scholarly journals White matter basis for the hub-and-spoke semantic representation: evidence from semantic dementia

Brain ◽  
2020 ◽  
Vol 143 (4) ◽  
pp. 1206-1219 ◽  
Author(s):  
Yan Chen ◽  
Lin Huang ◽  
Keliang Chen ◽  
Junhua Ding ◽  
Yumei Zhang ◽  
...  
Keyword(s):  
White Matter ◽  
Semantic Processing ◽  
Semantic Network ◽  
Semantic Representation ◽  
Semantic Dementia ◽  
Fusiform Gyrus ◽  
Grey Matter Volume ◽  
Hub And Spoke ◽  
Semantic Hub ◽  
General Semantic

Abstract The hub-and-spoke semantic representation theory posits that semantic knowledge is processed in a neural network, which contains an amodal hub, the sensorimotor modality-specific regions, and the connections between them. The exact neural basis of the hub, regions and connectivity remains unclear. Semantic dementia could be an ideal lesion model to construct the semantic network as this disease presents both amodal and modality-specific semantic processing (e.g. colour) deficits. The goal of the present study was to identify, using an unbiased data-driven approach, the semantic hub and its general and modality-specific semantic white matter connections by investigating the relationship between the lesion degree of the network and the severity of semantic deficits in 33 patients with semantic dementia. Data of diffusion-weighted imaging and behavioural performance in processing knowledge of general semantic and six sensorimotor modalities (i.e. object form, colour, motion, sound, manipulation and function) were collected from each subject. Specifically, to identify the semantic hub, we mapped the white matter nodal degree value (a graph theoretical index) of the 90 regions in the automated anatomical labelling atlas with the general semantic abilities of the patients. Of the regions, only the left fusiform gyrus was identified as the hub because its structural connectivity strength (i.e. nodal degree value) could significantly predict the general semantic processing of the patients. To identify the general and modality-specific semantic connections of the semantic hub, we separately correlated the white matter integrity values of each tract connected with the left fusiform gyrus, with the performance for general semantic processing and each of six semantic modality processing. The results showed that the hub region worked in concert with nine other regions in the semantic memory network for general semantic processing. Moreover, the connection between the hub and the left calcarine was associated with colour-specific semantic processing. The observed effects could not be accounted for by potential confounding variables (e.g. total grey matter volume, regional grey matter volume and performance on non-semantic control tasks). Our findings refine the neuroanatomical structure of the semantic network and underline the critical role of the left fusiform gyrus and its connectivity in the network.

scholarly journals At the Edge of Semantic Space: The Breakdown of Coherent Concepts in Semantic Dementia Is Constrained by Typicality and Severity but Not Modality

2011 ◽  
Vol 23 (9) ◽  
pp. 2240-2251 ◽  
Author(s):  
Emily J. Mayberry ◽  
Karen Sage ◽  
Matthew A. Lambon Ralph
Keyword(s):  
Conceptual Knowledge ◽  
Information Sources ◽  
Semantic Representation ◽  
Semantic Space ◽  
Semantic Dementia ◽  
Feature Integration ◽  
Specific Information ◽  
Hub And Spoke ◽  
Invariant Representations ◽  
Multiple Modality

Hub-and-spoke models of semantic representation suggest that coherent concepts are formed from the integration of multiple, modality-specific information sources with additional modality-invariant representations—most likely stored in the ventrolateral anterior temporal lobe (vATL). As well as providing the necessary computational mechanisms for the complexities of feature integration, these modality-invariant representations also license a key aspect of semantic memory—semantic-based generalization. Semantic dementia allows us to investigate this aspect of conceptual knowledge because (a) the patients have a selective and progressive semantic degradation and (b) this is associated with profound ventrolateral ATL atrophy. Specifically, the boundaries between concepts become degraded in semantic dementia and, when tested using the appropriate materials, the patients make simultaneous under- and overgeneralization errors. We found that the rate of these errors were a function of typicality and psuedotypicality of the items as well as the severity of the patients' semantic impairment. Following the modality-invariant nature of the vATL hub representation, we also confirmed that the patients were impaired on both verbal- and picture-based versions of the same task.

