The Experts below are selected from a list of 30825 Experts worldwide ranked by ideXlab platform
John X. Zhang - One of the best experts on this subject based on the ideXlab platform.
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the anterior left inferior Frontal Gyrus contributes to semantic unification
NeuroImage, 2012Co-Authors: Peter Hagoort, John X. Zhang, Hsuan-chih Chen, Gengyi Feng, Marcel C M Bastiaansen, Suiping WangAbstract:Semantic unification, the process by which small blocks of semantic information are combined into a coherent utterance, has been studied with various types of tasks. However, whether the brain activations reported in these studies are attributed to semantic unification per se or to other task-induced concomitant processes still remains unclear. The neural basis for semantic unification in sentence comprehension was examined using event-related potentials (ERP) and functional Magnetic Resonance Imaging (fMRI). The semantic unification load was manipulated by varying the goodness of fit between a critical word and its preceding context (in high cloze, low cloze and violation sentences). The sentences were presented in a serial visual presentation mode. The participants were asked to perform one of three tasks: semantic congruency judgment (SEM), silent reading for comprehension (READ), or font size judgment (FONT), in separate sessions. The ERP results showed a similar N400 amplitude modulation by the semantic unification load across all of the three tasks. The brain activations associated with the semantic unification load were found in the anterior left inferior Frontal Gyrus (aLIFG) in the FONT task and in a widespread set of regions in the other two tasks. These results suggest that the aLIFG activation reflects a semantic unification, which is different from other brain activations that may reflect task-specific strategic processing.
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The role of left inferior Frontal Gyrus in explicit and implicit semantic processing
Brain Research, 2011Co-Authors: Jian Huang, John X. Zhang, Mingxiang Wu, Hsuan-chih Chen, Suiping WangAbstract:Abstract Using event-related functional MRI, we examined the involvement of the left inferior Frontal Gyrus (LIFG) in explicit and implicit semantic processing of Chinese sentences. During scanning, Chinese readers read individually presented normal sentences with a contextually expected or unexpected target noun and were asked to perform an explicit or implicit semantic task (semantic or syntactic violation judgment). The conjunction analysis of the two tasks revealed LIFG as the critical brain region for semantic integration. Further, a cross-task comparison showed more extensive activations for the expectancy effect in the explicit task than in the implicit task in regions including bilateral anterior cingulate cortex/dorsolateral preFrontal cortex, left middle temporal Gyrus, and right inferior Frontal Gyrus. These results indicate that LIFG is responsible for the integration process per se and that other brain regions observed in previous studies using explicit semantic tasks may be due to task-induced generic processes (e.g., cognitive control).
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involvement of left inferior Frontal Gyrus in sentence level semantic integration
NeuroImage, 2009Co-Authors: John X. Zhang, Jian Huang, Suiping Wang, Zhuangwei Xiao, Hsuan-chih ChenAbstract:Abstract Using event-related functional MRI, we examined the involvement of the left inferior Frontal Gyrus (LIFG) in semantic integration in reading Chinese sentences. During scanning, Chinese readers read individually presented sentences and judged whether or not a sentence was semantically acceptable. Behaviorally, those sentences with a small degree of semantic violation were found to be more difficult to reject relative to sentences with a large degree of semantic violation, indicating that more semantic integration occurred in the former than in the latter condition. Direct contrast revealed significantly greater brain activity in the LIFG for sentences with a small violation, relative to those with a large violation, but no differences in any anterior temporal cortical areas between the two types of anomalous sentences. The results are in line with the idea that the LIFG plays a critical role in integrating individual word meanings to coherent sentence-level messages, but not with the idea that semantic integration depends on anterior temporal cortex in language comprehension.
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Involvement of the left inferior Frontal Gyrus in predictive inference making.
International Journal of Psychophysiology, 2008Co-Authors: Lei Mo, Shin Yi Fang, John X. ZhangAbstract:Although predictive inference in reading has been extensively investigated with behavioral paradigms, little is known about its neural substrates. Manipulating the likelihood that a particular event can be predicted from the content of a preceding three-sentence story, the present functional MRI study showed that the left inferior Frontal Gyrus (LIFG) and the right lingual Gyrus were involved in predictive inference generation. It is suggested that the LIFG was responsible for the construction of predictive inference and the right lingual Gyrus for integrating the constructed inference into a coherent text representation. Combined with previous research, the results provide brain imaging evidence consistent with predictions from the Schmalhofer et al. model (Discourse Processes, 33, 105-13, 2002) which intends to unify predictive inference and bridging inference in a single theoretical framework.
