Organization Of Semantic Memory Research Articles

White matter network underlying semantic processing: evidence from stroke patients.

The hub-and-spoke theory of semantic representation fractionates the neural underpinning of semantic knowledge into two essential components: the sensorimotor modality-specific regions and a crucially important semantic hub region. Our previous study in patients with semantic dementia has found that the hub region is located in the left fusiform gyrus. However, because this region is located within the brain damage in patients with semantic dementia, it is not clear whether the semantic deficit is caused by structural damage to the hub region itself or by its disconnection from other brain regions. Stroke patients do not have any damage to the left fusiform gyrus, but exhibit amodal and modality-specific deficits in semantic processing. Therefore, in this study, we validated the semantic hub region from a brain network perspective in 79 stroke patients and explored the white matter connections associated with it. First, we collected data of diffusion-weighted imaging and behavioural performance on general semantic tasks and modality-specific semantic tasks (assessing object knowledge on form, colour, motion, sound, manipulation and function). We then used correlation and regression analyses to examine the association between the nodal degree values of brain regions in the whole-brain structural network and general semantic performance in the stroke patients. The results revealed that the connectivity of the left fusiform gyrus significantly predicted general semantic performance, indicating that this region is the semantic hub. To identify the semantic-relevant connections of the semantic hub, we then correlated the white matter integrity values of each tract connected to the left fusiform gyrus separately with performance on general and modality-specific semantic processing. We found that the hub region accomplished general semantic processing through white matter connections with the left superior temporal pole, middle temporal gyrus, inferior temporal gyrus and hippocampus. The connectivity between the hub region and the left hippocampus, superior temporal pole, middle temporal gyrus, inferior temporal gyrus and parahippocampal gyrus was differentially involved in object form, colour, motion, sound, manipulation and function processing. After statistically removing the effects of potential confounding variables (i.e. whole-brain lesion volume, lesion volume of regions of interest and performance on non-semantic control tasks), the observed effects remained significant. Together, our findings support the role of the left fusiform gyrus as a semantic hub region in stroke patients and reveal its crucial connectivity in the network. This study provides new insights and evidence for the neuroanatomical organization of semantic memory in the human brain.

Construction of a Hierarchical Organization in Semantic Memory: A Model Based on Neural Masses and Gamma-Band Synchronization

Semantic memory is characterized by a hierarchical organization of concepts based on shared properties. However, this aspect is insufficiently dealt with in recent neurocomputational models. Moreover, in many cognitive problems that exploit semantic memory, gamma-band synchronization can be relevant in favoring information processing and feature binding. In this work, we propose an attractor network model of semantic memory. Each computational unit, coding for a different feature, is described with a neural mass circuit oscillating in the gamma range. The model is trained with an original nonsymmetric Hebb rule based on a presynaptic gating mechanism. After training, the network creates a taxonomy of categories, distinguishes between subordinate and superordinate concepts, and discriminates between salient and marginal features. Examples are provided concerning a fourteen-animal taxonomy, including several subcategories. A sensitivity analysis reveals the robustness of the network but also points out conditions leading to confusion among categories, similar to the one observed in dreaming and some neurological disorders. Finally, the analysis emphasizes the role of fast GABAergic interneurons and inhibitory-excitatory balance to allow the correct synchronization of features. The model represents an original attempt to deal with a hierarchical organization of objects in semantic memory and correlated patterns, still exploiting gamma-band synchronization to favor neural processing. The same ideas, introduced in a more sophisticated multilayer network, can deepen our knowledge of semantic memory organization in the brain. Finally, they can open new perspectives in quantitatively analyzing neurological disorders connected with distorted semantics.

