Lexical-semantic Memory Research Articles

Electrical stimulation of the cerebellum facilitates automatic but not controlled word retrieval

Recent research has indicated that the cerebellum is engaged in language functions, yet the role of the cerebellum in lexical-semantic memory is poorly understood. In a double-blind randomized controlled experiment, we therefore targeted the cerebellum by transcranial direct current stimulation (tDCS) to assess and compare the contribution of the cerebellar processing to automatic and controlled retrieval of words in healthy adults (n = 136). Anodal cerebellar tDCS facilitated retrieval of semantically related words in free-associative chains, which was not due to a non-specific acceleration of processing speed. The stimulation had no influence on controlled word retrieval that employed inhibition or switching. The effect of cathodal tDCS was opposite to the anodal stimulation, but statistically non-significant. Our data show that the cerebellum is engaged extracting associative information from the system of semantic representations, established and strengthened/automated by learning, and indicates a domain-general role of this structure in automation of behavior, cognition and language.

Computing word meanings by aggregating individualized distributional models: Wisdom of the crowds in lexical semantic memory

Linguistic experience varies across individuals and is impacted by both demography and personal preferences, leading to differences in word meanings across languages (Thompson et al., 2020) and people (Johns, 2022). An active area of study in the cognitive sciences that examines the impact of varied knowledge across individuals is the wisdom of the crowd effect, where it is found that the aggregate judgement of a group of individuals is often better than the judgement of the best individual in the group (Surowiecki, 2004). The goal of this article was to determine if there is a wisdom of the crowd effect in lexical semantic memory, such that the aggregated word similarity values from many individual language users exceeds the fit of the best fitting individual. This was accomplished by training 500 different distributional models from 500 high-level commenters on the internet forum Reddit. By deriving aggregated word similarity values from these individuals, a strong wisdom of the crowd effect was found where the aggregated similarity values far exceeded the performance of the best fitting individual for each dataset tested. Additionally, it was found that even aggregating only a small number of users provided a large increase in fit relative to the individual corpora, but with the best fitting measure including word similarity values from all possible users. The results of this article provide an avenue for future distributional model development by demonstrating that the best pathway towards better distributional models may lie in the aggregation of multiple representations attained from individual users of a language.

Auditory closure with visual cues: Relationship with working memory and semantic memory

The role of working memory (WM) and long-term lexical-semantic memory (LTM) in the perception of interrupted speech with and without visual cues, was studied in 29 native English speakers. Perceptual stimuli were periodically interrupted sentences filled with speech noise. The memory measures included an LTM semantic fluency task, verbal WM, and visuo-spatial WM tasks. Whereas perceptual performance in the audio-only condition demonstrated a significant positive association with listeners' semantic fluency, perception in audio-video mode did not. These results imply that when listening to distorted speech without visual cues, listeners rely on lexical-semantic retrieval from LTM to restore missing speech information.

Memory enhancement in Argentinian women during postpartum by the dietary intake of lignans and anthocyanins

Due to their polyphenolic content, vegetable foods have neuroprotective effects which provide health benefits for specific human groups. Thus, they may be a useful dietary component for women who experience mnesic variations during postpartum, and here we examined the hypothesis that polyphenols can differentially enhance memory functioning. In particular, we aimed to associate the dietary intake of polyphenols with different memory systems in Argentinian postpartum women. The daily intakes of polyphenol groups were calculated using a validated food frequency questionnaire and the Phenol-Explorer database. Short-term memory (STM), long-term memory (LTM), learning (L), lexical-semantic memory (LSM), and working memory (WM) were assessed. Partial Least Squares (PLS) regression models were used to analyze the dietary polyphenols (predictors) and memory domains (responses), taking into account demographic, obstetric, and psychological factors. The sample included 71 women, with an average age of 29.59 years (SE = 0.73). Most of these women lived in a couple (91%), were unemployed (63%), and had ≥12 years of formal education (72%). STM, LTM, L, and LSM correlated with lignans and anthocyanins, with LTM also being correlated with flavanones, flavonols, and tyrosols, and L and LSM also being associated with flavonols. A significant correlation was also found between WM and lignans. In conclusion, a cognitive improvement was demonstrated, mainly associated with the intake of lignans and anthocyanins, in the STM, LTM, WM, L, and LSM systems of postpartum women. This is the first study to our knowledge suggesting a role of polyphenolic effects on memory functioning during postpartum.

