scholarly journals Disordered semantic representation in schizophrenic temporal cortex revealed by neuromagnetic response patterns

2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Andreas Löw ◽  
Brigitte Rockstroh ◽  
Thomas Elbert ◽  
Yaron Silberman ◽  
Shlomo Bentin
2016 ◽  
Author(s):  
Samuel A. Nastase ◽  
Andrew C. Connolly ◽  
Nikolaas N. Oosterhof ◽  
Yaroslav O. Halchenko ◽  
J. Swaroop Guntupalli ◽  
...  

AbstractHumans prioritize different semantic qualities of a complex stimulus depending on their behavioral goals. These semantic features are encoded in distributed neural populations, yet it is unclear how attention might operate across these distributed representations. To address this, we presented participants with naturalistic video clips of animals behaving in their natural environments while the participants attended to either behavior or taxonomy. We used models of representational geometry to investigate how attentional allocation affects the distributed neural representation of animal behavior and taxonomy. Attending to animal behavior transiently increased the discriminability of distributed population codes for observed actions in anterior intraparietal, pericentral, and ventral temporal cortices. Attending to animal taxonomy while viewing the same stimuli increased the discriminability of distributed animal category representations in ventral temporal cortex. For both tasks, attention selectively enhanced the discriminability of response patterns along behaviorally relevant dimensions. These findings suggest that behavioral goals alter how the brain extracts semantic features from the visual world. Attention effectively disentangles population responses for downstream read-out by sculpting representational geometry in late-stage perceptual areas.


2019 ◽  
Author(s):  
Steven M Frankland ◽  
Joshua D. Greene

To understand a simple sentence such as “the woman chased the dog”, the human mind must dynamically organize the relevant concepts to represent who did what to whom. This structured re-combination of concepts (woman, dog, chased) enables the representation of novel events, and is thus a central feature of intelligence. Here, we use fMRI and encoding models to delineate the contributions of three brain regions to the representation of structured, relational combinations. We identify a region of rostral-medial prefrontal cortex (rmPFC) that shares representations of noun-verb conjunctions across sentences: for example, combining “woman” and “chased” to encode woman-as-chaser, distinct from woman-as-chasee. This PFC region differs from the left-mid superior temporal cortex (lmSTC) and hippocampus, two regions previously implicated in representing relations. lmSTC represents broad role combinations that are shared across verbs (e.g., woman-as-agent), rather than narrow roles, limited to specific actions (woman-as-chaser). By contrast, a hippocampal sub-region represents instances of recurring noun-verb conjunctions as dissimilar to one another, and is anti-correlated with rMPFC on a trial-by-trial basis, consistent with a pattern separation mechanism. These three regions appear to play distinct, but complementary, roles in encoding compositional event structure.


2007 ◽  
Vol 104 (51) ◽  
pp. 20600-20605 ◽  
Author(s):  
N. Kriegeskorte ◽  
E. Formisano ◽  
B. Sorger ◽  
R. Goebel

2019 ◽  
Author(s):  
Paul Hoffman ◽  
Andres Tamm

AbstractHomonyms are a critical test case for investigating how the brain resolves ambiguity in language and, more generally, how context influences semantic processing. Previous neuroimaging studies have associated processing of homonyms with greater engagement of regions involved in executive control of semantic processing. However, the precise role of these areas and the involvement of semantic representational regions in homonym comprehension remain elusive. We addressed this by combining univariate and multivariate fMRI analyses of homonym processing. We tested whether multi-voxel activation patterns could discriminate between presentations of the same homonym in different contexts (e.g., bark following tree vs. bark following dog). The ventral anterior temporal lobe, implicated in semantic representation but not previously in homonym comprehension, showed this meaning-specific coding, despite not showing increased mean activation for homonyms. Within inferior frontal gyrus (IFG), a key site for semantic control, there was a dissociation between pars orbitalis, which also showed meaning-specific coding, and pars triangularis, which discriminated more generally between semantically related and unrelated word pairs. IFG effects were goal-dependent, only occurring when the task required semantic decisions, in line with a top-down control function. Finally, posterior middle temporal cortex showed a hybrid pattern of responses, supporting the idea that it acts as an interface between semantic representations and the control system. The study provides new evidence for context-dependent coding in the semantic system and clarifies the role of control regions in processing ambiguity. It also highlights the importance of combining univariate and multivariate neuroimaging data to fully elucidate the role of a brain region in semantic cognition.