Convergent thinking and insight problem solving relate to semantic memory network structure

The associative theory of creativity has long held that creative thinking involves connecting remote concepts in semantic memory. Network science tools have recently been applied to map the organization of concepts in semantic memory, and to study the link between semantic memory and creativity. Yet such work has largely overlooked the domain of convergent thinking, despite the theoretical importance of semantic memory networks for facilitating associative processes relevant for convergent problem solving (e.g., spreading activation). Convergent thinking problems, such as the Compound Remote Associates (CRA) test, can be solved with insight (the sudden “aha” experience) or analysis (deliberately and incrementally working towards the solution). In a sample of 477 participants, we adopted network science methods to compare semantic memory structure across two grouping variables: 1) convergent thinking ability (i.e., CRA accuracy), and 2) the self-reported tendency to solve problems with insight or analysis. Semantic memory networks were constructed from a semantic fluency task, and problem solving style (insight or analysis) was determined from judgments provided during solving of CRAs. We found that, compared to the low-convergent thinking group, the high-convergent thinking group exhibited a more flexible and interconnected semantic network—with short paths and many connections between concepts. Moreover, participants who primarily solved problems with insight (compared to analysis) showed shorter average path distances between concepts, even after controlling for accuracy. Our results extend the literature on semantic memory and creativity, and suggest that the organization of semantic memory plays a key role in convergent thinking, including insight problem solving.

Encoding of everyday objects in older adults: Episodic memory assessment in virtual reality.

Age-related decline in episodic memory performance in otherwise healthy older adults is indisputably evident. Yet, it has been shown that under certain conditions episodic memory performance in healthy older adults' barely deviates from those seen in young adults. Here we report on the quality of object encoding in an ecologically valid, virtual-reality based memory assessment in a sample of healthy older and younger adults with comparable memory performance. We analyzed encoding by establishing both a serial and semantic clustering index and an object memory association network. As expected, semantic clustering was superior in older adults without need for additional allocation of executive resources whereas young adults tended more to rely on serial strategies. The association networks suggested a plethora of obvious but also less obvious memory organization principles, some of which indicated converging approaches between the groups as suggested by a subgraph analysis and some of which indicated diverging approaches as suggested by the respective network interconnectivity. A higher interconnectivity was observed in the older adults' association networks. We interpreted this as a consequence of superior semantic memory organization (extent to which effective semantic strategies diverged within the group). In conclusion, these results might indicate a diminished need for compensatory cognitive effort in healthy older adults when encoding and recalling everyday objects under ecologically valid conditions. Due to an enhanced and multimodal encoding model, superior crystallized abilities might be sufficient to counteract an age-related decline in various other and specific cognitive domains. This approach might potentially elucidate age-related changes in memory performance in both healthy and pathological aging.

Does adding beer to coffee enhance the activation of drinks? An ERP study of semantic category priming

ABSTRACT Categorization – whether of objects, ideas, or events – is a cognitive process that is essential for human thinking, reasoning, and making sense of everyday experiences. Categorization abilities are typically measured by the Wechsler Adult Intelligence Scale (WAIS) similarity subtest, which consists of naming the shared category of two items (e.g., ‘How are beer and coffee alike’). Previous studies show that categorization, as measured by similarity tasks, requires executive control functions. However, other theories and studies indicate that semantic memory is organized into taxonomic and thematic categories that can be activated implicitly in semantic priming tasks. To explore whether categories can be primed during a similarity task, we developed a double semantic priming paradigm. We measured the priming effect of two primes on a target word that was taxonomically or thematically related to both primes (double priming) or only one of them (single priming). Our results show a larger and additive priming effect in the double priming condition compared to the single priming condition, as measured by both response times and, more consistently, event-related potentials. Our results support the view that taxonomic and thematic categorization can occur during a double priming task and contribute to improving our knowledge on the organization of semantic memory into categories. These findings show how abstract categories can be activated, which likely shapes the way we think and interact with our environment. Our study also provides a new cognitive tool that could be useful to understand the categorization difficulties of neurological patients.

Facilitative Effects of Transcranial Direct Current Stimulation on Semantic Memory Examined by Text-Mining Analysis in Patients With Schizophrenia.