Lexical-semantic and executive deficits revealed by computational modelling: A drift diffusion model perspective

Flexible language use requires coordinated functioning of two systems: conceptual representations and control. The interaction between the two systems can be observed when people are asked to match a word to a picture. Participants are slower and less accurate for related word-picture pairs (word: banana, picture: apple) relative to unrelated pairs (word: banjo, picture: apple). The mechanism underlying interference however is still unclear. We analyzed word-picture matching (WPM) performance of patients with stroke-induced lesions to the left-temporal (N = 5) or left-frontal cortex (N = 5) and matched controls (N = 12) using the drift diffusion model (DDM). In DDM, the process of making a decision is described as the stochastic accumulation of evidence towards a response. The parameters of the DDM model that characterize this process are decision threshold, drift rate, starting point and non-decision time, each of which bears cognitive interpretability. We compared the estimated model parameters from controls and patients to investigate the mechanisms of WPM interference. WPM performance in controls was explained by the amount of information needed to make a decision (decision threshold): a higher threshold was associated with related word-picture pairs relative to unrelated ones. No difference was found in the quality of the evidence (drift rate). This suggests an executive rather than semantic mechanism underlying WPM interference. Both patients with temporal and frontal lesions exhibited both increased drift rate and decision threshold for unrelated pairs relative to related ones. Left-frontal and temporal damage affected the computations required by WPM similarly, resulting in systematic deficits across lexical-semantic memory and executive functions. These results support a diverse but interactive role of lexical-semantic memory and semantic control mechanisms.

The Representation of Coordinate Relations in Lexical Semantic Memory.

Two experiments examined the size of the typicality effect for true items in a category verification task as a function of the type of false item used. In Experiment 1, compared to the case where false items paired unrelated concepts (“carrot–vehicle”), the typicality effect was much larger when false items paired an exemplar with a category coordinate to its proper category (“carrot–fruit”). In contrast, when false items paired coordinate concepts (“carrot–pea”) or reversed the ordering of subject and predicate terms (“All vegetables are carrots”), the typicality effect did not change in size. Further, the time to verify true sentences did not increase monotonically with the semantic similarity of the two terms used in false sentences. Experiment 2 showed that the pattern of results for coordinate items reflected semantic processing, not simply task difficulty. A combined analysis examined data across multiple experiments, increasing the power of the statistical analysis. The size of the typicality effect when coordinate false items were used was again the same as when false items paired unrelated concepts. The most straightforward explanation of this pattern of results seems to be in terms of a sparse semantic network model of lexical semantic memory, in which labeled links are used to indicate the semantic relation that exists between pairs of words.

Altered verbal fluency processes in older adults with age-related hearing loss.

Epidemiological studies have linked age-related hearing loss (ARHL) with an increased risk of neurocognitive decline. Difficulties in speech perception with subsequent changes in brain morphometry, including regions important for lexical-semantic memory, are thought to be a possible mechanism for this relationship. This study investigated differences in automatic and executive lexical-semantic processes on verbal fluency tasks in individuals with acquired hearing loss. The primary outcomes were indices of automatic (clustering/word retrieval at start of task) and executive (switching/word retrieval after start of the task) processes from semantic and phonemic fluency tasks. To extract indices of clustering and switching, we used both manual and computerised methods. There were no differences between groups on indices of executive fluency processes or on any indices from the semantic fluency task. The hearing loss group demonstrated weaker automatic processes on the phonemic fluency task. Further research into differences in lexical-semantic processes with ARHL is warranted.

Weaknesses in Lexical-Semantic Knowledge Among College Students With Specific Learning Disabilities: Evidence From a Semantic Fluency Task.

The purpose of this study is to determine whether deficits in executive function and lexical-semantic memory compromise the linguistic performance of young adults with specific learning disabilities (LD) enrolled in postsecondary studies. One hundred eighty-five students with LD (n = 53) or normal language development (ND, n = 132) named items in the categories animals and food for 1 minute for each category and completed tests of lexical-semantic knowledge and executive control of memory. Groups were compared on total names, mean cluster size, frequency of embedded clusters, frequency of cluster switches, and change in fluency over time. Secondary analyses of variability within the LD group were also conducted. The LD group was less fluent than the ND group. Within the LD group, lexical-semantic knowledge predicted semantic fluency and cluster size; executive control of memory predicted semantic fluency and cluster switches. The LD group produced smaller clusters and fewer embedded clusters than the ND group. Groups did not differ in switching or change over time. Deficits in the lexical-semantic system associated with LD may persist into young adulthood, even among those who have managed their disability well enough to attend college. Lexical-semantic deficits are associated with compromised semantic fluency, and the two problems are more likely among students with more severe disabilities.

Graph-Theoretic Properties of Networks Based on Word Association Norms: Implications for Models of Lexical Semantic Memory.

