Publications by authors named "Hyeon-Ae Jeon"

15 Publications

  • Page 1 of 1

Resting-State Functional Connectivity in Mathematical Expertise.

Brain Sci 2021 Mar 28;11(4). Epub 2021 Mar 28.

Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea.

To what extent are different levels of expertise reflected in the functional connectivity of the brain? We addressed this question by using resting-state functional magnetic resonance imaging (fMRI) in mathematicians versus non-mathematicians. To this end, we investigated how the two groups of participants differ in the correlation of their spontaneous blood oxygen level-dependent fluctuations across the whole brain regions during resting state. Moreover, by using the classification algorithm in machine learning, we investigated whether the resting-state fMRI networks between mathematicians and non-mathematicians were distinguished depending on features of functional connectivity. We showed diverging involvement of the frontal-thalamic-temporal connections for mathematicians and the medial-frontal areas to precuneus and the lateral orbital gyrus to thalamus connections for non-mathematicians. Moreover, mathematicians who had higher scores in mathematical knowledge showed a weaker connection strength between the left and right caudate nucleus, demonstrating the connections' characteristics related to mathematical expertise. Separate functional networks between the two groups were validated with a maximum classification accuracy of 91.19% using the distinct resting-state fMRI-based functional connectivity features. We suggest the advantageous role of preconfigured resting-state functional connectivity, as well as the neural efficiency for experts' successful performance.
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http://dx.doi.org/10.3390/brainsci11040430DOI Listing
March 2021

Potential and efficiency of statistical learning closely intertwined with individuals' executive functions: a mathematical modeling study.

Sci Rep 2020 11 2;10(1):18843. Epub 2020 Nov 2.

Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea.

Statistical learning (SL) is essential in enabling humans to extract probabilistic regularities from the world. The ability to accomplish ultimate learning performance with training (i.e., the potential of learning) has been known to be dissociated with performance improvement per amount of learning time (i.e., the efficiency of learning). Here, we quantified the potential and efficiency of SL separately through mathematical modeling and scrutinized how they were affected by various executive functions. Our results showed that a high potential of SL was associated with poor inhibition and good visuo-spatial working memory, whereas high efficiency of SL was closely related to good inhibition and good set-shifting. We unveiled the distinct characteristics of SL in relation to potential and efficiency and their interaction with executive functions.
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http://dx.doi.org/10.1038/s41598-020-75157-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7606401PMC
November 2020

Syntactic Comprehension of Relative Clauses and Center Embedding Using Pseudowords.

Brain Sci 2020 Mar 31;10(4). Epub 2020 Mar 31.

Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea.

Relative clause (RC) formation and center embedding (CE) are two primary syntactic operations fundamental for creating and understanding complex sentences. Ample evidence from previous cross-linguistic studies has revealed several similarities and differences between RC and CE. However, it is not easy to investigate the effect of pure syntactic constraints for RC and CE without the interference of semantic and pragmatic interactions. Here, we show how readers process CE and RC using a self-paced reading task in Korean. More interestingly, we adopted a novel self-paced pseudoword reading task to exploit syntactic operations of the RC and CE, eliminating the semantic and pragmatic interference in sentence comprehension. Our results showed that the main effects of RC and CE conform to previous studies. Furthermore, we found a facilitation effect of sentence comprehension when we combined an RC and CE in a complex sentence. Our study provides a valuable insight into how the purely syntactic processing of RC and CE assists comprehension of complex sentences.
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http://dx.doi.org/10.3390/brainsci10040202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7226570PMC
March 2020

Mathematical expertise modulates the architecture of dorsal and cortico-thalamic white matter tracts.

Sci Rep 2019 05 2;9(1):6825. Epub 2019 May 2.

Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany.