Background: Beneficial effects of transcranial direct current stimulation (tDCS) are relevant to cognition and functional capacity, in addition to psychiatric symptoms in patients with schizophrenia. However, whether tDCS would improve higher-order cognition, e.g., semantic memory organization, has remained unclear. Recently, text-mining analyses have been shown to reveal semantic memory. The purpose of the current study was to determine whether tDCS would improve semantic memory, as evaluated by text-mining analyses of category fluency data, in patients with schizophrenia.Methods: Twenty-eight patients entered the study. Cognitive assessment including the category fluency task was conducted at baseline (before tDCS treatment) and 1 month after t administration of tDCS (2 mA × 20 min, twice per day) for 5 days, according to our previous study. The category fluency data were also obtained from 335 healthy control subjects. The verbal outputs (i.e., animal names) from the category fluency task were submitted to singular valued decomposition (SVD) analysis. Semantic memory structures were estimated by calculating inter-item cosines (i.e., similarities) among animal names frequently produced in the category fluency task. Data were analyzed longitudinally and cross-sectionally to compare the semantic structure within the patient group (i.e., baseline vs. follow-up) and between groups (patients vs. healthy controls). In the former, semantic associations for frequent items were compared in the form of cosine profiles, while in the latter, the difference in the magnitude of the correlations for inter-item cosines between healthy controls and patients (baseline, follow-up) was examined.Results: Cosine profiles in the patient group became more cluster-based (i.e., pet, carnivores, and herbivores) at follow-up compared to those at baseline, yielding higher cosines within subcategories. The correlational coefficient of inter-item cosines between healthy controls and patients was significantly greater at follow-up compared to baseline; semantic associations in patients approached the normality status after multi-session tDCS.Conclusions: To our knowledge, this is the first study to demonstrate the facilitative effect of tDCS on semantic memory organization in patients with schizophrenia. Text-mining analysis was indicated to effectively evaluate semantic memory structures in patients with psychiatric disorders.

Revealing the Role of Divergent Thinking and Fluid Intelligence in Children's Semantic Memory Organization.

The current theories suggest the fundamental role of semantic memory in creativity, mediating bottom-up (divergent thinking) and top-down (fluid intelligence) cognitive processes. However, the relationship between creativity, intelligence, and the organization of the semantic memory remains poorly-characterized in children. We investigated the ways in which individual differences in children’s semantic memory structures are influenced by their divergent thinking and fluid intelligence abilities. The participants (mean age 10) were grouped by their levels (high/low) of divergent thinking and fluid intelligence. We applied a recently-developed Network Science approach in order to examine group-based semantic memory graphs. Networks were constructed from a semantic fluency task. The results revealed that divergent thinking abilities are related to a more flexible structure of the semantic network, while fluid intelligence corresponds to a more structured semantic network, in line with the previous findings from the adult sample. Our findings confirm the crucial role of semantic memory organization in creative performance, and demonstrate that this phenomenon can be traced back to childhood. Finally, we also corroborate the network science methodology as a valid approach to the study of creative cognition in the developmental population.

Multimodal semantic battery to monitor progressive loss of concepts in the semantic variant of primary progressive aphasia (svPPA): an innovative proposal

ABSTRACT Semantic variant primary progressive aphasia (svPPA) is a rare neurodegenerative disease characterized by a progressive loss of semantic knowledge. Patients with svPPA show anomia, impaired word comprehension, poor object recognition, and difficulties in retrieving semantic information. svPPA is also a unique “natural” model that allows clinicians and cognitive neuroscientists to study the organization of semantic memory because only semantic knowledge is affected in the initial period of the disease, with relative sparing of other cognitive domains. In the clinical practice, semantic memory is commonly tested only with verbal tests. The aim of the present study was to preliminary test a new Multimodal Semantic Battery developed in our laboratory, which comprised 11 subtests designed to assess the semantic knowledge of multiple items via all input modalities. The battery was administered twice, over four years, to a patient diagnosed with svPPA. We found that when extensively tested with multiple tests, in some cases, he was still able to recall semantic features of the items that otherwise would not have emerged with standard semantic tests. These results are discussed for the clinical practice: monitoring semantic memory through all modalities in a practical and reliable way could be useful for both clinicians and experimental researchers to better investigate the breakdown of semantic knowledge.

