Biomedical subjects

Jun Soo Kwon

Publications and source records attributed to Jun Soo Kwon.

At least 55 records · Page 3Linked to original sources

PubMed2004

Analysis of the hemispheric asymmetry using fractal dimension of a skeletonized cerebral surface.

We investigated hemispheric asymmetry using the fractal dimension (FD) of the skeletonized cerebral surface. Sixty-two T1-weighted magnetic resonance imaging volumes from normal Korean adults were used. The skeletonization of binary volume data, which corresponded to the union of the gray matter and cerebrospinal flow classified by fuzzy clustering, was performed slice by slice in the sagittal direction, and then skeletonized slices were integrated into the three-dimensional (3-D) hemisphere. Finally, the FD of the 3-D skeletonized cerebral surface was calculated using the box-counting method. We measured the FD of the skeletonized cerebral surface and the volumes of intracranial gray matter and white matter for the whole hemispheres and obtained the hemispheric asymmetries of each measurement. The FD, the gray matter, and the white matter volumes for the whole hemispheres decreased in the old group. The asymmetry of the FD revealed a significant right-greater-than-left asymmetry showed rightward, but did not change according to age and gender. None of the intracranial gray matter or white matter volumes showed any significant asymmetric changes. It could be said that the FD of the skeletonized cerebral surface is a novel measure of cerebral asymmetry.

Adolescent↗

PubMed2004

Association between EEG alpha power and visuospatial function in obsessive-compulsive disorder.

The purpose of the present paper was to determine if frontal activity, measured as electroencephalogram alpha power, correlates with visuospatial functions in obsessive-compulsive disorder (OCD). Electroencephalography and the Rey-Osterrieth Complex Figure Test (RCFT) were performed on 23 patients meeting the Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) OCD criteria. After quantitatively analyzing EEG recordings taken over the frontal, temporal, parietal and occipital regions (F1, F2, T3, T4, P3, P4, O1 and O2), the log transformed absolute power values of the alpha frequencies of the regions were regressed with each RCFT index (copy, immediate recall and delayed recall score). On the frontal region (F1, F2), the RCFT copy score was found to be correlated with the alpha power with regression coefficients that had different directions according to hemisphere (F1, 5.62; F2, -5.26). The result that visuo-constructional ability represented by the RCFT copy score correlated with frontal activation as measured by decreased alpha power, supports the opinion that visuospatial dysfunction in OCD is not in the visuospatial memory per se but rather that it is mediated by executive function deficit. The opposite correlation directions indicate that greater left frontal activation correlates with a poorer RCFT copy score and that greater right frontal activation correlates with a better copy score. These relationships provide indirect evidence of the possibility that the main pathology of OCD is located in the left hyperfrontality and that the right hyperfrontality of OCD occurs by a compensatory mechanism.

Adult↗

PubMed2004

Impairment of recognition memory in schizophrenia: event-related potential study using a continuous recognition task.

Recognition memory and the dissociation of immediate and delayed repetition in schizophrenic patients were investigated using event-related potential (ERP) and a continuous word recognition task. In total, 14 schizophrenic patients and 14 age and gender-matched control subjects, were recruited. Among 240 stimulus words used, 40 words were not repeated, 100 were repeated immediately, and 100 were repeated after five intervening words. Both schizophrenic and control groups responded faster to words repeated immediately than to words repeated after a delay and to new words. However, schizophrenic patients responded less accurately to words repeated immediately and to words repeated after a delay than the controls. In terms of ERP, schizophrenic patients showed significantly reduced N200, late positive component (LPC), and N400 amplitudes, and a more frontally-distributed N200 topography than the controls. For controls, immediate repetition was associated with a large LPC amplitude and the absence of N400, while delayed repetition was associated with a small LPC amplitude and the presence of N400. However, this dissociation between immediate and delayed repetition was not observed in schizophrenic patients. All of these results suggest that schizophrenic patients have recognition memory impairment, the cause of which may range from early encoding, and memory search to late retrieval.

