• 대한기계학회논문집A
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• 제26권7호
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• pp.1223-1231
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• 2002

Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate microstructures and mechanical properties. The analysis of SEM and EDS showed that the composites have shown good interface bonding. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of prestrain, and it showed that the yield stress at 363K was higher than that of the room temperature. Especially, the yield stress of this composite increases with increasing the amount of prestrain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. Microstructural observation has revealed that interfacial reactions occur between the matrix and fiber, creating two intermetallic layers.

• 말소리와 음성과학
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• 제8권1호
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• pp.63-69
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• 2016

The aims of the present study are two-fold: 1) to explore differences on speech perception between younger and older adults according to noise conditions; and 2) to investigate which cognitive domains are correlated with speech perception. Data were acquired from 15 younger adults and 15 older adults. Sentence recognition test was conducted in four noise conditions(i.e., in-quiet, +5 dB SNR, 0 dB SNR, -5 dB SNR). All participants completed auditory and cognitive assessment. Upon controlling for hearing thresholds, the older group revealed significantly poorer performance compared to the younger adults only under the high noise condition at -5 dB SNR. For older group, performance on Seoul Verbal Learning Test(immediate recall) was significantly correlated with speech perception performance, upon controlling for hearing thresholds. In older adults, working memory and verbal short-term memory are the best predictors of speech-in-noise perception. The current study suggests that consideration of cognitive function for older adults in speech perception assessment is necessary due to its adverse effect on speech perception under background noise.

• 생약학회지
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• 제51권4호
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• pp.310-316
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• 2020

Kyung-Ok-Go (KOK) is a traditional prescription used for debilitating natural aging and post-illness debilitation. KOK has been used in a variety of ways because it strengthens immunity, prevents illness, and helps recovery in case of illness. In particular, recent research has revealed that KOK helps improve memory and cognition. Therefore, in this study, we investigated whether KOK was effective in improving memory decline and depression-state observed during menopause. In the present study, we employed ovariectomized mouse as an animal model for measuring menopausal syndrome. The administration of KOK for 8 weeks, the object recognition memory and working memory were improved in novel object recognition test and Y-maze test. And in the forced swimming test, the immobility time were decreased. Additionally, the expression level of mature brain derived neurotropic factor (mBDNF) was increased by KOK administration in ovariectomized mouse hippocampus. These results suggested that KOK could improve cognitive decline and depression during menopausal period, and it might be come from enhancing expression level of mBDNF in hippocampus.

• Molecules and Cells
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• 제37권11호
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• pp.767-776
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• 2014

Alzheimer's disease (AD) is clinically characterized with progressive memory loss and cognitive decline. Synaptic dysfunction is an early pathological feature that occurs prior to neurodegeneration and memory dysfunction. Mounting evidence suggests that aggregation of amyloid-${\alpha}$ ($A{\alpha}$) and hyperphosphorylated tau leads to synaptic deficits and neurodegeneration, thereby to memory loss. Among the established genetic risk factors for AD, the ${\varepsilon}4$ allele of apolipoprotein E (APOE) is the strongest genetic risk factor. We and others previously demonstrated that apoE regulates $A{\alpha}$ aggregation and clearance in an isoform-dependent manner. While the effect of apoE on $A{\alpha}$ may explain how apoE isoforms differentially affect AD pathogenesis, there are also other underexplored pathogenic mechanisms. They include differential effects of apoE on cerebral energy metabolism, neuroinflammation, neurovascular function, neurogenesis, and synaptic plasticity. ApoE is a major carrier of cholesterols that are required for neuronal activity and injury repair in the brain. Although there are a few conflicting findings and the underlying mechanism is still unclear, several lines of studies demonstrated that apoE4 leads to synaptic deficits and impairment in long-term potentiation, memory and cognition. In this review, we summarize current understanding of apoE function in the brain, with a particular emphasis on its role in synaptic plasticity and the underlying cellular and molecular mechanisms, involving low-density lipoprotein receptor-related protein 1 (LRP1), syndecan, and LRP8/ApoER2.

