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Juhee Chin

Publications and source records attributed to Juhee Chin.

8 recordsLinked to original sources
PubMed2005

The influence of illusory motion on line bisection performance in normal subjects.

The present study examines whether illusory movement (IM) of a horizontal line, induced by a moving background (MB), influences line-bisection performance in normal subjects. The first experiment attempted to identify the speeds of MB that induce IM. We found that when speed is increased from 1.53 degrees to 13.3 degrees/sec, IM increases, but that with further speed increases, IM decreases. Leftward MB induces rightward IM, and vice versa. In the second experiment, we had subjects bisect lines at MB speeds that had been shown to induce IM in the first experiment. We found that leftward MB induced a rightward bias, and vice versa. We also found that there was a relationship between the magnitude of IM and the degree of bias. In the third experiment, by making the target line larger than the MB, we made the conditions where IM was presumably absent. Unlike the results of bisection performed with IM, subjects showed a bias in the direction of the MB. Overall, these experiments demonstrated that the perception of motion induces subjects to attend in the direction of movement.

Adult↗
PubMed2004

Visual search pattern during the line quadrisection task in normal subjects.

A common test for the assessment of hemispatial neglect is the line bisection test. A recent modification of the task has been reported wherein subjects place a mark at either 25% or 75% of line length ('quadrisection'). In a previous study, we suggested that line quadrisection might entail iteration of two steps involved in standard line bisection: (1) finding the midpoint of the entire line, and then (2) bisecting the half-line segment between the adjudged midpoint and the line end ipsilateral to the target quadrisection point. The present study investigated eye movement patterns during line quadrisection in order to test this hypothesis. Twenty normal volunteers determined the left or right quadrisection point of a horizontal line while their eye movements were recorded using two-dimensional video-oculography. Analysis revealed that, like the results of previous studies on bisection, most normal subjects fixate the central portion of the line segment before reaching the target area during the quadrisection task. Normal subjects' eye movements during quadrisection performance share a number of features with line bisection and provide support for the two-step processing hypothesis.

Adult↗
PubMed2004

Mechanism of the closing-in phenomenon in a figure copying task in Alzheimer's disease patients.

The"closing-in phenomenon"in figure copying tasks refers to a tendency to copy near the target, or to overlap the target to be copied. The mechanisms underlying the closing-in phenomenon have not been fully elucidated. We posit that closing-in may be related to the patients'compensatory strategies to overcome visuospatial dysfunction or visuospatial working memory deficit. Thus, it is expected that as the complexity of the target figure or the distance from the target to the copying space is increased, the magnitude of closing-in will be increased. Thirteen patients with Alzheimer's disease (AD) who demonstrated closing-in on a screening test and 15 healthy controls participated in this study. Each subject copied figures in conditions that varied in terms of figure complexity and distance from the target to the copying space. Neither figure complexity nor distance between the target and copying space affected the degree of closing-in in normal subjects. In contrast, in AD patients, the magnitude of closing-in increased as a function of figure complexity; however closing-in was unchanged by varying the distance from the target to the copying space. Our results suggest that copying near the target figure might be the patients'strategy to compensate for their visuospatial dysfunction or visuospatial working memory deficits.

Aged↗
PubMed2004

Serial positron emission tomography findings in a patient with hydrocephalic dementia and Alzheimer's disease.

Comorbidity of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD) is not uncommon. However, few studies have reported the clinical courses of these patients in depth. A 73-year-old woman was confirmed to have AD by a biopsy performed during a shunt operation for NPH after a head trauma. She was followed for 4 years using serial neuropsychological tests and positron emission tomography (PET). Her clinical symptoms remained improved for 2.5 years and then declined. The 1-year minus the presurgical PET scan highlighted the bilateral frontal area, basal ganglia, and thalamus, which may reflect brain regions associated with the improvement of hydrocephalic dementia. On the other hand, the 1-year minus the 4-year scan highlighted the bilateral temporoparietal area and the posterior cingulate gyrus, which may reflect brain regions associated with the aggravation of AD. This subtraction method may be useful for monitoring the clinical course in patients with NPH and AD.

