• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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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.

• Phonetics and Speech Sciences
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• v.8 no.1
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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.

• Korean Journal of Pharmacognosy
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• v.51 no.4
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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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• v.37 no.11
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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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• v.25 no.3
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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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• v.19 no.4
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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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• v.36 no.3
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• pp.751-763
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• 2016

In this article, we conducted a literature review about cognitive aging and social-psychological factors that influence cognitive function in old age. As getting older, cognitive function was mostly seen as declining, even though the effect of aging is differential across domains of cognitive ability. The negative view about cognitive aging might be reflecting social-psychological factors such as age stereotypes. Age stereotypes vary among different cultures, but appear to be negative in general. Negative age stereotypes are related to lower level of memory performances. Older adults who were experimentally presented with positive age stereotypes exhibited better memory performances than those with negative age stereotypes. Self-referent belief, appraisals of one's own cognitive abilities, could also affect actual performance in cognitive tasks. Older adults showed lower self-referent belief than younger adults, and it might explain memory decline in old age. Theoretical explanation and implication about the relationship between social-psychological factors and cognitive abilities were discussed.

• Korean Journal of Audiology
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• v.25 no.4
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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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• v.25 no.4
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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.

• Science of Emotion and Sensibility
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• v.14 no.3
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• pp.425-434
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• 2011

In the present study was to examine the influence of cold stress conditions on memory function in relation with 5-hydroxytryptamine(serotonin, 5-HT), trptophanhydroxylase(TPH) expression and cell proliferation in the hippocampus. For this study, male Sprague-Dawley rats weighing $250{\pm}10g$ (7 weeks in age) were used. The rats were randomly divided into three groups(n = 10 in each group): the $22^{\circ}C$-control group, the $4^{\circ}C$-3 days group, the $4^{\circ}C$-5 weeks group. The environmental temperature at $22^{\circ}C$ set as the normal conditions, $4^{\circ}C$ was as the cold stress conditions. The present results showed that cold stress conditions shorten latency, representing cold stress disturbed memory function. 5-HT and TPH expressions in the dorsal raphe were increased cold stress. Neurogenesis in the dentate gyrus was increased under cold conditions. The present study revealed that cold stress exerted deteriorative memory function. However, through increasing of 5-HT, TPH and BrdU expression under cold stress conditions did not show memory enhancing effect.