• Biomolecules & Therapeutics
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• 제25권3호
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• pp.249-258
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• 2017

To examine the effect of biflorin, a component of Syzygium aromaticum, on memory deficit, we introduced a scopolamine-induced cognitive deficit mouse model. A single administration of biflorin increased latency time in the passive avoidance task, ameliorated alternation behavior in the Y-maze, and increased exploration time in the Morris water maze task, indicating the improvement of cognitive behaviors against cholinergic dysfunction. The biflorin-induced reverse of latency in the scopolamine-treated group was attenuated by MK-801, an NMDA receptor antagonist. Biflorin also enhanced cognitive function in a naïve mouse model. To understand the mechanism of biflorin for memory amelioration, we performed Western blot. Biflorin increased the activation of protein kinase C-${\zeta}$ and its downstream signaling molecules in the hippocampus. These results suggest that biflorin ameliorates drug-induced memory impairment by modulation of protein kinase C-${\zeta}$ signaling in mice, implying that biflorin could function as a possible therapeutic agent for the treatment of cognitive problems.

• Journal of Korean Biological Nursing Science
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• 제19권4호
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• pp.276-283
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• 2017

Purpose: The aim of this study was to identify the effects of environmental factors on depressive-like behavior and memory function during adolescence. We performed behavior tests in adolescent rats exposed to environmental enrichment, handling, and social deprivation for eight weeks. Methods: Wistar rats were randomly assigned to control, environmental enrichment, handling, and social deprivation groups at the age of four weeks. Results: In the forced swim test, the immobility time in the environmental enrichment group was decreased than that in the control group (p=.038), while the immobility time in the social deprivation group was increased than that in the control group (p=.035), the environmental enrichment group (p<.001), and the handling group (p=.001). In the Morris water maze test, the social deprivation group had an increased latency time than the control group (p=.013) and the environmental enrichment group (p=.001). In the passive avoidance test, the environmental enrichment group had an increased latency time than the control group (p=.005). However, the social deprivation group had reduced latency time than the socially housed groups (control: p=.030; environmental enrichment: p<.001; handling: p<.001). Conclusion: These findings suggest that environmental factors play an important role in emotion and memory function during adolescence.

• 한국노년학
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• 제36권3호
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• pp.751-763
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• 2016

본 연구에서는 인지노화와 그에 영향을 미치는 사회심리학적 요인에 대해 개관하였다. 노화로 인한 인지기능의 변화는 세부 기능별로 상이함에도 인지노화는 쇠퇴의 관점으로 주로 해석되고 있다. 인지노화에 대한 부정적인 시각은 노화 고정관념(age stereotype)과 같은 사회심리학적 요인이 반영된 결과로 볼 수 있다. 노화 고정관념은 문화권에 따른 차이는 있으나 보통 부정적인 측면이 강하게 나타나는데, 더 부정적인 고정관념을 보일수록 기억 수행이 저하되는 것으로 나타났다. 노화 고정관념을 실험적으로 활성화시키는 경우, 긍정적인 고정관념을 제시받은 노인이 부정적인 고정관념을 제시받은 노인에 비해 더 높은 기억 수행을 보였다. 자신의 인지기능에 대한 평가인 자기신념(self-referent belief)도 인지기능에 영향을 미치는 것으로 나타난다. 보통 노인의 자기신념이 청년의 자기신념보다 낮게 나타나고, 자기기억신념의 수준은 실제 기억 수행과 관련되는 것으로 나타난다. 이상의 사회심리학적 요인이 인지기능에 미치는 영향에 대한 이론적 설명과 시사점이 논의되었다.