To what extent are levels of cognitive expertise reflected in differential structural connectivity of the brain? We addressed this question by analyzing the white matter brain structure of experts (mathematicians) versus non-experts (non-mathematicians) using probabilistic tractography. Having mathematicians and non-mathematicians as participant groups enabled us to directly compare profiles of structural connectivity arising from individual levels of expertise in mathematics. Tracking from functional seed regions activated during the processing of complex arithmetic formulas revealed an involvement of various fiber bundles such the inferior fronto-occipital fascicle, arcuate fasciculus/superior longitudinal fasciculus (AF/SLF), cross-hemispheric connections of frontal lobe areas through the corpus callosum and cortico-subcortical connectivity via the bilateral thalamic radiation. With the aim of investigating expertise-dependent structural connectivity, the streamline density was correlated with the level of expertise, defined by automaticity of processing complex mathematics. The results showed that structural integrity of the AF/SLF was higher in individuals with higher automaticity, while stronger cortico-thalamic connectivity was associated with lower levels of automaticity. Therefore, we suggest that expertise in the domain of mathematics is reflected in plastic changes of the brain's white matter structure, possibly reflecting a general principle of cognitive expertise.
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http://dx.doi.org/10.1038/s41598-019-43400-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497695PMC
May 2019

What Does "Being an Expert" Mean to the Brain? Functional Specificity and Connectivity in Expertise.

Cereb Cortex 2017 12;27(12):5603-5615

Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103Leipzig, Germany.

To what extent is varying cognitive expertise reflected in the brain's functional specificity and connectivity? We addressed this question by examining expertise in mathematics based on the fact that mathematical skills are one of the most critical cognitive abilities known to be a good predictor of academic achievement. We investigated processing of hierarchical structures, which is a fundamental process for building complex cognitive architecture. Experts and nonexperts in mathematics participated in processing hierarchical structures using algebraic expressions. Results showed that a modulating effect depending on expertise was observed specifically in nonexperts in the left inferior frontal gyrus around pars triangularis and frontal sulcus, the left intraparietal sulcus, and the right inferior parietal lobule. This expertise-dependent pattern of activation led to a crucial dissociation within the left prefrontal cortex. More interestingly, task-related functional networks were also modulated differently in the frontoparietal network for relatively good performance and in the frontostriatal network for poor performance. The present study indicates that a high level of expertise is evident in a small number of specific brain regions, whereas a low level of expertise is reflected by broadly distributed brain areas, along with divergent functional connectivity between experts and nonexperts.
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http://dx.doi.org/10.1093/cercor/bhw329DOI Listing
December 2017

Degree of automaticity and the prefrontal cortex.

Trends Cogn Sci 2015 May 2;19(5):244-50. Epub 2015 Apr 2.

Max Planck Institute for Human Cognitive and Brain Sciences, Department of Neuropsychology, Leipzig, Germany.

The dorsolateral prefrontal cortex (PFC), with more anterior areas [Brodmann area (BA) 45, 47, and 10], has been known to be activated as cognitive hierarchy increases. However, this does not hold for highly automatic processes such as first language (L1), where the posterior region (BA 44) is known as the key area for the processing of complex linguistic hierarchy. Discussing this disparity, we propose that the degree of automaticity (DoA) is a crucial factor for the framework of functional mapping in the PFC: the posterior-to-anterior gradient system for more controlled processes and the posterior-confined system for automatic processes. We support this view with previous findings and provide a new perspective on the functional organization of the PFC.
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http://dx.doi.org/10.1016/j.tics.2015.03.003DOI Listing
May 2015

Hierarchical processing in the prefrontal cortex in a variety of cognitive domains.

Authors:
Hyeon-Ae Jeon

Front Syst Neurosci 2014 25;8:223. Epub 2014 Nov 25.

Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany.