2020 ◽  
Author(s):  
D. Proklova ◽  
M.A. Goodale

AbstractAnimate and inanimate objects elicit distinct response patterns in the human ventral temporal cortex (VTC), but the exact features driving this distinction are still poorly understood. One prominent feature that distinguishes typical animals from inanimate objects and that could potentially explain the animate-inanimate distinction in the VTC is the presence of a face. In the current fMRI study, we investigated this possibility by creating a stimulus set that included animals with faces, faceless animals, and inanimate objects, carefully matched in order to minimize other visual differences. We used both searchlight-based and ROI-based representational similarity analysis (RSA) to test whether the presence of a face explains the animate-inanimate distinction in the VTC. The searchlight analysis revealed that when animals with faces were removed from the analysis, the animate-inanimate distinction almost disappeared. The ROI-based RSA revealed a similar pattern of results, but also showed that, even in the absence of faces, information about agency (a combination of animal’s ability to move and think) is present in parts of the VTC that are sensitive to animacy. Together, these analyses showed that animals with faces do elicit a stronger animate/inanimate response in the VTC, but that this effect is driven not by faces per se, or the visual features of faces, but by other factors that correlate with face presence, such as the capacity for self-movement and thought. In short, the VTC appears to treat the face as a proxy for agency, a ubiquitous feature of familiar animals.Significance StatementMany studies have shown that images of animals are processed differently from inanimate objects in the human brain, particularly in the ventral temporal cortex (VTC). However, what features drive this distinction remains unclear. One important feature that distinguishes many animals from inanimate objects is a face. Here, we used fMRI to test whether the animate/inanimate distinction is driven by the presence of faces. We found that the presence of faces did indeed boost activity related to animacy in the VTC. A more detailed analysis, however, revealed that it was the association between faces and other attributes such as the capacity for self-movement and thinking, not the faces per se, that was driving the activity we observed.


2016 ◽  
Vol 28 (3) ◽  
pp. 351-360 ◽  
Author(s):  
Gorana Pobric ◽  
Matthew A. Lambon Ralph ◽  
Roland Zahn

Studies of semantic dementia, imaging, and repetitive TMS have suggested that the bilateral anterior temporal lobes (ATLs) underpin a modality-invariant representational hub within the semantic system. Questions remain, however, regarding functional specialization across a variety of knowledge domains within the ATL region. We investigated direct evidence for the functional relevance of the superior ATL in processing social concepts. Using converging evidence from noninvasive brain stimulation and neuropsychology, we demonstrate graded differentiation of right and left superior anterior temporal areas in social cognition. Whereas the left superior ATL is necessary for processing both social and nonsocial abstract concepts, social conceptual processing predominates in the right superior ATL. This graded hemispheric specialization is mirrored in the patient results. Our data shed new light on the classic debate about hemispheric differences in semantic and social cognition. These results are considered in the context of models of semantic representation and the emerging data on connectivity for left and right ATL regions.


2020 ◽  
Vol 30 (6) ◽  
pp. 3838-3855 ◽  
Author(s):  
Steven M Frankland ◽  
Joshua D Greene

Abstract To understand a simple sentence such as “the woman chased the dog”, the human mind must dynamically organize the relevant concepts to represent who did what to whom. This structured recombination of concepts (woman, dog, chased) enables the representation of novel events, and is thus a central feature of intelligence. Here, we use functional magnetic resonance (fMRI) and encoding models to delineate the contributions of three brain regions to the representation of relational combinations. We identify a region of anterior-medial prefrontal cortex (amPFC) that shares representations of noun-verb conjunctions across sentences: for example, a combination of “woman” and “chased” to encode woman-as-chaser, distinct from woman-as-chasee. This PFC region differs from the left-mid superior temporal cortex (lmSTC) and hippocampus, two regions previously implicated in representing relations. lmSTC represents broad role combinations that are shared across verbs (e.g., woman-as-agent), rather than narrow roles, limited to specific actions (woman-as-chaser). By contrast, a hippocampal sub-region represents events sharing narrow conjunctions as dissimilar. The success of the hippocampal conjunctive encoding model is anti-correlated with generalization performance in amPFC on a trial-by-trial basis, consistent with a pattern separation mechanism. Thus, these three regions appear to play distinct, but complementary, roles in encoding compositional event structure.


2012 ◽  
Vol 1 (2) ◽  
Author(s):  
Swantje Zachau ◽  
Paavo H.T. Leppänen ◽  
Leena Ervast ◽  
Kaisu Heinänen ◽  
Kalervo Suominen ◽  
...  

AbstractLexical representation of natural signed language in interrelation to speech was explored by analyzing hearing signers’ and non-signers’ behavioral response patterns to a within- and across-language semantic decision task. Native hearing signers, non-native sign language interpreters and sign-naïve controls had to decide whether two lexical items (speech-speech or speech-sign) were antonymic or not. Aim of this study was to examine whether sign language and speech are interacting with each other on the semantic level. Response patterns indicate semantic effects on within-language conditions in all three groups, whereas clear semantically motivated responses to cross-language conditions were only apparent in the two signing groups, though with different functional distribution. Our data demonstrate how tightly signing and speech can be interconnected at the semantic level. This linkage is at least partly learned and connected with language usage.


Sign in / Sign up

Export Citation Format

Share Document