M66. FACILITATIVE EFFECTS OF TRANSCRANIAL DIRECT CURRENT STIMULATION ON SEMANTIC MEMORY EXAMINED BY TEXT-MINING ANALYSIS IN PATIENTS WITH SCHIZOPHRENIA

BackgroundTranscranial direct current stimulation (tDCS) is a neurophysiological therapy which modulates neural activities in the brain with weak electrical current. The beneficial effects of tDCS are relevant to positive and negative symptoms, as well as cognition and functional capacity in patients with schizophrenia (Narita et al, 2017). However, whether tDCS would improve higher-order cognition, e.g. semantic memory organization, has remained unclear. Recently, text-mining analyses have been proven to be effective to reveal semantic memory in patients with schizophrenia (Sung et al., 2012; Sumiyoshi et al., 2018). The purpose of the study was to investigate effects of tDCS to improve semantic memory, as evaluated by text-mining analyses of category fluency data, in patients with schizophrenia.MethodsTwenty-eight patients meeting DSM-5 criteria for schizophrenia entered the study. All subjects gave written informed consent, and the study was approved by the Ethical Committee of National Center of Neurology and Psychiatry and the Ethical Committee of Osaka university. Data from healthy control subjects (N=335) were also used. The tDCS was conducted according to the previous study (Narita et al., 2017). tDCS was administered twice a day in 5 consecutive days. The Brief Assessment of Cognition in Schizophrenia, (BACS) was administered at baseline and one month after the last tDCS session. Verbal outputs of the category fluency task in the BACS were submitted to the singular valued decomposition (SVD) analysis. Semantic memory structures were estimated by calculating cosine values (i.e. similarities) among frequent items in the six-dimensional solution. These values were compared between healthy controls vs. patients at baseline and follow-up using Pearson’s correlational coefficients.ResultsThe correlational coefficient for the frequent items (DOG, CAT, ELEPAHANT, GIRAFFE, LION, TIGER) between patients and healthy controls was considerably higher at the follow-up (r=0.58) compared to that at base line (r=0.12), reaching a marginal significance (p=0.058). A visual inspection for the cosine profiles of frequent items indicated that distinct clusters of Pet (DOG, CAT), Wild-Herbivorous (ELEPAHANT, GIRAFFE), and Wild-Carnivorous (LION, TIGER) in patients at follow-up, as in the case for healthy controls.DiscussionTo our knowledge, this is the first study reporting a facilitative effect of tDCS on higher-order of cognition in patients with schizophrenia. Semantic memory in the patients became structurally similar to that for healthy controls after administration of tDCS. Furthermore, animal names frequently produced were meaningfully clustered in patients at follow-up, similar to the pattern of healthy controls. These results may explain the efficacy of tDCS for improving other domains of cognitive function in patients with schizophrenia. We also could demonstrate that text-mining analysis is a powerful tool to elucidate higher-order cognition in people with mental disorders.ReferencesNarita, Z et al. 2017a. Front. Psychiatry, 8:184. doi: 10.3389/fpsyt.2017.00184.Sung, K. et al. 2012. J Int Neuropsychol Soc.,18, 565-57Sumiyoshi, C. et al. 2018. Front. Psychiatry, 9:87. doi: 10.3389/fpsyt.2018.00087

An Analysis of Famous Person Semantic Memory in Aging

ABSTRACTBackground: In contrast to most memory systems that decline with age, semantic memory tends to remain relatively stable across the life span. However, what exactly is stable remains unclear. Is it the quantity of information available or the organization of semantic memory, i.e., the connections between semantic items? Even less is known about semantic memory for celebrities, a subsystem of semantic memory. In the present study, we studied the organization of person-specific semantic memory and its stability in aging.Methods: We designed a word association task based on a previous study, which consisted in providing the first word that came to the mind of the participants (15 participants for each age group 20–30, 40–50 and 60–70 years old) for 144 celebrities. We developed a new taxonomy of associated responses as the responses associated with celebrities name could in principle be very varied.Results: We found that most responses (>90%) could be grouped into five categories (subjective; superordinate general; superordinate specific; imagery and activities). The elderly group did not differ from the other two groups in term of errors or reaction time suggesting they performed the task well. However, they also provided associations that were less precise and less based on imagery. In contrast, the middle-age group provided the most precise associations.Conclusion: These results support the idea of a durable person-specific semantic memory in aging but show changes in the type of associations that elders provide. Future work should aim at studying patients with early semantic impairment, as they could be different from the healthy elders on such semantic association task.

How taxonomic and thematic associations in semantic memory modulate recall in young through old-old adults.