Aged↗
PubMed2002

Manual approach during hand gesture imitation.

BACKGROUND: Patients' tendency to draw near or into the target when copying figures, a phenomenon termed closing-in, has been previously described. That the closing-in could occur when copying hand gestures has also been noted. OBJECTIVES: To study a patient with corticobasal degeneration to quantify his manual approach behavior and to test a possible working memory hypothesis. METHODS: The subject of this study is a patient with severe ideomotor apraxia from probable corticobasal degeneration. Fluorine 18-labeled deoxyglucose-positron emission tomographic findings revealed a hypometabolism involving the bilateral parietotemporal and the right frontal lobes. When asked to copy an examiner's (J.C.K.) hand gesture, the patient approached, touched, or grasped the examiner's hand, a behavior mostly consistent with the closing-in behavior previously proposed. To investigate the frequency and severity of closing-in, the patient was asked to copy 20 meaningless hand gestures (10 simple and 10 complex). Copying the 20 hand gestures was performed with either the left or the right hand while the patient was seated opposite the examiner (across condition) or on the same side of the examiner (lateral condition). RESULTS: Of the 80 trials, closing-in occurred in 43 (53.8%) (35 with approaching, 6 with touching, and 2 with grasping). The closing-in was more frequent and more severe when gesturing with the left than the right hand, but it did not differ between the lateral and across conditions and between simple and complex gestures. CONCLUSIONS: Corticobasal degeneration might be associated with aberrant manual approach behavior. Although our results do not support the working memory hypothesis, frontal dysfunction might have led to a loss of voluntary control of ontologically primitive propensity to move the forelimb in the direction to which one attends.

Aged↗
PubMed2002

Hanja alexia with agraphia after left posterior inferior temporal lobe infarction: a case study.

Korean written language is composed of ideogram (Hanja) and phonogram (Hangul), as Japanese consists of Kanji (ideogram) and Kana (phonogram). Dissociation between ideogram and phonogram impairment after brain injury has been reported in Japanese, but few in Korean. We report a 64-yr-old right-handed man who showed alexia with agraphia in Hanja but preserved Hangul reading and writing after a left posterior inferior temporal lobe infarction. Interestingly, the patient was an expert in Hanja; he had been a Hanja calligrapher over 40 yr. However, when presented with 65 basic Chinese letters that are taught in elementary school, his responses were slow both in reading (6.3 sec/letter) and writing (8.8 sec/letter). The rate of correct response was 81.5% (53 out of 65 letters) both in reading and writing. The patient's performances were beyond mean-2SD of those of six age-, sex-, and education-matched controls who correctly read 64.7 out of 65 and wrote 62.5 out of 65 letters with a much shorter reaction time (1.3 sec/letter for reading and 4.0 sec/letter for writing). These findings support the notion that ideogram and phonogram can be mediated in different brain regions and Hanja alexia with agraphia in Korean patients can be associated with a left posterior inferior temporal lesion.

Cerebral Infarction↗
PubMed2002

Globus pallidus lesions associated with high mountain climbing.

Acute mountain sickness (AMS) occurs commonly in hikers who are rapidly exposed to high altitude environments. Despite the numerous reports of AMS, few studies have reported pallidal lesions associated with altitude sickness. A previously healthy 49-yr-old Korean patient, after ascent to 4,700 m, suffered symptoms consistent with AMS. After returning home, the patient showed changes in personality characterized by abulia, indifference, and indecisiveness. T2 weighted brain magnetic resonance imaging showed high signal lesions involving bilateral globus pallidus. Our case suggests that globus pallidus injury should be included in the differential diagnosis of patients with personality or cognitive change after recovery from AMS.

Altitude↗