• Sleep Medicine and Psychophysiology
• /
• v.8 no.2
• /
• pp.121-128
• /
• 2001

Objectives: In narcoleptic patients diagnosed with ICSD (international classification of sleep disorders, 1990) criteria, nocturnal polysomnography, and MSLT (multiple sleep latency test), we tried to find characteristic features of quantitative electroencephalography (QEEG) in a wakeful state. Methods: We compared eight drug-free narcoleptic patients with sex- and age-matched normal controls, using computerized electroencephalographic mapping technique and spectral analysis. Absolute power, relative power, interhemispheric asymmetry, interhemispheric and intrahemispheric coherence, and mean frequency in each frequency band (delta, theta, alpha and beta) were measured and analyzed. Results: Compared with normal controls, narcoleptic patients showed decrease in monopolar interhemispheric coherence of alpha frequency bands in occipital ($O_1/O_2$), parietal ($P_3/P_4$), and temporal ($T_5/T_6$) areas and beta frequency band in the occipital ($O_1/O_2$) area. Monopolar intrahemispheric coherences of alpha frequency bands in left hemispheric areas ($T_3/T_5$, $C_3/P_3$ & $F_3/O_1$) decreased. Decrease of monopolar interhemispheric asymmetry of delta frequency band in the occipital ($O_1/O_2$) area was also noted. The monopolar absolute powers of beta frequency bands decreased in occipital ($O_2,\;O_z$) areas. Conclusion: Decreases in coherences of narcoleptic patients compared with normal controls may indicate fewer posterior neocortical interhemispheric neuronal connections, and fewer left intrahemispheric neuronal connections than normal controls in a wakeful state. Therefore, we suggest that abnormal neurophysiological sites of narcolepsy may involve complex areas such as neocortex and subcortex as well as the brainstem.

• Korean Journal of Cognitive Science
• /
• v.26 no.4
• /
• pp.393-433
• /
• 2015

Creativity refers to the ability to generate novel and useful ideas. Understanding the mechanism of creativity and its enhancement is important in order to solve major problems of the modern society and to improve the wellness of mankind. Creativity is a highly heterogeneous and complex ability which should not be conceptualized as a single entity. Thus, the current literature on creativity is based on a component process approach to creativity. The present study introduces cognitive neuroscience research studying the mechanism of divergent thinking, insight, relational thinking and artistic creativity which are the major components of creativity. Based on an expansive review, the early hypothesis of hemispheric asymmetry emphasizing the importance of the right as opposed to the left hemisphere is not supported by scientific evidence. In addition, there is no consensus or consistency on which specific brain region is related to a certain component of creativity. In fact, there is a mixture of studies reporting involvement of various brain regions across all four lobes of the brain. This inconsistency in the literature most likely reflects heterogeneity of the component processes of creativity and sensitivity of the neural response to differences across tasks and cognitive strategy. The present study introduces examples of representative studies reporting seminal findings on the neural basis and the enhancement of creativity based on innovative methodology. In addition, we discuss limitations of the current cognitive neuroscience approach to creativity and present directions for future research.

• Annual Conference on Human and Language Technology
• /
• 1999.10e
• /
• pp.359-367
• /
• 1999