The aim of the current study was to investigate how the taxonomic and thematic organization of semantic long-term memory affected the recall performance of adults and older participants on a complex semantic working memory (SWM) task. Taxonomic and thematic classification are the two main systems used to organize knowledge: taxonomic information is hierarchically structured and typically independent of space and time, whereas thematically grouped concepts are horizontal and strictly context-dependent. Generally, thematic connections (more intuitive and experience-based) are formed earlier in development, while taxonomic links (more abstract and logic-based) are acquired later. We set out to explore whether this developmental pattern reverses with age, hypothesizing that the more complex form of memory organization (i.e., taxonomic) would play a lesser role in facilitating recall in the old, whereas thematic organization would be better preserved. Participants (aged 18 to 85 years) were asked to recall 60 words in sets of increasing span; the words were featured in lists organized to force a taxonomic association, a thematic association, or no semantic association. The results clearly showed that task accuracy varied more across age groups for taxonomically linked items than for thematically linked ones. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

A feature-based neurocomputational model of semantic memory.

According with a featural organization of semantic memory, this work is aimed at investigating, through an attractor network, the role of different kinds of features in the representation of concepts, both in normal and neurodegenerative conditions. We implemented new synaptic learning rules in order to take into account the role of partially shared features and of distinctive features with different saliency. The model includes semantic and lexical layers, coding, respectively for object features and word-forms. Connections among nodes are strongly asymmetrical. To account for the feature saliency, asymmetrical synapses were created using Hebbian rules of potentiation and depotentiation, setting different pre-synaptic and post-synaptic thresholds. A variable post-synaptic threshold, which automatically changed to reflect the feature frequency in different concepts (i.e., how many concepts share a feature), was used to account for partially shared features. The trained network solved naming tasks and word recognition tasks very well, exploiting the different role of salient versus marginal features in concept identification. In the case of damage, superordinate concepts were preserved better than the subordinate ones. Interestingly, the degradation of salient features, but not of marginal ones, prevented object identification. The model suggests that Hebbian rules, with adjustable post-synaptic thresholds, can provide a reliable semantic representation of objects exploiting the statistics of input features.

Remotely Close Associations: Openness to Experience and Semantic Memory Structure

Openness to experience—the enjoyment of novel experiences and ideas—has many connections to cognitive processes. People high in openness to experience, for example, tend to be more creative and have broader general knowledge than people low in openness to experience. In the current study, we use a network science approach to examine if the organization of semantic memory differs between high and low groups of openness to experience. A sample of 516 adults completed measures of openness to experience (from the NEO Five–Factor Inventory–3 and Big Five Aspect Scales) and a semantic verbal fluency task. Next, the sample was split into half to form high ( n = 258) and low ( n = 258) openness to experience groups. Semantic networks were then constructed on the basis of their verbal fluency responses. Our results revealed that the high openness to experience group's network was more interconnected, flexible, and had better local organization of associations than the low openness to experience group. We also found that the high openness to experience group generated more responses on average and provided more unique responses than the low openness to experience group. Taken together, our results indicate that openness to experience is related to semantic memory structure. © 2018 European Association of Personality Psychology

How experience modulates semantic memory for food: evidence from elderly adults and centenarians

In order to make sense of the objects we encounter in everyday life we largely rely on previous knowledge stored in our semantic memory. Semantic memory is considered dependent on lifelong experience and cultural knowledge. So far, a few studies have investigated the role of expertise on the organization of semantic memory, whereas life-long experience has largely been overlooked. In this study, we investigated this issue using food concepts. In particular, we administered different semantic tasks using food (natural and transformed) and non-food (living and non-living things) as stimuli to participants belonging to three different age cohorts (56–74, 75–91, 100–108), who were also asked to report on the dietary habits held throughout their life. In addition, we investigated to what extent psycholinguistic variables influence the semantic performance of different age cohorts. Results showed that Centenarians recognized natural food better than transformed food, while the other two groups showed the opposite pattern. According to our analyses, experience is responsible for this effect in Centenarians, as their dietary habits seem to suggest. Moreover, significant correlations between picture naming and age of acquisition, familiarity and frequency were observed. This study indicates that lifelong experience can shape conceptual knowledge of food concepts, and that semantic memory is less resilient to aging than initially thought.

