Biomedical subjects

Jae-Jin Kim

Publications and source records attributed to Jae-Jin Kim.

41 records · Page 3Linked to original sources

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↗

PubMed2002

Effects of organic matrix proteins on the interfacial structure at the bone-biocompatible nacre interface in vitro.

The biocompatibility and potential osteoinductivity of nacre have favored its use as a bone-grafting material. The present study is to investigate the interfacial structure at the bone-nacre interface resulting from organic matrix proteins, which emphasizes the mechanism of bone-bonding ability and biocompatibility of the shell tissues such as nacre and biogenic calcite. To understand the interfacial reaction, the zeta potential measurements, provide for a unique method to quantify the actual state of the interface in situ, were used for synthetic and biogenic calcium carbonate suspensions with respect to pH and the organic matrix as an additive. The zeta potentials and surface charge density show that the organic matrix proteins are main charge regulators, resulting in the stabilized tissue properties as compared with synthetic crystals. Also, in forming calcium carbonate crystals with the additives, the conformation of organic matrix has an important role in the understanding of the newly formed interfacial structure. The result provides the primary role of the organic matrix proteins in controlling the formation of interfacial structure and biocompatibility with bone as well as the stability of biogenic tissues. And it gives a new insight into the usefulness of zeta potential measurement to describe the in vivo interaction between the bone and implants.

Adsorption↗

PubMedDate not supplied

Left anterior subregion of orbitofrontal cortex volume reduction and impaired organizational strategies in obsessive-compulsive disorder.

The orbitofrontal cortex (OFC) may be involved in the clinical and cognitive expressions of obsessive-compulsive disorder (OCD) and is a heterogenous region with respect to its cytoarchitecture, function and connectivity. This study was designed to examine the morphological abnormality of the anterior subregion of OFC and its relationship to clinical symptoms and cognitive performance in patients with OCD. We divided the OFC into anterior and posterior subregions using an external landmark and measured the gray matter volumes of each by three-dimensional magnetic resonance imaging in age- and sex-matched groups, which consisted of 34 OCD and 34 normal volunteers. Clinical and cognitive evaluations were completed using Yale-Brown Obsessive Compulsive Scale (YBOCS) and four sets of neuropsychological tests that assessed executive functions and visual memory. Volume reduction of the left anterior OFC was observed in patients with OCD versus normal controls. Also, a significant positive correlation was found between left anterior OFC gray matter volume and the copy score of the Rey-Osterrieth Complex Figure Test in patients with OCD. These results suggest that left anterior subregion volume reduction of the OFC may be related to impaired organizational strategies in patients with OCD.

Adult↗

PubMedDate not supplied

A new Leptographium species associated with the northern spruce engraver, Ips perturbatus, in western Canada.

An undescribed Leptographium species was isolated from the spruce-infesting bark beetle Ips perturbatus collected from felled spruce trees and logs in northern British Columbia and Yukon Territory. Morphologically, this fungus is similar to L. abietinum and L. hughesii but differed in a number of characteristics (e.g. the arrangement of its conidiophores). The fungus grew optimally at 25 C on 2% malt-extract agar and showed a high level of tolerance to cycloheximide. Comparison of rDNA and beta-tubulin gene sequences also confirmed that this Leptographium species represents an undescribed taxon. Thus we described it as a new species, Leptographium fruticetum sp. nov.

Antifungal Agents↗