형태소를 공유하고 있는 어휘가 심성 어휘집(mental lexicon)에 어떻게 저장되어 있고 어떻게 어휘 접근되는지에 관하여 여러 설명이 제기되었다 첫 번째 가설은 형태소 공유 어휘는 심성 어휘집에 모두 같은 어근 혹은 어간을 중심으로 저장되어 있다는 것이다. 두 번째 가설은 어간이나 어근으로의 분석을 통해 활용된 단어를 이해하는 것이 아니라 일단 활용된 형태의 어휘를 심성 어휘집에서 찾고, 만일 해당되는 것이 발견되면, 그 활용된 어절의 이해가 끝나게 되고, 만일에 해당되는 것이 심성 어휘집에 존재하지 않는 경우에만 부수적인 과정으로 구성 형태소로의 분석이 이루어진다는 것이다. 세 번째 가설은 어휘의 품사, 어휘의 빈도, 형태소 활용의 규칙성 등에 따라 구성 형태소로의 분석을 통해 활용된 단어를 이해하거나 아니면 활용된 어휘의 직접적인 접근을 통해 활용된 단어를 이해한다는 것이다. 본 연구에서는 이 세 종류의 가설 중에 어느 가설이 옳은 것인지를 조사하기 위해, "먹은" 흑은 "쥐어"와 같은 한국어 어절을 이용하여 형태소 표상 양식과 이해 과정을 다루었다. 본 연구의 목적을 위해 점화 어휘 판단 과제(primed-lexical decision task)를 사용하였다. 실험 1은 "먹은"처럼 동사 "먹다"로도 해석이 가능하고 명사 "먹"으로도 가능한 중의적 어절을 점화 문자열로 제시하고 이 문자열이 두 의미와 관련된 목표 단어 재인에 어떤 영향을 끼치는지를 조사하였다. 만일에 "먹"이라는 어근 혹은 어간으로의 분석을 통해 이 어절을 이해한다면 두 종류의 의미와 관련된 조건 모두에서 촉진적 점화 효과(facilitatory priming effect)가 나타날 것이고, 어절 전체로의 어휘 접근 과정이 일어난다면 사용빈도에서 높은 동사 뜻과 관련된 조건에서만 촉진적 점화 효과가 나타날 것이다. 실험 1의 결과는 두 종류의 의미가 모두 활성화되는 것을 보여 주었다. 즉, "먹은"과 간은 어절 이해는 구성 형태소로의 분석과 구성 형태소 어휘 접근을 통해 어절 이해가 이루어진다는 가설을 지지하고 있다. 실험 2에서는 실험 1과 다르게 한 뜻으로만 안일 수밖에 없는 "쥐어"와 같은 어절을 사용하여 이런 경우에도(즉, 어절의 문맥이 특정 뜻으로 한정하는 경우) 구성 형태소로의 분석 과정이 일어나는지를 조사하였다. 실험 2의 결과는 실험 1의 결과와는 다르게 어간의 한가지 의미와 관련된 조건만 촉진적 점화 효과가 나타나는 것을 보여주었다. 특히, 실험 2에서 SOA가 1000msec일 경우, 두 의미의 활성화가 나타나는 것을 보여주었는데, 이 같은 결과는 어절 문맥이 특정한 의미로 한정시킬 경우는 심성어휘집에 활용형태로 들어있다는 것이다. 또한 명칭성 실어증 환자의 경우에는 즉시적 점화과제에서는 일반인과 같은 형태소 처리과정을 보였으나, 그이후의 처리과정이 일반인과 다른 형태를 보였다. 실험 1과 실험 2의 결과는 한국어 어절 분석이 구문분석 또는 활용형태를 통해 어휘 접근되는 가설을 지지하고 있다. 또 명칭성 실어증 환자의 경우에는 지연된 점화과제에서 형태소 처리가 일반인과 다르다는 것이 밝혀졌다. 이 결과가 옳다면 한국의 심성 어휘집은 어절 문맥에 따라서 어간이나 어근 또는 활용형 그 자체로 이루어져 있을 것이다.