We compared the ability of three different contextual models of lexical semantic memory (BEAGLE, Latent Semantic Analysis, and the Topic model) and of a simple associative model (POC) to predict the properties of semantic networks derived from word association norms. None of the semantic models were able to accurately predict all of the network properties. All three contextual models over-predicted clustering in the norms, whereas the associative model under-predicted clustering. Only a hybrid model that assumed that some of the responses were based on a contextual model and others on an associative network (POC) successfully predicted all of the network properties and predicted a word's top five associates as well as or better than the better of the two constituent models. The results suggest that participants switch between a contextual representation and an associative network when generating free associations. We discuss the role that each of these representations may play in lexical semantic memory. Concordant with recent multicomponent theories of semantic memory, the associative network may encode coordinate relations between concepts (e.g., the relation between pea and bean, or between sparrow and robin), and contextual representations may be used to process information about more abstract concepts.

What’s in a link: Associative and taxonomic priming effects in the infant lexicon

Infants develop a lexical-semantic system of associatively and semantically related words by the end of the second year of life. However, the precise nature of the lexical relationships that underpin the structure-building process remains under-determined. We compare two types of lexical-semantic relationship, associative and taxonomic, using a lexical-priming adaption of the intermodal preferential looking task with 21- and 24-month-olds. Prime-target word pairs were either associatively or taxonomically related or unrelated. A further control condition evaluated the facility of a prime word, in the absence of a target word, to promote target preferences. Twenty-four-month-olds, but not 21-month-old infants, exhibited a priming effect in both associative and taxonomic conditions, pointing to the formation of a lexical-semantic network driven by both associative and taxonomic relatedness late in the second year. The pattern of priming in 24-month-olds indicates the operation of inhibitory processes: unrelated primes interfere with target recognition whereas related primes do not. We argue that taxonomic and associative relationships between words are integral to the emergence of a structured lexicon and discuss the importance of inhibitory mechanisms in shaping early lexical-semantic memory.

Word Learning in 6-Month-Olds: Fast Encoding–Weak Retention

There has been general consensus that initial word learning during early infancy is a slow and time-consuming process that requires very frequent exposure, whereas later in development, infants are able to quickly learn a novel word for a novel meaning. From the perspective of memory maturation, this shift in behavioral development might represent a shift from slow procedural to fast declarative memory formation. Alternatively, it might be caused by the maturation of specific brain structures within the declarative memory system that may support lexical mapping from the very first. Here, we used the neurophysiological method of ERPs to watch the brain activity of 6-month-old infants, when repeatedly presented with object-word pairs in a cross-modal learning paradigm. We report first evidence that infants as young as 6 months are able to associate objects and words after only very few exposures. A memory test 1 day later showed that infants did not fully forget this newly acquired knowledge, although the ERP effects indicated it to be less stable than immediately after encoding. The combined results suggest that already at 6 months the encoding process of word learning is based on fast declarative memory formation, but limitations in the consolidation of declarative memory diminish the long lasting effect in lexical-semantic memory at that age.

Neural correlates of lexical-semantic memory: A voxel-based morphometry study in mild AD, aMCI and normal aging.

Neuroanatomical correlations of naming and lexical-semantic memory are not yet fully understood. The most influential approaches share the view that semantic representations reflect the manner in which information has been acquired through perception and action, and that each brain area processes different modalities of semantic representations. Despite these anatomical differences in semantic processing, generalization across different features that have similar semantic significance is one of the main characteristics of human cognition.MethodsWe evaluated the brain regions related to naming, and to the semantic generalization, of visually presented drawings of objects from the Boston Naming Test (BNT), which comprises different categories, such as animals, vegetables, tools, food, and furniture. In order to create a model of lesion method, a sample of 48 subjects presenting with a continuous decline both in cognitive functions, including naming skills, and in grey matter density (GMD) was compared to normal young adults with normal aging, amnestic mild cognitive impairment (aMCI) and mild Alzheimer’s disease (AD). Semantic errors on the BNT, as well as naming performance, were correlated with whole brain GMD as measured by voxel-based morphometry (VBM).ResultsThe areas most strongly related to naming and to semantic errors were the medial temporal structures, thalami, superior and inferior temporal gyri, especially their anterior parts, as well as prefrontal cortices (inferior and superior frontal gyri).ConclusionThe possible role of each of these areas in the lexical-semantic networks was discussed, along with their contribution to the models of semantic memory organization.