Semantic Memory Organization in Japanese Patients With Schizophrenia Examined With Category Fluency.

Disorganization of semantic memory in patients with schizophrenia has been studied by referring to their category fluency performance. Recently, data-mining techniques such as singular value decomposition (SVD) analysis have been reported to be effective in elucidating the latent semantic memory structure in patients with schizophrenia. The aim of this study is to investigate semantic memory organization in patients with schizophrenia using a novel method based on data-mining approach. Category fluency data were collected from 181 patients with schizophrenia and 335 healthy controls at the Department of Psychiatry, Osaka University. The 20 most frequently reported animals were chosen for SVD analysis. In the two-dimensional (2D) solution, item vectors (i.e., animal names) were plotted in the 2D space of each group. In the six-dimensional (6D) solution, inter-item similarities (i.e., cosines) were calculated among items. Cosine charts were also created for the six most frequent items to show the similarities to other animal items. In the 2D spatial representation, the six most frequent items were grouped in the same clusters (i.e., dog, cat as pet cluster, lion, tiger as wild/carnivorous cluster, and elephant, giraffe as wild/herbivorous cluster) for patients and healthy adults. As for 6D spatial cosines, the correlations (Pearson's r) between 17 items commonly generated in the two groups were moderately high. However, cosine charts created for the three pairs from the six most frequent animals (dog-cat, lion-tiger, elephant-giraffe) showed that pair-wise similarities between other animals were less salient in patients with schizophrenia. Semantic memory organization in patients with schizophrenia, revealed by SVD analysis, did not appear to be seriously impaired in the 2D space representation, maintaining a clustering structure similar to that in healthy controls for common animals. However, the coherence of those animals was less salient in 6D space, lacking pair-wise similarities to other members of the animal category. These results suggests subtle but structural differences between the two groups. A data-mining approach by means of SVD analysis seems to be effective in evaluating semantic memory in patients with schizophrenia, providing both a visual representation and an objective measure of the structural alterations.

Exploring the Organization of Semantic Memory through Unsupervised Analysis of Event-related Potentials.

Modern multivariate methods have enabled the application of unsupervised techniques to analyze neurophysiological data without strict adherence to predefined experimental conditions. We demonstrate a multivariate method that leverages priming effects on the evoked potential to perform hierarchical clustering on a set of word stimuli. The current study focuses on the semantic relationships that play a key role in the organization of our mental lexicon of words and concepts. The N400 component of the event-related potential is considered a reliable neurophysiological response that is indicative of whether accessing one concept facilitates subsequent access to another (i.e., one "primes" the other). To further our understanding of the organization of the human mental lexicon, we propose to utilize the N400 component to drive a clustering algorithm that can uncover, given a set of words, which particular subsets of words show mutual priming. Such a scheme requires a reliable measurement of the amplitude of the N400 component without averaging across many trials, which was here achieved using a recently developed multivariate analysis method based on beamforming. We validated our method by demonstrating that it can reliably detect, without any prior information about the nature of the stimuli, a well-known feature of the organization of our semantic memory: the distinction between animate and inanimate concepts. These results motivate further application of our method to data-driven exploration of disputed or unknown relationships between stimuli.

What is semantic in semantic dementia? The decay of knowledge of physical entities but not of verbs, numbers and body parts