The Neural Substrate of Picture Naming

1999 ◽  
Vol 11 (4) ◽  
pp. 399-423 ◽  
Author(s):  
Susan Murtha ◽  
Howard Chertkow ◽  
Mario Beauregard ◽  
Alan Evans
Keyword(s):  
Picture Naming ◽  
Semantic Processing ◽  
Semantic Network ◽  
Cognitive Task ◽  
Judgment Task ◽  
Fusiform Gyrus ◽  
Injection Technique ◽  
Semantic Judgment ◽  
Neural Substrate ◽  
Normal Males

A PET study of 10 normal males was carried out using the bolus H215O intravenous injection technique to examine the effects of picture naming and semantic judgment on blood flow. In a series of conditions, subjects (1) passively viewed flashing plus signs, (2) noted the occurrence of abstract patterns, (3) named animal pictures, or (4) carried out a semantic judgment on animal pictures. Anticipatory scans were carried out after the subjects were presented with the instructions but before they began the cognitive task, as they were passively viewing plus signs. Our results serve to clarify a number of current controversies regarding the neural substrate of picture naming. The results indicate that the fusiform gyrus is unlikely to be the region where low-level perceptual processing such as shape analysis is undertaken. In fact, our evidence suggests that activation of the fusiform gyrus is most likely related to visual perceptual semantic processing. In addition, the inferior/middle frontal lobe activity observed while performing the picture naming and semantic judgment tasks does not appear to be due to the effects of anticipation or preparation. Furthermore, there appears to be a set of regions (a semantic network) that becomes activated regardless of whether the subjects perform a picture naming or semantic judgment task. Finally, picture naming of animals did not activate either parietal regions or anterior inferior left temporal regions, regardless of what subtraction baseline was used.

scholarly journals Modelling the cascade of biomarker changes in GRN-related frontotemporal dementia

2021 ◽  
pp. jnnp-2020-323541
Author(s):  
Jessica L Panman ◽  
Vikram Venkatraghavan ◽  
Emma L van der Ende ◽  
Rebecca M E Steketee ◽  
Lize C Jiskoot ◽  
...  
Keyword(s):  
White Matter ◽  
Frontotemporal Dementia ◽  
Disease Severity ◽  
Grey Matter ◽  
Clinical Stage ◽  
Data Driven ◽  
Grey Matter Volume ◽  
Matter Volume ◽  
Mutation Carriers ◽  
Individual Disease

ObjectiveProgranulin-related frontotemporal dementia (FTD-GRN) is a fast progressive disease. Modelling the cascade of multimodal biomarker changes aids in understanding the aetiology of this disease and enables monitoring of individual mutation carriers. In this cross-sectional study, we estimated the temporal cascade of biomarker changes for FTD-GRN, in a data-driven way.MethodsWe included 56 presymptomatic and 35 symptomatic GRN mutation carriers, and 35 healthy non-carriers. Selected biomarkers were neurofilament light chain (NfL), grey matter volume, white matter microstructure and cognitive domains. We used discriminative event-based modelling to infer the cascade of biomarker changes in FTD-GRN and estimated individual disease severity through cross-validation. We derived the biomarker cascades in non-fluent variant primary progressive aphasia (nfvPPA) and behavioural variant FTD (bvFTD) to understand the differences between these phenotypes.ResultsLanguage functioning and NfL were the earliest abnormal biomarkers in FTD-GRN. White matter tracts were affected before grey matter volume, and the left hemisphere degenerated before the right. Based on individual disease severities, presymptomatic carriers could be delineated from symptomatic carriers with a sensitivity of 100% and specificity of 96.1%. The estimated disease severity strongly correlated with functional severity in nfvPPA, but not in bvFTD. In addition, the biomarker cascade in bvFTD showed more uncertainty than nfvPPA.ConclusionDegeneration of axons and language deficits are indicated to be the earliest biomarkers in FTD-GRN, with bvFTD being more heterogeneous in disease progression than nfvPPA. Our data-driven model could help identify presymptomatic GRN mutation carriers at risk of conversion to the clinical stage.

scholarly journals Age differentiation within grey matter, white matter and between memory and white matter in an adult lifespan cohort

2017 ◽  
Author(s):  
Susanne M. M. de Mooij ◽  
Richard N. A. Henson ◽  
Lourens J. Waldorp ◽  
Cam-CAN ◽  
Rogier A. Kievit
Keyword(s):  
White Matter ◽  
Cognitive Functions ◽  
Structural Equation ◽  
Grey Matter ◽  
Fluid Intelligence ◽  
Cognitive Factors ◽  
Equation Modeling ◽  
Grey Matter Volume ◽  
Adult Lifespan ◽  
Age Related