• 대한청각학회지
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• 제25권4호
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• pp.178-188
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• 2021

Background and Objectives: The influence of musical aptitude on cognitive test performance in musicians is a long-debated research question. Evidence points to the low performance of nonmusicians in visual and auditory cognitive tasks (working memory and attention) compared with musicians. This cannot be generalized to all nonmusicians, as a sub-group in this population can have innate musical abilities even without any formal musical training. The present study aimed to study the effect of musical aptitude on the working memory and selective attention. Subjects and Methods: Three groups of 20 individuals each (a total of 60 participants), including trained-musicians, nonmusicians with good musical aptitude, and nonmusicians with low musical aptitude, participated in the present study. Cognitive-based visual (Flanker's selective attention test) and auditory (working memory tests: backward digit span and operation span) tests were administered. Results: MANOVA (followed by ANOVA) revealed a benefit of musicianship and musical aptitude on backward digit span and Flanker's reaction time (p<0.05). Discriminant function analyses showed that the groups could be effectively (accuracy, 80%) segregated based on the backward digit span and Flanker's selective attention test. Trained musicians and nonmusicians with good musical aptitude were distinguished as one cluster and nonmusicians with low musical aptitude formed another cluster, hinting the role of musical aptitude in working memory and selective attention. Conclusions: Nonmusicians with good musical aptitude can have enhanced working memory and selective attention skills like musicians. Hence, caution is required when these individuals are included as controls in cognitive-based visual and auditory experiments.

• Journal of Audiology & Otology
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• 제25권4호
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• pp.178-188
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• 2021

Background and Objectives: The influence of musical aptitude on cognitive test performance in musicians is a long-debated research question. Evidence points to the low performance of nonmusicians in visual and auditory cognitive tasks (working memory and attention) compared with musicians. This cannot be generalized to all nonmusicians, as a sub-group in this population can have innate musical abilities even without any formal musical training. The present study aimed to study the effect of musical aptitude on the working memory and selective attention. Subjects and Methods: Three groups of 20 individuals each (a total of 60 participants), including trained-musicians, nonmusicians with good musical aptitude, and nonmusicians with low musical aptitude, participated in the present study. Cognitive-based visual (Flanker's selective attention test) and auditory (working memory tests: backward digit span and operation span) tests were administered. Results: MANOVA (followed by ANOVA) revealed a benefit of musicianship and musical aptitude on backward digit span and Flanker's reaction time (p<0.05). Discriminant function analyses showed that the groups could be effectively (accuracy, 80%) segregated based on the backward digit span and Flanker's selective attention test. Trained musicians and nonmusicians with good musical aptitude were distinguished as one cluster and nonmusicians with low musical aptitude formed another cluster, hinting the role of musical aptitude in working memory and selective attention. Conclusions: Nonmusicians with good musical aptitude can have enhanced working memory and selective attention skills like musicians. Hence, caution is required when these individuals are included as controls in cognitive-based visual and auditory experiments.

• 감성과학
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• 제14권3호
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• pp.425-434
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• 2011

본 연구의 목표는 일반적으로 사람들이 일상에서의 추위 노출 시간을 고려하여 단기간 추위노출과 지속적인 장기간의 추위 노출이 인지기능과 뇌의 신경세포생성과 신경전달물질에 미치는 영향을 규명하고자 하였다. 실험 방법으로 인지행동검사(Behavior test)와 면역조직화학법(Immunohistochemistry Method)을 실시하였다. 본 연구에서는 7주령(평균체중 $250{\pm}10g$) Sprague-Dawley 계열의 수컷 흰쥐(n=40)를 사용하여, 무선배치 방식으로 상온 대조군(n=10), 저온 3일군(n=10), 저온 5주군(n=10)으로 분류 하였다. $22^{\circ}C$(상대습도 40%)의 온도는 상온으로 설정 하였고, $4^{\circ}C$(상대습도 40%)는 추위 스트레스 환경으로 설정 하였다. 수동회피실험의 결과에 의하면, 추위 스트레스는 기억력의 감소를 가져왔다. 그러나 추위 스트레스에 의한 기억력 감소의 보상작용으로 신경전달 물질인 5-HT와 TPH의 증가가 나타나는 것을 면역조직화학법을 통해 해부시경학적으로 확인할 수 있었다. 그러나 보상작용에 의한 새로운 신경세포생성 증가가 기억력을 정상상태로 회복시키지는 못하였다.