Italian verb inflection in Alzheimer dementia

A group of 20 patients with probable Alzheimer disease (AD) and a control group were tested in a verb generation task, in a verb synonym task and several cognitive tests. Three types of verbs and novel verbs were presented in simple sentence frames, in two different conditions. In one condition participants were presented with the verb in the infinitive, providing information about the conjugation of the verb and the most likely type of past participle mapping required. The second was an ambiguous condition in which the suffix of the input verb did not provide any clue to the conjugation. The aim was to investigate if different types of verbs and input mapping affected patients’ performance, and to what extent the deficit increased when the illness became more severe. Dependent measures were accuracy rates, rates of different morpho-phonological transformations and error type rates. Patients showed a more marked deficit in verb generation, when input was ambiguous. Correlation between the verb synonym test and accuracy in verb generation indicated that a deficit in lexical–semantic memory was partially responsible for impaired performance. Data suggest that patients maintained information about frequency distribution of different verb types and verb classes in each conjugation, but were impaired in operating complex phonological transformations.

Lexical semantic memory in amnestic mild cognitive impairment and mild Alzheimer's disease

To study lexical semantic memory in patients with amnestic mild cognitive impairment (aMCI), mild Alzheimer's disease (AD) and normal controls. Fifteen mild AD, 15 aMCI, and 15 normal control subjects were included. Diagnosis of AD was based on DSM-IV and NINCDS-ADRDA criteria, and that of aMCI, on the criteria of the International Working Group on Mild Cognitive Impairment, using CDR 0.5 for aMCI and CDR 1 for mild AD. All subjects underwent semantic memory tests (Boston Naming-BNT, CAMCOG Similarities item), Rey Auditory Verbal Learning Test (RAVLT), Mini-Mental Status Examination (MMSE), neuropsychological tests (counterproofs), and Cornell Scale for Depression in Dementia. Data analysis used Mann-Whitney test for intergroup comparisons and Pearson's coefficient for correlations between memory tests and counterproofs (statistical significance level was p<0.05). aMCI patients were similar to controls on BNT and Similarities, but worse on MMSE and RAVLT. Mild AD patients scored significantly worse than aMCI and controls on all tests. aMCI impairs episodic memory but tends to spare lexical semantic system, which can be affected in the early phase of AD.

Are word meanings corresponding to different grammatical categories organised differently within lexical semantic memory?

We report on two experiments that examined lexical semantic memory. Experiment 1 included semantically related word-pairs (similarity of meaning) and unrelated word-pairs from three grammatical categories (nouns, verbs, adjectives). Experiment 2 included semantically related word-pairs (contrasting meaning) and unrelated word-pairs from the same three categories. Results of both experiments showed similar levels of semantic priming across same versus different grammatical category word-pairs (e.g., verb–verb pairs vs. verb–adjective pairs). Additional analyses of each experiment showed similar levels of priming within each of the three grammatical categories (i.e., noun–noun vs. verb–verb vs. adjective–adjective pairs). These findings suggest that there are no sharp architectural distinctions amongst words from different grammatical categories within lexical semantic memory.

Formal thought disorder is characterised by impaired lexical access

Recent studies have proposed that difficulty with accessing the lexical–semantic memory store may underpin some of the specific linguistic problems associated with formal thought disorder (FTD). We examined the consistency of name retrieval as an indicator of the ability to access lexical–semantic knowledge in patients with and without marked FTD to see if problems are specific to the former or common to schizophrenic patients in general. A graded naming test was administered on two separate occasions 8–16 weeks apart to 48 participants in three groups: 16 schizophrenic patients with high ratings of FTD, 16 schizophrenic patients with low ratings of FTD and 16 healthy controls. We compared the groups for naming consistency across time and the relationship between naming consistency and specific symptoms of FTD. Both patient groups had impaired naming and this was significantly greater in high than low FTD patients. The high FTD patients showed a profile that differed from both low FTD patients and healthy controls insofar as their naming was inconsistent across time, characteristic of an access disorder. Specifically, the FTD symptoms of derailment, tangentality and incoherence were related to the ability to access the lexical–semantic store. In conclusion, most patients with schizophrenia show an impaired semantic memory store. Nevertheless, FTD is associated with additional lexical–semantic difficulties that are quantitatively different to those seen in patients without FTD, and which may reflect disorganized semantic access.