This review scrutinizes several findings on human hierarchical processing within the prefrontal cortex (PFC) in diverse cognitive domains. Converging evidence from previous studies has shown that the PFC, specifically, BA44, may function as the essential region for hierarchical processing across the domains. In language fMRI studies, BA 44 was significantly activated for the hierarchical processing of center-embedded sentences and this pattern of activations was also observed in artificial grammar. The same pattern was observed in the visuo-spatial domain where BA44 was actively involved in the processing of hierarchy for the visual symbol. Musical syntax, which is the rule-based arrangement of musical sets, has also been construed as hierarchical processing as in the language domain such that the activation in BA44 was observed in a chord sequence paradigm. P600 ERP was also engendered during the processing of musical hierarchy. Along with a longstanding idea that a human's number faculty is developed as a "by-product of language faculty", BA44 was closely involved in hierarchical processing in mental arithmetic. This review extended its discussion of hierarchical "processing" to hierarchical "behavior", that is, human action which has been referred to as being hierarchically composed. Several lesion and TMS studies supported the involvement of BA44 for hierarchical processing in the action domain. Lastly, the hierarchical organization of cognitive controls was discussed within the PFC, forming a cascade of top-down hierarchical processes operating along a posterior-to-anterior axis of the lateral PFC including BA44 within the network. It is proposed that PFC is actively involved in different forms of hierarchical processing and specifically BA44 may play an integral role in the process. Taking levels of proficiency and subcortical areas into consideration may provide further insight into the functional role of BA44 for hierarchical processing.
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http://dx.doi.org/10.3389/fnsys.2014.00223DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4243503PMC
December 2014

Functional network mirrored in the prefrontal cortex, caudate nucleus, and thalamus: high-resolution functional imaging and structural connectivity.

J Neurosci 2014 Jul;34(28):9202-12

Max Planck Institute for Human Cognitive and Brain Sciences, Department of Neuropsychology, Leipzig, 04103, Leipzig, Germany.

Despite myriads of studies on a parallel organization of cortico-striatal-thalamo-cortical loops, direct evidence of this has been lacking for the healthy human brain. Here, we scrutinize the functional specificity of the cortico-subcortical loops depending on varying levels of cognitive hierarchy as well as their structural connectivity with high-resolution fMRI and diffusion-weighted MRI (dMRI) at 7 tesla. Three levels of cognitive hierarchy were implemented in two domains: second language and nonlanguage. In fMRI, for the higher level, activations were found in the ventroanterior portion of the prefrontal cortex (PFC), the head of the caudate nucleus (CN), and the ventral anterior nucleus (VA) in the thalamus. Conversely, for the lower level, activations were located in the posterior region of the PFC, the body of the CN, and the medial dorsal nucleus (MD) in the thalamus. This gradient pattern of activations was furthermore shown to be tenable by the parallel connectivity in dMRI tractography connecting the anterior regions of the PFC with the head of the CN and the VA in the thalamus, whereas the posterior activations of the PFC were linked to the body of the CN and the MD in the thalamus. This is the first human in vivo study combining fMRI and dMRI showing that the functional specificity is mirrored within the cortico-subcortical loop substantiated by parallel networks.
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http://dx.doi.org/10.1523/JNEUROSCI.0228-14.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6608361PMC
July 2014

Two principles of organization in the prefrontal cortex are cognitive hierarchy and degree of automaticity.

Nat Commun 2013 ;4:2041

Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany.

The lateral prefrontal cortex is known to be organized by cognitive hierarchies following a posterior-to-anterior gradient. Here we test whether this model applies across different cognitive domains by varying levels of cognitive hierarchy in first language, second language and non-language domains. These domains vary in their degree of automaticity with first language being the most automatic. For second language/non-language a clear gradient pattern of activation depending on the level of hierarchy is observed in the prefrontal cortex with the highest level of hierarchy recruiting its most anterior region, whereas for first language the highest level of hierarchy recruits its most posterior region. Moreover, second language/non-language and first language differ in the structural connectivity of their underlying networks. The current data strongly suggest that functional segregation of the prefrontal cortex is determined by cognitive hierarchy and the degree of automaticity.
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http://dx.doi.org/10.1038/ncomms3041DOI Listing
December 2013

Effect of lexical proficiency on reading strategies used for shallow and deep orthographies.