ABSTRACTBackground: Conceptual knowledge does not decay randomly in patients with cerebral damage, suggesting that dedicated neural substrates may support different categories of knowledge. Semantic dementia is an optimal natural model for studying the organization of semantic memory. Nevertheless, in a pathology primarily characterized by a semantic memory disorder categorical- and modality- specific effects are not obvious findings. In fact, there is no clear evidence of categorical effects, at least concerning two broad categories of knowledge, that is, natural items and artifacts. Furthermore, transmodal deficits do not seem to be the rule in SD. Also quite robust is the observation that some conceptual domains are relatively spared in this pathology, that is, numerical knowledge, abstract words, and action verbs.Aims: To explore category specific and modality specific deficit in SD and to support the evidence that semantic degradation in SD primarily involves knowledge of the objects in the real world, whereas categories of knowledge whose items can be less easily identified by surface attributes, such as verbs, numbers and body parts, are more preserved.Methods and Procedures: We investigated the semantic impairment in 8 patients with Semantic Dementia (SD). Voxel-based morphometry (VBM) in each patient was also obtainedOutcomes and Results: In some patients manmade objects were significantly more preserved than natural items, verbs more preserved than nouns and the number system entirely preserved; the body parts category was the least impaired in all subjects; finally, in three patients visual semantic knowledge was significantly more preserved than verbal semantic knowledge. VBM showed that atrophy of the anterior inferior temporal regions was insufficient to impair knowledge about verbs, numbers and body parts, whose impairment was associated with more widespread atrophy. In subjects whose verbal semantic knowledge was significantly more impaired than visual semantic knowledge, atrophy was principally distributed in the left hemisphere. In patients with significant impairment for natural items compared to manmade objects, atrophy was not confine in the temporal lobes.Conclusion: We conclude that in SD semantic decay primarily involves the real-world items whose knowledge is processed by surface sensorifunctional features and that this is the type of knowledge stored in the temporal lobes. Our data support a model that associates a semantic hub with modality/category specific neural substrates.

Action Categories in Lateral Occipitotemporal Cortex Are Organized Along Sociality and Transitivity

How neural specificity for distinct conceptual knowledge categories arises is central for understanding the organization of semantic memory in the human brain. Although there is a large body of research on the neural processing of distinct object categories, the organization of action categories remains largely unknown. In particular, it is unknown whether different action categories follow a specific topographical organization on the cortical surface analogously to the category-specific organization of object knowledge. Here, we tested whether the neural representation of action knowledge is organized in terms of nonsocial versus social and object-unrelated versus object-related actions (sociality and transitivity, respectively, hereafter). We hypothesized a major distinction of sociality and transitivity along dorsal and ventral lateral occipitotemporal cortex (LOTC), respectively. Using fMRI-based multivoxel pattern analysis, we identified neural representations of action information associated with sociality and transitivity in bilateral LOTC. Representational similarity analysis revealed a dissociation between dorsal and ventral LOTC. We found that action representations in dorsal LOTC are segregated along features of sociality, whereas action representations in ventral LOTC are segregated along features of transitivity. In addition, representations of sociality and transitivity features were found more anteriorly in LOTC than representations of specific subtypes of actions, suggesting a posterior–anterior gradient from concrete to abstract action features. These findings elucidate how the neural representations of perceptually and conceptually diverse actions are organized in distinct subsystems in the LOTC. <b>SIGNIFICANCE STATEMENT</b> The lateral occipitotemporal cortex (LOTC) is critically involved in the recognition of objects and actions, but our knowledge about the underlying organizing principles is limited. Here, we discovered a dorsal–ventral distinction of actions in LOTC: dorsal LOTC represents actions based on sociality (how much an action is directed to another person) in proximity to person knowledge. In contrast, ventral LOTC represents actions based on transitivity (how much an action involves the interaction with inanimate objects) in proximity to tools/artifacts in ventral LOTC, suggesting a mutually dependent organization of actions and objects. In addition, we found a posterior-to-anterior organization of the LOTC for concrete and abstract representations, respectively. Our findings provide important insights about the organization of actions in LOTC.

Применение методологии искусственного интеллекта для формализации результатов обработки нечеткой информации