Adult↗

PubMed2004

Volumetric investigation of the frontal-subcortical circuitry in patients with obsessive-compulsive disorder.

The pathophysiology of obsessive-compulsive disorder (OCD) is thought to involve disturbance of the frontal-subcortical circuitry. To investigate the morphological characteristics of this circuitry, we examined the volume of the orbitofrontal cortex, anterior cingulate, thalamus, caudate, and the putamen in 36 age- and sex-matched OCD patients and normal control subjects using three-dimensional magnetic resonance (MR) brain imaging. The left orbitofrontal volumes were found to be significantly smaller in the OCD patients and showed significant negative correlations with obsessive-compulsive symptom severity. These findings suggest that a structural abnormality of this brain region is implicated in the pathophysiology of OCD.

Adult↗

PubMed2003

Neuropsychological correlates of P300 abnormalities in patients with schizophrenia and obsessive-compulsive disorder.

The cognitive significance of P300 abnormalities in schizophrenia and obsessive-compulsive disorder (OCD) was investigated. P300 was measured by an auditory oddball paradigm, in which a series of standard tones (1000 Hz) and target tones (1500 Hz) were presented. The subject's task was to count the number of the presented target tones. Cognitive functions were evaluated by neuropsychological tests, which were chosen to be sensitive to frontal and temporal dysfunction. Twenty-two schizophrenic patients, 19 OCD patients and 21 healthy controls participated. Event-related potentials measured at 15 electrode sites, which consisted of five levels on the left-right dimension and three levels on the anterior-posterior dimension, were included in the statistical analysis. P300 amplitudes on all 15 electrode sites were significantly smaller in schizophrenic and OCD patients than in the controls. Schizophrenic patients performed poorly on almost all neuropsychological tests, while OCD patients showed impaired performance on the Rey-Osterrieth Complex Figure Test and on a controlled oral word association test. In schizophrenic patients, P300 amplitude was associated with performance on verbal memory and learning by the Luria-Nebraska Neuropsychological Battery, while for OCD patients, P300 amplitude was related to the Trail Making Test, Part B response time. These results indicate that schizophrenic patients have generalized cognitive impairments, which are substrated by a wide range of cortical dysfunctions. The major cognitive deficits observed in OCD patients were impairments of controlled attention and self-guided, flexible behavior, which are mediated by the fronto-striatal system. The neurophysiological mechanisms underlying P300 abnormalities observed in schizophrenic and OCD patients are discussed.

Acoustic Stimulation↗

PubMed2003

Morphometric abnormality of the insula in schizophrenia: a comparison with obsessive-compulsive disorder and normal control using MRI.

The insula is increasingly the subject of great interest in psychiatric disorders of neurodevelopmental origin because of its anatomical location, wide interconnectivity, and variety of functions. This study explores the possible morphometric change of the insula in schizophrenia and obsessive-compulsive disorder (OCD), and its potential relationship to clinical symptoms. The insula was traced on all coronal slices of magnetic resonance images of three age- and sex-matched diagnostic groups, which consisted of 21 patients with schizophrenia, 21 patients with OCD and 21 normal volunteers. The volumetric measures of the insula were compared among the three groups, and their relationships to the symptom severity were investigated. Volumetric reduction of the left insula was observed in the schizophrenia group, but not in the OCD group. These results confirm the involvement of deficient insular function in the pathophysiology of schizophrenia.

Adult↗

PubMed2003

Altered hemispheric asymmetry and positive symptoms in schizophrenia: equivalent current dipole of auditory mismatch negativity.