Authors:
Hyeon-Ae Jeon

Neuroreport 2012 Dec;23(17):979-83

Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.

The aim of the present study was to explore how different levels of proficiency in deep orthography (DO) influence the reading strategies used for sentences containing both shallow orthographies and DO, and to examine the neural correlates involved. High-proficiency participants, who depend on rapid and direct semantic retrieval by the lexical route, activated the anterior cingulate cortex, middle frontal, and fusiform gyri. Low-proficiency participants, who rely on the sublexical route, activated inferior parietal lobule and inferior frontal gyrus. These findings suggest that level of proficiency in DO modulates the selection of specific reading strategies, and that the neural pathways underlying these strategies are separately laid out in the cortical areas.
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http://dx.doi.org/10.1097/WNR.0b013e32835a19aeDOI Listing
December 2012

Increased basal forebrain metabolism in mild cognitive impairment: an evidence for brain reserve in incipient dementia.

J Alzheimers Dis 2012 ;32(4):927-38

Department of Neurology, Seoul National University Hospital, Seoul, Republic of Korea.

Cholinergic dysfunction is well known to significantly contribute to the cognitive decline in Alzheimer's disease (AD). However, it has not been clarified whether the cholinergic dysfunction is a primary event or a retrograde event secondary to neuronal loss of the cholinergic targets. Analysis of the in vivo neuronal activity of the basal forebrain in the early stages of AD could yield more information about this issue. In the present study, uptake of [18F]-fluorodeoxyglucose (FDG) in the basal forebrain was measured in 13 patients with mild cognitive impairment (MCI), 20 with early AD, and 14 healthy subjects using high-resolution research tomograph-PET. The FDG uptake was compared among the groups and correlated with the Mini Mental Status Examination (MMSE) score. The MCI patients showed significantly higher FDG uptake in the basal forebrain than the healthy subjects and the AD patients, and those did not developed dementia after 2 years showed even higher uptake than those developed dementia. The basal forebrain metabolism showed an inverted-U relationship with MMSE score in highly educated subjects, and cross-voxel analysis over the whole brain in MCI patients revealed a significant correlation in uptake between the basal forebrain and the fronto-temporal cortices. These findings indicate that in MCI patients, neuronal activity in the basal forebrain is initially increased over that in normal aging and then decreased only with further cognitive decline. The increase is consistent with a secondary compensation against neurodegeneration at target areas, and may provide brain reserve against functional impairments at incipient stages of dementia.
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http://dx.doi.org/10.3233/JAD-2012-120133DOI Listing
August 2013

Dual routes for verbal repetition: articulation-based and acoustic-phonetic codes for pseudoword and word repetition, respectively.

Brain Lang 2012 Jul 24;122(1):1-10. Epub 2012 May 24.

Interdisciplinary Program in Cognitive Science, Seoul National University, Republic of Korea.

Speech production is inextricably linked to speech perception, yet they are usually investigated in isolation. In this study, we employed a verbal-repetition task to identify the neural substrates of speech processing with two ends active simultaneously using functional MRI. Subjects verbally repeated auditory stimuli containing an ambiguous vowel sound that could be perceived as either a word or a pseudoword depending on the interpretation of the vowel. We found verbal repetition commonly activated the audition-articulation interface bilaterally at Sylvian fissures and superior temporal sulci. Contrasting word-versus-pseudoword trials revealed neural activities unique to word repetition in the left posterior middle temporal areas and activities unique to pseudoword repetition in the left inferior frontal gyrus. These findings imply that the tasks are carried out using different speech codes: an articulation-based code of pseudowords and an acoustic-phonetic code of words. It also supports the dual-stream model and imitative learning of vocabulary.
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http://dx.doi.org/10.1016/j.bandl.2012.04.011DOI Listing
July 2012

Neural substrates of semantic relationships: common and distinct left-frontal activities for generation of synonyms vs. antonyms.

