills were also assessed through a social comprehension task. The autistic adults exhibited lower accuracy than controls on the animate pictures of the task and also exhibited altered brain responses, including larger and smaller N100 amplitudes than controls on inanimate and animate stimuli, respectively. At late stages of processing, there were shorter slow negative wave latencies for the autistic group as compared to controls for the animate trials only. The autistic individuals' altered brain responses negatively correlated with their social difficulties. The results suggest deficits in brain responses to animacy in the autistic group, which were related to the individuals' social functioning skills.
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Introduction: The ability to speak is grounded in general memory and control processes and likely changes across the lifespan. However, our knowledge on how word production abilities naturally evolve from childhood to old age remains marginally investigated. Our aim was to shed further light on this issue by exploiting the contrast between two ways to elicit word production: referential picture naming and inferential naming from definition. Methods: We collected accuracy and production latencies in a picture naming task and in a naming from definition task from 130 participants ranging from 10 to 80 years old. Measures of vocabulary size, digit span memory, semantic and phonemic fluencies and processing speed were also collected. We used multivariate adaptative regression splines and regression models to characterize lifespan patterns of the two tasks. Results: Patterns of increase in performance were similar for picture naming and naming from definition only from childhood to young adulthood. In the second half of the lifespan, significant decrease of performance was found in older adults for picture naming (from around 60 years-old) but not for naming from definition. Clearly, word production elicited with an inferential task (naming from definition) yields different age-related patterns than usually described in the literature with a referential task (picture naming). Discussion: We discuss how cognitive processes such as visual-conceptual processes and lexical prediction may explain the differential pattern of results in aging in referential and inferential production tasks. We argue for more lifespan studies and the need to investigate language production beyond picture naming, in particular with respect to aging.
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We present a deep network-based model of the associative memory functions of the hippocampus. The proposed network architecture has two key modules: (1) an autoencoder module which represents the forward and backward projections of the cortico-hippocampal projections and (2) a module that computes familiarity of the stimulus and implements hill-climbing over the familiarity which represents the dynamics of the loops within the hippocampus. The proposed network is used in two simulation studies. In the first part of the study, the network is used to simulate image pattern completion by autoassociation under normal conditions. In the second part of the study, the proposed network is extended to a heteroassociative memory and is used to simulate picture naming task in normal and Alzheimer's disease (AD) conditions. The network is trained on pictures and names of digits from 0 to 9. The encoder layer of the network is partly damaged to simulate AD conditions. As in case of AD patients, under moderate damage condition, the network recalls superordinate words ("odd" instead of "nine"). Under severe damage conditions, the network shows a null response ("I don't know"). Neurobiological plausibility of the model is extensively discussed.