The abnormality of mismatch negativity (MMN) in schizophrenia is thought to be associated with perceptional disturbance and cognitive dysfunction. The purpose of the present study was to investigate the change of the normal functional hemispheric lateralization in schizophrenia by employing the equivalent current dipole (ECD) model of auditory MMN with individual MRI and high-density electroencephalography (EEG). The MMNs resulting from auditory stimuli with passive oddball paradigm in a group of schizophrenics (n = 15), and also a group of age-, sex-, and handedness-matched normal controls, were recorded by 128 channel EEG. The location and power of ECD sources at the peak point were calculated. Individual 3-D brain magnetic resonance images (MRI) were used for realistic head modeling and for source localization. For both groups, the MMN source was determined to be located in the superior temporal gyrus (STG). However, the normal functional hemispheric asymmetry of ECD power was significantly altered in the schizophrenics (chi(2) test = 16.13, p < 0.001). Left MMN ECD power and the asymmetry coefficient (AC) were negatively correlated with the positive scores from Positive and Negative Syndrome Scale (PANSS) (r = -0.673, p = 0.008), especially with the hallucinatory behavior subscale (r = -0.677, p = 0.008). These findings support the deficits in preattentive automatic processing of auditory stimuli, especially in the left hemisphere, and indicate the correlation between positive symptoms, especially auditory hallucination, and left temporal lobe dysfunction in schizophrenia.

Adult↗

PubMed2003

Neural correlates of clinical symptoms and cognitive dysfunctions in obsessive-compulsive disorder.

Although results from neuropsychological and neuroimaging studies have postulated the involvement of the frontal lobe and the subcortical brain regions in the pathophysiology of obsessive-compulsive disorder (OCD), neuroimaging studies have provided little evidence that cognitive abnormalities in patients with OCD are related to dysfunctions in these areas. This study was designed to determine whether the clinical features and cognitive deficits of OCD might be taken to reflect frontal-subcortical dysfunction. Fourteen patients with OCD and 14 case-matched normal subjects completed clinical and cognitive evaluation, including four sets of neuropsychological tests that assessed the executive functions and visual memory. Cerebral glucose metabolic rates were measured by using positron emission tomography (PET) with 18F-fluorodeoxyglucose. Behavioral and PET data were analyzed using statistical parametric mapping for group differences and behavioral-metabolic correlates. The right orbitofrontal cortex showed increased metabolic activity and the left parieto-occipital junction showed decreased metabolic activity in patients. Metabolism in the right hippocampus, the left putamen and the right parietal region was associated with the severity of obsessive-compulsive symptoms. Correlations between metabolic rates and neuropsychological test scores in the prefrontal cortex and the putamen occurred only in the patient group. These results suggest that patients with OCD have distinct features of brain metabolic activities for performing cognitive tasks as well as presenting obsessive-compulsive symptoms. In particular, the frontal-subcortical circuits might mediate not only symptomatic expression but also cognitive expression in patients with OCD.

Adult↗

PubMed2003

Independent component model for cognitive functions of multiple subjects using [15O]H2O PET images.

An independent component model of multiple subjects' positron emission tomography (PET) images is proposed to explore the overall functional components involved in a task and to explain subject specific variations of metabolic activities under altered experimental conditions utilizing the Independent component analysis (ICA) concept. As PET images represent time-compressed activities of several cognitive components, we derived a mathematical model to decompose functional components from cross-sectional images based on two fundamental hypotheses: (1) all subjects share basic functional components that are common to subjects and spatially independent of each other in relation to the given experimental task, and (2) all subjects share common functional components throughout tasks which are also spatially independent. The variations of hemodynamic activities according to subjects or tasks can be explained by the variations in the usage weight of the functional components. We investigated the plausibility of the model using serial cognitive experiments of simple object perception, object recognition, two-back working memory, and divided attention of a syntactic process. We found that the independent component model satisfactorily explained the functional components involved in the task and discuss here the application of ICA in multiple subjects' PET images to explore the functional association of brain activations.

Adult↗

PubMed2003

LORETA imaging of P300 in schizophrenia with individual MRI and 128-channel EEG.

