Biomedical subjects

Tae Hyon Ha

Publications and source records attributed to Tae Hyon Ha.

13 recordsLinked to original sources

PubMed2006

An MRI study of structural variations in schizophrenia using deformation field morphometry.

Magnetic resonance imaging (MRI) has an important role in investigating the changes in brain structure that are associated with schizophrenia. In this study, MRI scans of patients diagnosed with schizophrenia (37 males; 19 females; 17-42 years of age) were compared with those of an age- and sex-matched group of normal subjects (37 males; 19 females; 18-40 years of age). Based on the images of the healthy control subjects, we constructed a representative average brain template. Automated image analysis techniques were used to measure differences in the regional nonlinear deformation fields between the two groups. A deformation field, which measures the spatial transformation to deform a template of brain anatomy to each individual data, was obtained as a three-dimensional displacement vector in each voxel. There was a significantly greater magnitude of the deformation fields in the superior frontal and parietal lobes as well as in the cingulate gyrus connecting both lobes of the patients with schizophrenia than in those of healthy controls, suggesting that these cerebral regions have a significantly higher structural variability in schizophrenia.

Adolescent↗

PubMed2006

Increased water diffusivity in the frontal and temporal cortices of schizophrenic patients.

Schizophrenia has been suggested to be the result of both macroscopic and microscopic abnormalities in the brain. Although no definitive clinico-pathological correlations have been found to reconcile the many facets inherent in this disorder, the recent development of the magnetic resonance diffusion tensor imaging (DTI) has allowed us to gather useful information regarding the microcircuitry of the brain. Specifically, the apparent diffusion coefficient (ADC) reflects the degree of diffusion barriers and heterosynaptic communication for the brain neurotransmitter. Nineteen patients with DSM-IV schizophrenia and 21 age- and sex-matched control subjects participated in DTI, and the severity of the patients' symptoms was evaluated according to the Positive and Negative Syndrome Scale (PANSS). The ADC values were determined and compared between patients and control subjects via voxel-based morphometry. The results show an increased ADC in the bilateral fronto-temporal regions of the schizophrenic patients, as compared with those of the control subjects. In addition, the ADC values in the area of the right insular were correlated with the negative syndromes from the PANSS. Our findings of increased water diffusivity in the fronto-temporal regions of schizophrenic patients and the correlation between negative symptom scales and the ADC in the right insular region indicate that damaged brain microcircuitry might contribute to the pathophysiology of schizophrenia. These findings contribute towards integrating micro and macrostructural abnormalities and syndromes of schizophrenia.

Adult↗

PubMed2006

Effect of cognitive training focusing on organizational strategies in patients with obsessive-compulsive disorder.

The purpose of the present paper was to develop a cognitive training program for patients with obsessive-compulsive disorder (OCD) and evaluate its effectiveness. Nine 60-min sessions focusing on the improvement of organizational strategies were given to 15 patients with OCD over a period of 5 weeks. The control group consisted of 15 age- and sex-matched patients also with OCD. The Rey-Osterrieth Complex Figure Test and Korean-California Verbal Learning Test were administered before and after cognitive training. Clinical symptoms were assessed with the Yale-Brown Obsessive-Compulsive Scale. The memory function in the treatment group improved and their clinical symptoms were alleviated after training, compared to those of the control group. Cognitive training of OCD patients not only improved their memory function, but also alleviated their clinical symptoms. Therefore, cognitive training, focusing on the improvement of organizational strategies, could be an effective treatment modality for patients with OCD.

Activities of Daily Living↗

PubMed2005

Implicit and explicit memory in patients with obsessive-compulsive disorder: an event-related potential study.

The implicit and explicit memory in patients with obsessive-compulsive disorder (OCD) was investigated using the event-related potential (ERP). For the assessment of implicit memory, a lexical decision task was administered. Among a total of 320 words and 140 non-words, 200 words were repeated, while the remaining 120 words and the 140 non-words were not repeated. For explicit memory, a continuous recognition task was administered, in which 280 words were repeated and 100 were not repeated. On the recognition task, both the controls and OCD patients showed more positivity to the old words than to the new words during the 200-600 ms period post-stimulus. Both groups showed faster response time to the old words than to the new words. On the lexical decision task, the controls showed the old/new effect during the 200-500 ms period post-stimulus, while the OCD patients did not. However, OCD patient showed faster response time to the old words than to the new words, although OCD patients showed prolonged response times to the old words compared to the controls. These results indicate that OCD patients have preserved explicit and implicit memory. The absence of old/new effect on ERP in OCD patients was discussed in terms of dysfunction of frontostriatal system, which plays an important role in both OCD and implicit memory.

Adult↗

PubMed2005

Sex differences in the human corpus callosum: diffusion tensor imaging study.

In order to assess underlying structural differences between the male and female corpus callosum, the fractional anisotropy and volume of the corpus callosum, and also its T1 signal intensity, were measured. The corpus callosum of the 15 normal women and 15 normal men was drawn on the mid-sagittal T1-weighted image, for determining its volume and signal intensity, and this region of interest was projected onto the coregistered fractional anisotropy image, in order to obtain the value for the corpus callosum. We found increased T1 signal intensity and decreased fractional anisotropy in the female corpus callosum, as compared with that of the male. Despite the long-standing debates, the corpus callosum remains a region of sex differences.