Name relearning in elderly patients with schizophrenia: Episodic and temporary, not semantic and permanent

Introduction. Recent reports of lexical-semantic deficits in patients with schizophrenia (Laws, Al-Uzri, & Mortimer, 2000; Laws, McKenna, & Kondel, 1998) suggest that younger patients have problems accessing intact memories and older patients show apparent “loss” of the lexical-semantic memory representations themselves. Methods. Picture naming for everyday items was examined in a unique series of elderly patients with schizophrenia (n = 10) with a mean illness duration of 45.5 years; and compared with that in patients with probable Alzheimer's disease (n = 18) and elderly healthy controls (n = 27). Naming consistency across time was used as an indicator of whether the schizophrenic patients had difficulty accessing representations or a loss of the representations themselves. Finally, we examined the ability of the schizophrenic patients to relearn the names of unnamed items across four weekly retraining sessions and to retain them at a one month follow-up. Results. The elderly schizophrenic patients were as anomic as patients with probable Alzheimer's disease. Consistency analysis revealed that the patients had storage deficits. Analysis of patient error types was consistent with a semantic deficit. Finally, the schizophrenic patients showed significant improvement with relearning, but this was not maintained at follow-up. Conclusions. Elderly patients with schizophrenia show a profound and stable anomia. Although name relearning induced some significant gains in naming, these were short-term and reflect episodic rather than semantic reinstatement of representations. Implications for cognitive remediation are discussed.

P3-30 Altération du traitement phonologique et lexico-sémantique dans l’évolution de la maladie d’Alzheimer : une étude de cas multiples

Flexible language use requires coordinated functioning of two systems: conceptual representations and control. The interaction between the two systems can be observed when people are asked to match a word to a picture. Participants are slower and less accurate for related word-picture pairs (word: banana, picture: apple) relative to unrelated pairs (word: banjo, picture: apple). The mechanism underlying interference however is still unclear. We analyzed word-picture matching (WPM) performance of patients with stroke-induced lesions to the left-temporal (N = 5) or left-frontal cortex (N = 5) and matched controls (N = 12) using the drift diffusion model (DDM). In DDM, the process of making a decision is described as the stochastic accumulation of evidence towards a response. The parameters of the DDM model that characterize this process are decision threshold, drift rate, starting point and non-decision time, each of which bears cognitive interpretability. We compared the estimated model parameters from controls and patients to investigate the mechanisms of WPM interference. WPM performance in controls was explained by the amount of information needed to make a decision (decision threshold): a higher threshold was associated with related word-picture pairs relative to unrelated ones. No difference was found in the quality of the evidence (drift rate). This suggests an executive rather than semantic mechanism underlying WPM interference. Both patients with temporal and frontal lesions exhibited both increased drift rate and decision threshold for unrelated pairs relative to related ones. Left-frontal and temporal damage affected the computations required by WPM similarly, resulting in systematic deficits across lexical-semantic memory and executive functions. These results support a diverse but interactive role of lexical-semantic memory and semantic control mechanisms.

Phonological and Lexical-Semantic Short-Term Memory and their Relationship to Sentence Production in Older Adults

Evidence from brain-damaged patients suggests a link between lexical-semantic retention capacity and sentence production. The present study seeks to establish whether lexical-semantic retention capacity changes with normal aging, and whether individual differences in this capacity predict the degree of increased difficulty older speakers have producing sentences with two-noun initial phrases, relative to those with one-noun initial phrases, elicited in a picture naming task. Older adults performed significantly better than younger adults on one of two tests of lexical-semantic retention, and performed similarly to younger adults on tests of phonological retention. Lexical-semantic capacity, but not phonological capacity, predicted the size of the initial phrase complexity effect in older adults. Results suggest that lexical-semantic retention ability is preserved in normal aging and does play a role in sentence production.

Qualitative aspects of verbal fluency in HIV-associated dementia: a deficit in rule-guided lexical-semantic search processes?

HIV-associated dementia (HAD) is widely considered a “subcortical” dementia that involves a disruption of frontal-basal ganglia circuits. Deficits in verbal fluency are common in HAD; however, the cognitive underpinnings of these deficits are not well understood. To elucidate the cognitive mechanisms underlying the diminished verbal fluency output in HAD, we examined several qualitative aspects of letter fluency in 21 individuals with HAD, 51 nondemented persons with HIV infection (HIV+), and 30 healthy controls (HC) who were comparable for age, education, sex, ethnicity, and estimated premorbid verbal intelligence. The verbal fluency protocols were scored to obtain the total number of correct words, average phonemic cluster size, total number of switches between phonemic clusters, and the proportion of error responses (i.e., intrusions, perseverations, and variants). Consistent with prior research, HAD participants produced significantly fewer total correct words relative to the HC and nondemented HIV+ groups. The HAD group also demonstrated fewer switches and a higher proportion of response errors (especially intrusion errors), but no differences were observed in average cluster size. Findings are interpreted as reflecting a disruption of rule-guided lexical-semantic search strategies in HAD, perhaps mediated by prefrontal-striatal circuit dysfunction, rather than depleted lexical-semantic memory stores.