We investigated the characteristics of P300 generators in schizophrenics by using voxel-based statistical parametric mapping of current density images. P300 generators, produced by a rare target tone of 1500 Hz (15%) under a frequent nontarget tone of 1000 Hz (85%), were measured in 20 right-handed schizophrenics and 21 controls. Low-resolution electromagnetic tomography (LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Three-dimensional current density images were reconstructed from the LORETA intensity maps that covered the whole cortical gray matter. Spatial normalization and intensity normalization of the smoothed current density images were used to reduce anatomical variance and subject-specific global activity and statistical parametric mapping (SPM) was applied for the statistical analysis. We found that the sources of P300 were consistently localized at the left superior parietal area in normal subjects, while those of schizophrenics were diversely distributed. Upon statistical comparison, schizophrenics, with globally reduced current densities, showed a significant P300 current density reduction in the left medial temporal area and in the left inferior parietal area, while both left prefrontal and right orbitofrontal areas were relatively activated. The left parietotemporal area was found to correlate negatively with Positive and Negative Syndrome Scale total scores of schizophrenic patients. In conclusion, the reduced and increased areas of current density in schizophrenic patients suggest that the medial temporal and frontal areas contribute to the pathophysiology of schizophrenia, the frontotemporal circuitry abnormality.

Adolescent↗

PubMed2003

N-methyl-D-aspartate receptor in working memory impairments in schizophrenia: event-related potential study of late stage of working memory process.

Working memory (WM) deficit in schizophrenic patients has been well established. Still, underlying biological substrate of the impairment is not clear. Among neurotransmitter hypotheses of schizophrenia, N-methyl-D-aspartate (NMDA) receptor model is mostly supported, considering that NMDA receptor antagonist can elicit both psychosis and cognitive impairment observed in schizophrenic patients. In current study, to test the neuropsychological and the electrophysiological effects of NMDA receptor in WM, event-related potentials (ERPs) of Sternberg's short-term memory scanning task (SMST) were analyzed in 10 healthy subjects under intravenous administration of a subanesthetic dose of ketamine (0.65 mg/kg/h) or placebo (normal saline). Late positive component (LPC) of ERP was hypothesized to reflect later stage of WM. Brief Psychiatric Rating Scale score was significantly increased (t=-5.75, df=9, P<.001) and correct response rate was significantly decreased (t=2.21, df=9, P=.054) after ketamine administration. Neither reaction time nor LPC latency, which reflect memory scanning time, was changed. Amplitude of LPC was significantly reduced after ketamine administration (z=-2.31, number of observations=120, P=.021). In conclusion, NMDA receptor antagonist administration elicited WM deficit both in behavioral and electrophysiological level. Electrophysiological component reflecting later stage of WM was impaired by NMDA antagonist.

Adult↗

PubMed2003

Optimized individual mismatch negativity source localization using a realistic head model and the Talairach coordinate system.

The purpose of this study is to evaluate the difference between anatomical locations of mismatch negativity (MMN) generators using a realistic head model and the Talairach coordinate system. This was performed by dipole source analysis by using a high density 128 channel electroencephalography (EEG) acquisition system and the subjects' individual 3D magnetic resonance images (MRI) for the realistic head model, in 24 healthy subjects. For dipole source localization, both the Talairach coordinate system and the individual MRI realistic head models were used and location results were compared. The MMN generators were clearly localized in the superior temporal gyri, especially in Heschl's gyrus, according to each individual's structural MRI. Only 37.5% of subjects showed the same anatomical locations of the MMN generator in both hemispheres in the realistic head model and in Talairach coordinate system, but fifteen subjects (62.5%) didn't. This result indicates that individually registered functional locations are desirable for the precise localization of activated areas in functional imaging studies and that a brain coordinate system is needed which adequately accounts for ethnic differences.

Acoustic Stimulation↗

PubMed2003

Classification of frequency distributions of diagnostic criteria scores in twelve personality disorders by the curve fitting method.

The purpose of the present study was to investigate whether each personality disorder (PD) has a different frequency distribution of diagnostic criteria, and to classify the distribution of each PD on the basis of shape by the curve fitting method. A total of 4740 male subjects in early adulthood completed the Korean version of the Personality Diagnostic Questionnaire (4th revision; PDQ-4+). The frequency distribution of scores in each PD was specified to the best fitted model by the curve estimation procedure. Twelve distributions of PD criteria were fitted to three types of curve models (quadratic, cubic, and logistic). The quadratic model included obsessive-compulsive and histrionic PD. The cubic model included borderline, narcissistic, avoidant, passive-aggressive, paranoid, and schizotypal PD. The logistic model contained dependent, depressive, schizoid, and antisocial PD. The results suggest that each PD has a different type of distribution and each distribution of PD might be classified to a specific curve model. Also, the results suggest that the issue of continuities between PD and the normal group could not be generalized to all PD, but should be considered individually for each PD.