One of the distinctive features pertinent to the present-day conditions under which the power plant equipment operate is the necessity to run it in variable modes, as a result of which certain changes occur in the equipment technical state with time. These factors have generated the need of solving, on a priority basis, a number of unresolved matters concerned with creating models for decision-making and state recognition proceeding from power plant diagnostics with the use of fuzzy information for identifying the equipment state and managing the equipment recovering processes. It should be noted, however, that there is no unified methodological approach to obtaining the relevant information for diagnostic purposes in solving such problems under the conditions of fuzziness and inhomogeneity of initial information about the actual equipment state and its residual life. As a result, the existing methods for shaping data and knowledge in performing an analysis of data and in making managerial decisions are not identified and are not interconnected with their mathematical models. In addition, they are aimed at solving separate tasks and are not always able to ensure that the equipment set model’s parameters are consistent with the actual state of the facility in question. At the same time, the shift that was done in the power industry from the policy of planned and preventive repairs to the policy of repairs according to the actual technical state has resulted in that a higher responsibility has to be undertaken by those who make decisions in determining the repair scope and timeframes, and, accordingly, more stringent requirements are imposed on the quality of diagnostic models. As a consequence of its having been made without doing proper methodical background work, such a shift has lead a situation in which the diagnostic and the decision-making models turned to be inadequate due to the use of information about the equipment state that contains uncertainties. At the same time, recent years have seen a drastically grown interest in various aspects of the intellectual management problem, in particular, the intellectual management by technologies according to a hybrid principle. One of the main areas involves the use of techniques developed within the framework of fuzzy systems and cognitive neural sciences: fuzzy sets, fuzzy logic, fuzzy modeling and management, semantic memory organization, fuzzy mathematics, artificial neural networks, pattern recognition, data processing by human neurons and brain, human consciousness, mind, memory, and artificial life. The article presents the results from extending the range of practical applications of the fuzzy and hybrid system techniques as applied to the technologies of estimating the state of complex technical systems (including power systems), especially under the conditions of data processing and using cognitive neural sciences.

Fonctions cognitives sous-jacentes aux déficits de fluence verbale dans la schizophrénie : revue de la littérature

Individuals with schizophrenia usually show impairment on various cognitive functions, including long-term memory, executive functions and language. Compared to healthy controls, their performance is impaired in verbal fluency tests. These tests require participants to generate in a given time as many words as they can, belonging to a given category (semantic fluency), or beginning with a specific letter (orthographic fluency). Various cognitive functions are involved in verbal fluency tests: psychomotor speed, executive functions, language, long-term verbal memory and semantic memory. The purpose of the present study was to clarify the functional origin of verbal fluency deficits in schizophrenia through a literature review. Nineteen articles were selected in Pubmed and PsycINFO after initial screening and detailed review. They were formally analyzed with regard to general performance, cognitive strategies used in semantic and orthographic fluency tests and, underlying cognitive origin of deficits. Results show that individuals with schizophrenia produce fewer words than healthy controls in both types of fluency tests. Their impairment is more apparent in semantic than in orthographic fluency tests. Results of studies reviewed also show that individuals with schizophrenia adopt the same clustering (i.e. production of related words within a subcategory) and switching (i.e. ability to shift between clusters when a subcategory is exhausted) strategies than healthy controls, but less efficiently. Several hypotheses, such as the impairment of executive functions, semantic memory or speed of information processing, were put forward to account for this finding. Interestingly, the few studies in which researchers performed an analysis of the semantic relationships between words produced in fluency tests showed a less semantic coherence among people with schizophrenia than in healthy controls. Such a difference could be explained by disorganization of semantic memory or impairment in the activation of conceptual representations in semantic memory. Studies in which correlations and regression analyzes were performed allow for clarifying the cognitive origin underlying verbal fluency deficits in schizophrenia. The links between these deficits and information processing speed as well as working memory are well established. These two cognitive domains also appear to be strong predictors of performance in semantic and orthographic fluency tasks in schizophrenia. Individuals with schizophrenia usually present with a significant slowdown in the speed of information processing. Such a slowdown is likely to account for their poor performance in verbal fluency tests, which require the independent and rapid production of words. Working memory disorders are also core cognitive symptoms of schizophrenia. Working memory is involved in verbal fluency tests since they involve “strategic” activation of verbal information in long-term memory, inhibition of inappropriate words, switching between clusters, etc. However, the concept of working memory also partially encompasses the notion of executive functions so that the results reported in the present literature review, according to which impairment of verbal fluency in schizophrenia results from working memory deficits but not from executive functions deficits, are difficult to interpret. Results are also less clear-cut in regard to verbal long-term memory and to language abilities. Finally, numerous studies had shown that individuals with schizophrenia present specific deficits in the organization of semantic memory. However, the impact of this deficit on verbal fluency was explored in one study only. To conclude, verbal fluency tests are sensitive to various neurocognitive conditions and are helpful for differential diagnosis. Further studies are still needed to clarify the functional origin of verbal fluency deficits in schizophrenia, in particular the differential role of executive functions and working memory as well as the impact of semantic memory impairment.