• Sleep Medicine and Psychophysiology
• /
• v.27 no.2
• /
• pp.67-76
• /
• 2020

Objectives: Brain maturation involves brain lateralization and asymmetry to achieve efficient information processing and cognitive controls. This study elucidates normal brain maturation change during the gap between ages 6-9 and age 14-17 using resting EEG. Methods: An EEG dataset was acquired from open source MIPDB (Multimodal Resource for Studying Information Processing in the Developing Brain). Ages 6-9 (n = 24) and ages 14-17 (n = 26) were selected for analysis, and subjects with psychiatric illness or EEG with severe noise were excluded. Finally, ages 6-9 (n = 14) and ages 14-17 (n = 11) were subjected to EEG analysis using EEGlab. A 120-sec length of resting EEG when eyes were closed was secured for analysis. Brain topography was compartmentalized into nine regions, best fitted with brain anatomical structure. Results: Absolute power of the delta band and theta band in ages 6-9 was greater than that of ages 14-17 in the whole brain, and, also is relative power of delta band in frontal compartment, which is same line with previous studies. The relative power of the beta band of ages 14-17 was greater than that of ages 6-9 in the whole brain. In asymmetry evaluation, relative power of the theta band in ages 14-17 showed greater power in the left than right frontal compartment; the opposite finding was noted in the parietal compartment. For the alpha band, a strong relative power distribution in the left parietal compartment was observed in ages 14-17. Absolute and relative power of the alpha band is distributed with hemispheric left lateralization in ages 14-17. Conclusion: During the gap period between ages 6-9 and ages 14-17, brain work becomes more complicated and sophisticated, and alpha band and beta band plays important roles in brain maturation in typically developing children.

• The Korean Journal of Nuclear Medicine
• /
• v.34 no.1
• /
• pp.10-21
• /
• 2000

Purpose: Episodic memory is described as an 'autobiographical' memory responsible for storing a record of the events in our lives. We performed functional brain activation study using ${H_2}^{15}O$ PET to reveal the neural basis of the encoding and the retrieval of episodic memory in human normal volunteers. Materials and Methods: Four repeated ${H_2}^{15}O$ PET scans with two reference and two activation tasks were performed on 6 normal volunteers to activate brain areas engaged in encoding and retrieval with verbal materials. Images from the same subject were spatially registered and normalized using linear and nonlinear transformation. Using the means and variances for every condition which were adjusted with analysis of covariance, t-statistic analysis were performed voxel-wise. Results: Encoding of episodic memory activated the opercular and triangular parts of left inferior frontal gyrus, right prefrontal cortex, medial frontal area, cingulate gyrus, posterior middle and inferior temporal gyri, and cerebellum, and both primary visual and visual association areas. Retrieval of episodic memory activated the triangular part of left inferior frontal gyrus and inferior temporal gyrus, right prefrontal cortex and medial temporal area, and both cerebellum and primary visual and visual association areas. The activations in the opercular part of left inferior frontal gyrus and the right prefrontal cortex meant the essential role of these areas in the encoding and retrieval of episodic memory. Conclusion: We could localize the neural basis of the encoding and retrieval of episodic memory using ${H_2}^{15}O$ PET, which was partly consistent with the hypothesis of hemispheric encoding/retrieval asymmetry.

• The Korean Journal of Nuclear Medicine
• /
• v.38 no.3
• /
• pp.233-240
• /
• 2004

Purpose: We developed a computer-aided classifier using artificial neural network (ANN) to discriminate the cerebral metabolic pattern of medial and lateral temporal lobe epilepsy (TLE). Materials and Methods: We studied brain F-18-FDG PET images of 113 epilepsy patients sugically and pathologically proven as medial TLE (left 41, right 42) or lateral TLE (left 14, right 16). PET images were spatially transformed onto a standard template and normalized to the mean counts of cortical regions. Asymmetry indices for predefined 17 mirrored regions to hemispheric midline and those for medial and lateral temporal lobes were used as input features for ANN. ANN classifier was composed of 3 independent multi-layered perceptrons (1 for left/right lateralization and 2 for medial/lateral discrimination) and trained to interpret metabolic patterns and produce one of 4 diagnoses (L/R medial TLE or L/R lateral TLE). Randomly selected 8 images from each group were used to train the ANN classifier and remaining 51 images were used as test sets. The accuracy of the diagnosis with ANN was estimated by averaging the agreement rates of independent 50 trials and compared to that of nuclear medicine experts. Results: The accuracy in lateralization was 89% by the human experts and 90% by the ANN classifier Overall accuracy in localization of epileptogenic zones by the ANN classifier was 69%, which was comparable to that by the human experts (72%). Conclusion: We conclude that ANN classifier performed as well as human experts and could be potentially useful supporting tool for the differential diagnosis of TLE.