Adult↗

PubMed2003

Modified magnetic resonance image based parcellation method for cerebral cortex using successive fuzzy clustering and boundary detection.

Development of the accurate and reproducible parcellation of the human brain can be used to resolve the complex structure-functional relationships in the brain. We propose a modified parcellation method that provides the reliable and reproducible regions of interest using successive fuzzy c-means (sFCM) and boundary-detection algorithm. This method displays simultaneously both original brain image for identifying the sulcal landmarks and its tissue-classified image for referring to patterns of sulci. The whole cerebral region is extracted by the semiautomated region growing method and then classified to gray matter, white matter, and cerebrospinal fluid by sFCM. Referred to the other previous researches, the volume ratio of gray matter to white matter was shown to find that the efficiency of classification was improved (conventional FCM: 0.80 +/- 0.12 vs. sFCM: 1.57 +/- 0.18). Inter-rater reliability, estimated by the regression analysis, demonstrated that the proposed method was more reliable and reproducible than conventional methods [ANALYZE: correlation coefficient (CC)=0.341, Sig.=0.335 vs. proposed method: CC=0.816, Sig.=0.004]. The volume ratio of the whole cerebrum to the parceled object can be used to investigate structural abnormalities for the pathological detection of the various mental diseases such as schizophrenia, obsessive-compulsive disorder.

Algorithms↗

PubMed2003

Functional disconnection between the prefrontal and parietal cortices during working memory processing in schizophrenia: a[15(O)]H2O PET study.

OBJECTIVE: The prefrontal-parietal circuits have been reported to play an important role in working memory. The purpose of this study was to use direct neuroimaging to address whether interregional correlation in the prefrontal-parietal circuits is impaired in schizophrenia. METHOD: [(15)O]H(2)O positron emission tomography was used to compare regional blood flow changes in 12 schizophrenic and 12 healthy comparison subjects during the n-back sequential-picture working memory task. Interregional correlation was assessed by correlating the regional activation of the lateral prefrontal area with that of other activated areas in each subject group. RESULTS: Dorsolateral prefrontal activation was observed around the right superior frontal sulcus in the healthy subjects, and ventrolateral prefrontal activation below the right inferior frontal sulcus was observed in the schizophrenic patients. Activation in the right lateral prefrontal cortex was significantly correlated with activation in the bilateral inferior parietal region in the healthy subjects but was not correlated with any regional activation in the patients. CONCLUSIONS: The findings suggest prefrontal-parietal functional disconnection, particularly prefrontal dissociation and abnormal prefrontal-parietal interaction, during working memory processing in schizophrenia.

Adult↗

PubMed2002

Decrease in genu of the corpus callosum in medication-naïve, early-onset dysthymia and depressive personality disorder.