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differential activity in left inferior Frontal Gyrus for pseudowords and real words an event related fmri study on auditory lexical decision
Human Brain Mapping, 2005Co-Authors: Zhuangwei Xiao, John X. Zhang, Xiaoyi Wang, Renhua Wu, Xiaoping Hu, Xuchu WengAbstract:After Newman and Twieg ([2001]: Hum Brain Mapp 14:39-47) and others, we used a fast event-related functional magnetic resonance imaging (fMRI) design and contrasted the lexical processing of pseudowords and real words. Participants carried out an auditory lexical decision task on a list of randomly intermixed real and pseudo Chinese two-character (or two-syllable) words. The pseudowords were constructed by recombining constituent characters of the real words to control for sublexical code properties. Processing of pseudowords and real words activated a highly comparable network of brain regions, including bilateral inferior Frontal Gyrus, superior, middle temporal Gyrus, calcarine and lingual Gyrus, and left supramarginal Gyrus. Mirroring a behavioral lexical effect, left inferior Frontal Gyrus (IFG) was significantly more activated for pseudowords than for real words. This result disconfirms a popular view that this area plays a role in grapheme-to-phoneme conversion, as such a conversion process was unnecessary in our task with auditory stimulus presentation. An alternative view was supported that attributes increased activity in left IFG for pseudowords to general processes in decision making, specifically in making positive versus negative responses. Activation in left supramarginal Gyrus was of a much larger volume for real words than for pseudowords, suggesting a role of this region in the representation of phonological or semantic information for two-character Chinese words at the lexical level.
Hideyuki Kikyo - One of the best experts on this subject based on the ideXlab platform.
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memory of music roles of right hippocampus and left inferior Frontal Gyrus
NeuroImage, 2008Co-Authors: Takamitsu Watanabe, Sho Yagishita, Hideyuki KikyoAbstract:Abstract We investigated neural correlates of retrieval success for music memory using event-related functional magnetic resonance imaging. To minimize the interference from MRI scan noise, we used sparse temporal sampling technique. Newly composed music materials were employed as stimuli, which enabled us to detect regions in absence of effects of experience with the music stimuli in this study. Whole brain analyses demonstrated significant retrieval success activities in the right hippocampus, bilateral lateral temporal regions, left inferior Frontal Gyrus and left precuneus. Anatomically defined region-of-interests analyses showed that the activity of the right hippocampus was stronger than that of the left, while the activities of the inferior Frontal gyri showed the reverse pattern. Furthermore, performance-based analyses demonstrated that the retrieval success activity of the right hippocampus was positively correlated with the corrected recognition rate, suggesting that the right hippocampus contributes to the accuracy of music retrieval outcome.
Lorraine K. Tyler - One of the best experts on this subject based on the ideXlab platform.
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Dissociating Linguistic and Task-related Activity in the Left Inferior Frontal Gyrus
Journal of Cognitive Neuroscience, 2011Co-Authors: Paul Wright, Billi Randall, William D. Marslen-wilson, Lorraine K. TylerAbstract:The left inferior Frontal Gyrus (LIFG) has long been claimed to play a key role in language function. However, there is considerable controversy as to whether regions within LIFG have specific linguistic or domain-general functions. Using fMRI, we contrasted linguistic and task-related effects by presenting simple and morphologically complex words while subjects performed a lexical decision (LD) task or passively listened (PL) without making an overt response. LIFG Brodmann's area 47 showed greater activation in LD than PL, whereas LIFG Brodmann's area 44 showed greater activation to complex compared with simple words in both tasks. These results dissociate task-driven and obligatory language processing in LIFG and suggest that PL is the paradigm of choice for probing the core aspects of the neural language system.