Neuroimage 2009 Nov 25;48(2):449-57. Epub 2009 Jun 25.

Neuroscience Research Institute, Gachon University of Medicine and Science, 1198 Kuwol-dong, Namdong-gu, Incheon 405-760, Republic of Korea.

Synonymous and antonymous relationships among words may reflect the organization and/or processing in the mental lexicon and its implementation in the brain. In this study, functional magnetic resonance imaging (fMRI) is employed to compare brain activities during generation of synonyms (SYN) and antonyms (ANT) prompted by the same words. Both SYN and ANT, when compared with reading nonwords (NW), activated a region in the left middle frontal gyrus (BA 46). Neighboring this region, there was a dissociation observed in that the ANT activation extended more anteriorly and laterally to the SYN activation. The activations in the left middle frontal gyrus may be related to mental processes that are shared in the SYN and ANT generations, such as engaging semantically related parts of mental lexicon for the word search, whereas the distinct activations unique for either SYN or ANT generation may reflect the additional component of antonym retrieval, namely, reversing the polarity of semantic relationship in one crucial dimension. These findings suggest that specific components in the semantic processing, such as the polarity reversal for antonym generation and the similarity assessment for synonyms, are separately and systematically laid out in the left-frontal cortex.
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http://dx.doi.org/10.1016/j.neuroimage.2009.06.049DOI Listing
November 2009

Diagnostic utility of sound naming in early Alzheimer's disease.

J Int Neuropsychol Soc 2009 Mar 10;15(2):231-8. Epub 2009 Feb 10.

Seoul National University, Seoul, Korea.

While it is well known that picture naming (PN) is impaired in Alzheimer's disease (AD), sound naming (SN) has not been thoroughly investigated. We postulated that SN might be impaired more severely and earlier than PN, given the early involvement of the temporal cortex by AD-related pathology. SN and PN were assessed in 21 normal participants, 40 patients with mild cognitive impairment (MCI), and 27 patients in early stages of AD. Our results showed that SN accuracy and latency were more sensitive to advancing pathology in AD than PN accuracy and latency. SN was more useful and specific in distinguishing MCI patients from normal participants and therefore in potentially identifying the subset of MCI patients who already have impairment in more than one cognitive domain and may actually have incipient AD. These findings indicate a potential diagnostic utility of SN for early detection of the disease. Furthermore, even though most AD patients demonstrated more or less comparable impairment in both tasks, some were disproportionately impaired on SN and others were differentially impaired on PN. Future studies may be able to show that these discrepant groups correspond to patients with right and left hemisphere predominant AD, respectively.
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http://dx.doi.org/10.1017/S135561770909033XDOI Listing
March 2009

Neuroimaging features in a case of developmental central auditory processing disorder.

J Neurol Sci 2009 Feb 6;277(1-2):176-80. Epub 2008 Dec 6.

Department of Neurology, National Police Hospital, 58 Karak-Bon-Dong, Songpa-Gu, Seoul, 138-708, Republic of Korea.

We describe a case of developmental central auditory processing disorder (CAPD) that was diagnosed with a multidisciplinary approach including structural and functional neuroimaging. A patient with developmental CAPD was investigated using diagnostic tools of MRI and (18)F-FDG HRRT-PET as well as neuropsychology and electrophysiology. Besides impaired auditory processing, our patient also showed some impediments in supramodal, cognitive and linguistic processes. His MRI showed selective atrophy in the bilateral auditory cortices, and the PET images showed hypometabolism in the bilateral auditory cortices and the precuneus. Such a multidisciplinary diagnostic approach that includes neuroimaging methods will be helpful in differentiating developmental CAPD from other developmental cognitive disorders.
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http://dx.doi.org/10.1016/j.jns.2008.10.020DOI Listing
February 2009