Adult↗

PubMed2005

Asymmetry analysis of deformable hippocampal model using the principal component in schizophrenia.

The hippocampus is thought to play an important role in learning and memory processing, and impairments in memory, attention, and decision making are found commonly in schizophrenia. Although many studies have reported decreases in hippocampal volume in the left hemisphere in schizophrenia, regionally specific hippocampal volume loss has not been revealed consistently using volume analysis. Recently, many studies have analyzed shape asymmetry using 3-D models; however, inconsistent results have been reported, mainly due to methodologic differences. We therefore used an active, flexible, deformable shape model for surface parameterization, and compared shape asymmetry based on principal component analysis (PCA) in the hippocampi of schizophrenic patients with those of the normal controls. Although the overall pattern of the statistical results did not change according to the number of principal components, the reconstructed results based on six major components were much more distinguishable. Although the left hemispheric hippocampal volume was larger than the right hemispheric was in this study, the difference was not significant. In shape asymmetry analysis, the right hemisphere hippocampus was bilaterally larger than the left hemisphere hippocampus was in the head of the superior CA1 and smaller in the tail and head of the inferior CA1. The asymmetry in the schizophrenia group was statistically smaller than that in the control group through reduction of the left hemisphere hippocampus volume.

Adult↗

PubMed2004

Gray matter abnormalities in paranoid schizophrenia and their clinical correlations.

Numerous imaging studies have shown structural brain abnormalities in schizophrenia. Recently, voxel-based morphometry enabled whole brain analysis beyond the regions of interest (ROI). Regional gray matter concentrations of magnetic resonance (MR) images from 35 patients with paranoid schizophrenia were compared with those from 35 age- and sex-matched controls, and their clinical correlations were explored using voxel-based morphometry. Gray matter concentrations in the patients were significantly reduced in the left insular and dorsolateral prefrontal regions, and bilaterally in the medial frontal, anterior cingulate, inferior frontal and superior temporal regions. On the other hand, gray matter concentrations in the bilateral cerebellum and right striatum were significantly increased in the patients compared with controls. A negative correlation between the score for the severity of 'lack of insight and judgment' and gray matter concentrations in the left posterior and right anterior cingulate and bilateral inferior temporal regions including the lateral fusiform gyri was found. These results suggest the important roles of the paralimbic structures in the pathophysiology of schizophrenia and the involvement of the perceptual and monitoring systems in the mechanism of insight.

Adult↗

PubMed2004

Deformable model with surface registration for hippocampal shape deformity analysis in schizophrenia.

Changes to the hippocampal structure have been reported as consistent structural abnormalities in schizophrenic patients and have been related to the learning and memory deficits in such patients. Although many magnetic resonance (MR) imaging studies have focused on the hippocampal volume, local structural changes were difficult to discriminate from normal neuroanatomical variations. 3D shape deformation analysis of the brain structure may reflect localized schizophrenic abnormalities. A deformable model, evolved from the ellipsoid to hippocampal surface, with 2562 vertexes, was developed to analyze the left and right hippocampus shapes in 22 schizophrenic patients and 22 healthy age and gender matched controls. One of the most critical issues in the shape analysis is the determination of homologous points between two objects. To determine more accurate corresponding points, an alignment procedure, consisting of coarse and fine steps, following a deformation process, was applied. The performance of the alignment process was tested using artificial data, to get the alignment error to within 3 degrees for each angle. A volume analysis indicated the hippocampal volume to be bilaterally reduced in schizophrenic patients compared to the normal controls, with a shape analysis showing a deformity pattern of the hippocampal surface. Bilateral inward deformities in the anterior and posterior hippocampus and a unilateral outward deformity in the right anterior hippocampus were observed, respectively.

Adult↗

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↗

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↗

PubMedDate not supplied

Fractal dimension of cerebral cortical surface in schizophrenia and obsessive-compulsive disorder.

Schizophrenia and obsessive-compulsive disorder (OCD) are assumed to be neurodevelopmental disorders. To examine the cortical patterns in the two disorders, three-dimensional fractal dimension (FD) of skeletonized cerebral cortical surface was estimated from magnetic resonance (MR) images of 50 patients with schizophrenia, 45 patients with OCD and 26 healthy normal controls. The schizophrenic group had a significantly smaller mean FD than OCD group, and the OCD group than normal controls. The FD revealed a significant interaction effect of group-by-hemisphere, and the FD asymmetry index distinguished the schizophrenic group from normal controls. In logistic regression models, the FD and CSF volume correctly classified 95.6% of the schizophrenics from the controls and 88.0% of the patients with OCD from the controls. In the control and schizophrenic groups, the FD was not associated with any of tissue volume measures. In the OCD group, however, the FD was significantly correlated with gray matter tissue volume and intracranial volume (ICV). The results of the present study suggest that three-dimensional FD of cortical surface may be a sensitive indicator for investigation of the structural brain abnormalities in mental disorders, especially those developmentally disturbed. Further studies to explore regional FD changes in mental disorders and clinical implications of the FD including diagnostic value should be performed in the future.

Adult↗