AbstractIt is well-established that brain structures and cognitive functions change across the lifespan. A longstanding hypothesis called age differentiation additionally posits that the relations between cognitive functions also change with age. To date however, evidence for age-related differentiation is mixed, and no study has examined differentiation of the relationship between brain and cognition. Here we use multi-group Structural Equation Modeling and SEM Trees to study differences within and between brain and cognition across the adult lifespan (18-88 years) in a large (N>646, closely matched across sexes), population-derived sample of healthy human adults from the Cambridge Centre for Ageing and Neuroscience (www.cam-can.org). After factor analyses of grey-matter volume (from T1- and T2-weighted MRI) and white-matter organisation (fractional anisotropy from Diffusion-weighted MRI), we found evidence for differentiation of grey and white matter, such that the covariance between brain factors decreased with age. However, we found no evidence for age differentiation between fluid intelligence, language and memory, suggesting a relatively stable covariance pattern between cognitive factors. Finally, we observed a specific pattern of age differentiation between brain and cognitive factors, such that a white matter factor, which loaded most strongly on the hippocampal cingulum, became less correlated with memory performance in later life. These patterns are compatible with reorganization of cognitive functions in the face of neural decline, and/or with the emergence of specific subpopulations in old age.Significance statementThe theory of age differentiation posits age-related changes in the relationships between cognitive domains, either weakening (differentiation) or strengthening (de-differentiation), but evidence for this hypothesis is mixed. Using age-varying covariance models in a large cross-sectional adult lifespan sample, we found age-related reductions in the covariance among both brain measures (neural differentiation), but no covariance change between cognitive factors of fluid intelligence, language and memory. We also observed evidence of uncoupling (differentiation) between a white matter factor and cognitive factors in older age, most strongly for memory. Together, our findings support age-related differentiation as a complex, multifaceted pattern that differs for brain and cognition, and discuss several mechanisms that might explain the changing relationship between brain and cognition.

scholarly journals Endothelial-derived exosomes demonstrate a link between endothelial innate inflammation and brain dysfunction and injury in aging

2019 ◽  
Author(s):  
F.M. Elahi ◽  
D. Harvey ◽  
M. Altendahl ◽  
K.B. Casaletto ◽  
N. Fernandes ◽  
...  
Keyword(s):  
White Matter ◽  
Human Subjects ◽  
Positive Association ◽  
Regulatory Proteins ◽  
White Matter Injury ◽  
White Matter Hyperintensity ◽  
Grey Matter Volume ◽  
Older Individuals ◽  
Significant Positive Association

ABSTRACTWe test the hypothesis that endothelial cells take on an inflammatory phenotype in functionally intact human subjects with radiographic evidence of white matter injury. Markers within all three complement effector pathways and regulatory proteins were quantified from endothelial-derived exosomes (EDE) of subjects (age 70-82) with (n=11) and without (n=16) evidence of white matter hyperintensity on MRI. Group differences and associations with systemic markers of immune activation (IL6, ICAM1), cognition and neuroimaging were calculated via regression modelling.EDE complement factors within the alternative and classical pathways were found to be higher and regulatory proteins lower in subjects with WMH. EDE levels of several factors demonstrated significant associations with cognitive slowing and systolic blood pressure. The inhibitor of the membrane attack complex, CD46, showed a significant positive association with cerebral grey matter volume. Systemic inflammatory markers, IL6 and ICAM1, were positively associated with EDE levels of several factors.These findings provide the first in vivo evidence of the association of endothelial cell inflammation with white matter injury, cognition, and brain degeneration in functionally normal older individuals, and form the basis for future biomarker development in early or preclinical stages of vascular cognitive impairment and dementia.