BACKGROUND: The purpose of this study was to detect differences in regional areas of the corpus callosum (CC) in subjects with early-onset minor depression (dysthymia or depressive personality disorder) and healthy comparison subjects. Based on previous reports that have suggested reduced frontal lobe volume and reduced hemispheric lateralization in the frontal regions of the brain in depression, we hypothesized that the area of the CC that interconnects the frontal regions of the brain, i.e., the genu, will be smaller compared to that of healthy comparison subjects. METHODS: Forty female subjects with early-onset dysthymia or depressive personality disorder, as defined by the Structured Clinical Interview for DSM-III-R and the Diagnostic Interview for Depressive Personality, respectively, and age- and gender-matched healthy comparison subjects (n = 42) were recruited (age: 21.4 +/- 2.1 and 20.9 +/- 2.8 years, respectively). All subjects were psychotropic medications-naïve and right-handed. A 1.5T GE Sigma scanner was used to acquire 124 1.5-mm-thick contiguous coronal images. Midsagittal slice images were carefully selected from reconstructed magnetic resonance images both from native and stereotaxic space to measure seven regional areas of the CC. RESULTS: There were significant diagnosis by CC region interactions [F(6,480) = 4.06, p <.001; F(6,480) = 3.30, p =.003, native and stereotaxic space, respectively]. Early-onset minor depression subjects had a 9.9% (native space) and 6.9% (stereotaxic space) smaller genu of the CC compared to the healthy comparison subjects (the Newman-Keuls post hoc test, p =.005 and.019, native and stereotaxic space, respectively). Early-onset minor depression subjects also had a 7.8% smaller posterior midbody relative to the comparison subjects (the Newman-Keuls post hoc test, p =.033) only in the native space. Severity of current depressive symptoms or duration of illness did not correlate with the size of the genu or the posterior midbody parts of the CC. CONCLUSIONS: These results suggest frontal lobe structural, and possibly functional, abnormalities in the brain in young female adults with a milder spectrum of depression, i.e., DSM-IV early-onset dysthymia or depressive personality disorder. The present findings point out the possible role of frontal lobe abnormality in pathophysiology of early-onset minor depression.

Adolescent↗

PubMed2002

Statistical parametric mapping of LORETA using high density EEG and individual MRI: application to mismatch negativities in schizophrenia.

We describe a method for the statistical parametric mapping of low resolution electromagnetic tomography (LORETA) using high-density electroencephalography (EEG) and individual magnetic resonance images (MRI) to investigate the characteristics of the mismatch negativity (MMN) generators in schizophrenia. LORETA, using a realistic head model of the boundary element method derived from the individual anatomy, estimated the current density maps from the scalp topography of the 128-channel EEG. From the current density maps that covered the whole cortical gray matter (up to 20,000 points), volumetric current density images were reconstructed. Intensity normalization of the smoothed current density images was used to reduce the confounding effect of subject specific global activity. After transforming each image into a standard stereotaxic space, we carried out statistical parametric mapping of the normalized current density images. We applied this method to the source localization of MMN in schizophrenia. The MMN generators, produced by a deviant tone of 1,200 Hz (5% of 1,600 trials) under the standard tone of 1,000 Hz, 80 dB binaural stimuli with 300 msec of inter-stimulus interval, were measured in 14 right-handed schizophrenic subjects and 14 age-, gender-, and handedness-matched controls. We found that the schizophrenic group exhibited significant current density reductions of MMN in the left superior temporal gyrus and the left inferior parietal gyrus (P < 0. 0005). This study is the first voxel-by-voxel statistical mapping of current density using individual MRI and high-density EEG.

Adolescent↗

PubMed2002

Dissociation of working memory processing associated with native and second languages: PET investigation.

Verbal working memory plays a significant role in language comprehension and problem-solving. The prefrontal cortex has been suggested as a critical area in working memory. Given that domain-specific dissociations of working memory may exist within the prefrontal cortex, it is possible that there may also be further functional divisions within the verbal working memory processing. While differences in the areas of the brain engaged in native and second languages have been demonstrated, little is known about the dissociation of verbal working memory associated with native and second languages. We have used H2(15)O positron emission tomography in 14 normal subjects in order to identify the neural correlates selectively involved in working memory of native (Korean) and second (English) languages. All subjects were highly proficient in the native language but poorly proficient in the second language. Cognitive tasks were a two-back task for three kinds of visually presented objects: simple pictures, English words, and Korean words. The anterior portion of the right dorsolateral prefrontal cortex and the left superior temporal gyrus were activated in working memory for the native language, whereas the posterior portion of the right dorsolateral prefrontal cortex and the left inferior temporal gyrus were activated in working memory for the second language. The results suggest that the right dorsolateral prefrontal cortex and left temporal lobe may be organized into two discrete, language-related functional systems. Internal phonological processing seems to play a predominant role in working memory processing for the native language with a high proficiency, whereas visual higher order control does so for the second language with a low proficiency.

Adult↗