Biomedical subjects

Myung Sun Kim

Publications and source records attributed to Myung Sun Kim.

7 recordsLinked to original sources

PubMed2006

Kinematic study following double-bundle, anterior cruciate ligament reconstruction.

The purpose of this study was to evaluate tibiofemoral kinematics after double-bundle anterior cruciate ligament (ACL) reconstructions and compare them with those of successful single-bundle reconstructions and contralateral normal knees using open MR images. We obtained MR images based on the flexion angle without weight-bearing, from 20 patients with successful unilateral single-bundle (10 patients) and double-bundle (10 patients) ACL reconstructions with tibialis anterior allografts and a minimum 1-year follow-up. The MR images of the contralateral uninjured knees were used as normal controls. Sagittal images of the mid-medial and mid-lateral sections of the tibiofemoral compartments were used to measure the translation of the femoral condyles relative to the tibia. The mean translations of the medial femoral condyles on the tibial plateaus during knee joint motion showed no significant differences among normal, single-bundle, and double-bundle ACL reconstructed knees (all p>0.05). The mean translations of the lateral femoral condyles showed a significant difference between normal and single-bundle reconstructed knees, or between single-bundle and double-bundle reconstructed knees (p<0.05). However, there was no significant difference between normal and double-bundle reconstructed knees (p=0.220). These findings suggest that double-bundle ACL reconstruction restores normal kinematic tibiofemoral motion better than single-bundle reconstruction.

Anterior Cruciate Ligament↗

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

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

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

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

Hypothermia protects against endotoxin-induced acute lung injury in rats.

OBJECTIVE: Hypothermia in humans and animals is known to decrease the number and function of circulating neutrophils. Because an activation of circulating neutrophils and their sequestration into the lung are important pathogenetic phenomena in endotoxin-associated lung injury, we conjectured that hypothermia could prevent this type of lung injury. DESIGN AND SETTING: Animal study at a university-affiliated research institute. SUBJECTS: Thirty-six Sprague-Dawley rats. INTERVENTIONS: After anesthesia, the rats were randomly assigned to normothermia (37 degrees C, rectal temperature) or hypothermia (27 degrees C), which was induced by surface cooling. After 1 h of stable temperature, the rats were administered intratracheal doses of lipopolysaccharide (LPS; 3 mg/kg) (normothermia-LPS; hypothermia-LPS) or an equivalent volume of normal saline (normothermia-saline; hypothermia-saline). The rectal temperature was maintained within +/-1 degrees C of the target temperature for 6 h after the intratracheal treatment. MEASUREMENTS AND RESULTS: Compared with the normothermia-LPS group, the neutrophil count in bronchoalveolar lavage (BAL) fluid (p=0.002) and the myeloperoxidase activity of lung tissues (p=0.002) of the hypothermia-LPS group were both lower. Compared with the normothermia-LPS group, the BAL interleukin-1beta level of the hypothermia-LPS group was lower (p<0.001), whereas the BAL interleukin-10 level of the hypothermia-LPS group was higher (p=0.026). Compared with the normothermia-LPS group, the histologic scores for acute lung injury of the hypothermia-LPS group were lower (p=0.007). CONCLUSIONS: Hypothermia pretreatment decreased the pulmonary sequestration of neutrophils, induced a favorable balance between pro- and anti-inflammatory cytokines, and attenuated histologic injury in endotoxin-challenged rats.

Acute Disease↗

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↗