Neurochemical profiles of the anterior temporal lobe predict response of repetitive transcranial magnetic stimulation on semantic processing

2021 ◽  
Author(s):  
JeYoung Jung ◽  
Stephen Williams ◽  
Faezeh Sanae Nezhad ◽  
Matthew Lambon Ralph
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Temporal Lobe ◽  
Magnetic Stimulation ◽  
Semantic Processing ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Semantic Representation ◽  
Cortical Region ◽  
Anterior Temporal Lobe ◽  
Neurochemical Profiles

Abstract The effect of repetitive transcranial magnetic stimulation can vary considerably across individuals, but the reasons for this still remain unclear. Here, we investigated whether the response to continuous theta-burst stimulation (cTBS) – an effective protocol for decreasing cortical excitability – related to individual differences in glutamate and GABA neurotransmission. We applied cTBS over the anterior temporal lobe (ATL), a hub for semantic representation, to explore the relationship between the baseline neurochemical profiles in this region and the response to this stimulation. Our experiments revealed that non-responders (subjects who did not show an inhibitory effect of cTBS on subsequent semantic performance) had higher excitatory-inhibitory balance (glutamate + glutamine/GABA ratio) in the ATL, which led to up-regulated task-induced regional activity as well as increased ATL-connectivity with other semantic regions compared to responders. These results disclose that the baseline neurochemical state of a cortical region can be a significant factor in predicting responses to cTBS.

Representation and Display of Digital Images of Cultural Heritage: A Semantic Enrichment Approach

2021 ◽  
Vol 48 (3) ◽  
pp. 231-247
Author(s):  
Xu Tan ◽  
Xiaoxi Luo ◽  
Xiaoguang Wang ◽  
Hongyu Wang ◽  
Xilong Hou
Keyword(s):  
Cultural Heritage ◽  
Digital Images ◽  
Semantic Network ◽  
Semantic Representation ◽  
Semantic Annotation ◽  
Visual Display ◽  
Semantic Content ◽  
Entity Recognition ◽  
Semantic Enrichment ◽  
Fine Grained

Digital images of cultural heritage (CH) contain rich semantic information. However, today’s semantic representations of CH images fail to fully reveal the content entities and context within these vital surrogates. This paper draws on the fields of image research and digital humanities to propose a systematic methodology and a technical route for semantic enrichment of CH digital images. This new methodology systematically applies a series of procedures including: semantic annotation, entity-based enrichment, establishing internal relations, event-centric enrichment, defining hierarchy relations between properties text annotation, and finally, named entity recognition in order to ultimately provide fine-grained contextual semantic content disclosure. The feasibility and advantages of the proposed semantic enrichment methods for semantic representation are demonstrated via a visual display platform for digital images of CH built to represent the Wutai Mountain Map, a typical Dunhuang mural. This study proves that semantic enrichment offers a promising new model for exposing content at a fine-grained level, and establishing a rich semantic network centered on the content of digital images of CH.

scholarly journals Neuroanatomy of Patients with Deficit Schizophrenia: An Exploratory Quantitative Meta-Analysis of Structural Neuroimaging Studies

2020 ◽  
Vol 17 (17) ◽  
pp. 6227 ◽  
Author(s):  
Tji Tjian Chee ◽  
Louis Chua ◽  
Hamilton Morrin ◽  
Mao Fong Lim ◽  
Johnson Fam ◽  
...  
Keyword(s):  
White Matter ◽  
Negative Symptoms ◽  
Meta Analysis ◽  
Regions Of Interest ◽  
Grey Matter Volume ◽  
Healthy Controls ◽  
White Matter Volume ◽  
Total Brain Volume ◽  
Matter Volume ◽  
Deficit Schizophrenia

Little is known regarding the neuroanatomical correlates of patients with deficit schizophrenia or persistent negative symptoms. In this meta-analysis, we aimed to determine whether patients with deficit schizophrenia have characteristic brain abnormalities. We searched PubMed, CINAHL and Ovid to identify studies that examined the various regions of interest amongst patients with deficit schizophrenia, patients with non-deficit schizophrenia and healthy controls. A total of 24 studies met our inclusion criteria. A random-effects model was used to calculate a combination of outcome measures, and heterogeneity was assessed by the I2 statistic and Cochran’s Q statistic. Our findings suggested that there was statistically significant reduction in grey matter volume (−0.433, 95% confidence interval (CI): −0.853 to −0.014, p = 0.043) and white matter volume (−0.319, 95% CI: −0.619 to −0.018, p = 0.038) in patients with deficit schizophrenia compared to healthy controls. There is also statistically significant reduction in total brain volume (−0.212, 95% CI: −0.384 to −0.041, p = 0.015) and white matter volume (−0.283, 95% CI: −0.546 to −0.021, p = 0.034) in patients with non-deficit schizophrenia compared to healthy controls. Between patients with deficit and non-deficit schizophrenia, there were no statistically significant differences in volumetric findings across the various regions of interest.

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