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selecting among competing alternatives selection and retrieval in the left inferior Frontal Gyrus
Cerebral Cortex, 2005Co-Authors: Helen E Moss, S Abdallah, Paul C Fletcher, Peter Bright, Lea K Pilgrim, K Acres, Lorraine K. TylerAbstract:It has been widely argued that the left inferior Frontal Gyrus (LIFG) is involved in the control of retrieval of information from long-term memory. Recent claims that the LIFG is involved in selecting among semantic alternatives have been challenged on the grounds that the manipulation of selection demands may have been confounded with controlled retrieval. The current study used an event-related functional magnetic resonance paradigm to re-examine the possibility that LIFG activation is involved in selection processes. In order to minimize potential confounding effects of controlled retrieval, we used an automatic retrieval task (picture naming) and held retrieval demands constant, while varying selection demands by way of competitor priming from earlier semantically related trials. We found significant activation in LIFG as a function of increased selection demands; activation centred on two peaks, one in anterior LIFG and a second more superior and posterior region. These data support the view that LIFG plays a role in selection among semantic information, even in the absence of controlled retrieval processes.
Bruce Fischl - One of the best experts on this subject based on the ideXlab platform.
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gray matter volume reduction in rostral middle Frontal Gyrus in patients with chronic schizophrenia
Schizophrenia Research, 2010Co-Authors: Zora Kikinis, James H Fallon, Margaret A Niznikiewicz, Paul G Nestor, Charlie A Davidson, L H Bobrow, Paula E Pelavin, Bruce FischlAbstract:Abstract The dorsolateral preFrontal cortex (DLPFC) is a brain region that has figured prominently in studies of schizophrenia and working memory, yet the exact neuroanatomical localization of this brain region remains to be defined. DLPFC primarily involves the superior Frontal Gyrus and middle Frontal Gyrus (MFG). The latter, however is not a single neuroanatomical entity but instead is comprised of rostral (anterior, middle, and posterior) and caudal regions. In this study we used structural MRI to develop a method for parcellating MFG into its component parts. We focused on this region of DLPFC because it includes BA46, a region involved in working memory. We evaluated volume differences in MFG in 20 patients with chronic schizophrenia and 20 healthy controls. Mid-rostral MFG (MR-MFG) was delineated within the rostral MFG using anterior and posterior neuroanatomical landmarks derived from cytoarchitectonic definitions of BA46. Gray matter volumes of MR-MFG were then compared between groups, and a significant reduction in gray matter volume was observed ( p
James M Kilner - One of the best experts on this subject based on the ideXlab platform.
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dissociable roles of human inferior Frontal Gyrus during action execution and observation
NeuroImage, 2012Co-Authors: Clare Press, Nikolaus Weiskopf, James M KilnerAbstract:There has been recent controversy about whether activation in the human inferior Frontal Gyrus (IFG) and Brodmann Area (BA) 6 when observing actions indicates operation of mirror neurons. Recent functional magnetic resonance imaging (fMRI) data have demonstrated repetition suppression (RS) effects in posterior IFG which are consistent with the presence of mirror neurons in humans. Here we investigated whether there were similar RS effects elsewhere in the IFG and BA6, or whether, instead, activation in other locations may signal operation of alternative mechanisms. Replicating previous findings, we found RS effects in posterior IFG consistent with the operation of mirror neurons. However, these effects were not found in other locations in IFG and BA6. Additionally, activation patterns in anterior regions of IFG suggested dissociable operations when observing and executing actions. Therefore, caution should be exercised when claiming that activations in many locations during action observation indicate the operation of mirror neurons. Activation may instead reflect alternative mechanisms, such as encoding of the semantic features of actions.
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evidence of mirror neurons in human inferior Frontal Gyrus
The Journal of Neuroscience, 2009Co-Authors: James M Kilner, Alice Neal, Nikolaus Weiskopf, Karl J Friston, C D FrithAbstract:There is much current debate about the existence of mirror neurons in humans. To identify mirror neurons in the inferior Frontal Gyrus (IFG) of humans, we used a repetition suppression paradigm while measuring neural activity with functional magnetic resonance imaging. Subjects either executed or observed a series of actions. Here we show that in the IFG, responses were suppressed both when an executed action was followed by the same rather than a different observed action and when an observed action was followed by the same rather than a different executed action. This pattern of responses is consistent with that predicted by mirror neurons and is evidence of mirror neurons in the human IFG.
