Biomedical subjects

S Ishiai

Publications and source records attributed to S Ishiai.

At least 19 recordsLinked to original sources

PubMed2001

Significance of paradoxical leftward error of line bisection in left unilateral spatial neglect.

We intended to determine if leftward error of line bisection means "right" or "left" neglect in a patient with left unilateral spatial neglect. The patient placed the subjective midpoint to the left of the true center when bisecting lines without cueing. By contrast, when cued to the left endpoint, he showed typical rightward errors that became greater as longer lines were presented. Cueing to the right endpoint increased leftward errors compared with the bisections without cueing. The results suggest that paradoxical leftward error of line bisection is a form of "left" unilateral spatial neglect in that the shortness of the left extent is ignored.

Cues↗

PubMed2001

Conflict and integration of spatial attention between disconnected hemispheres.

OBJECTIVES: To clarify how the disconnected hemispheres perceive a line and bisect it with successful or unsuccessful integration of spatial attention. METHODS: Eye movements were recorded when a patient with an extensive callosa infarction bisected horizontal lines. The lesion extended into the left cingulate gyrus. RESULTS: When the patient bisected lines with the right hand, the gaze was initially directed rightward and shifted further to the right side with the execution of manual response, which resulted in rightward errors. Shortly after bisection, rapid ocular searches occurred to the left side, whereas the rightward errors did not decrease throughout the trials. When using the left hand, there was no deviation of the gaze before presentation of lines. In the first few trials, the patient bisected the line with a leftward error and then searched rapidly to the right side. The subsequent bisections were almost accurate, as the subjective midpoint was placed near the point of the initial fixation that fell around the true centre. Ocular searching was mostly absent during and after line bisection. CONCLUSIONS: In callosa disconnection, left unilateral spatial neglect may appear when use of the right hand induces a rightward bias in the attentional control of the left hemisphere and damage to its cingulate gyrus inhibits interhemispheric integration of attention. Resultant rightward errors of line bisection often cause interhemispheric conflict of attention, as the right hemisphere perceives the longer extent on the left side. By contrast, the disconnected but intact right hemisphere may bisect a line accurately by integrating attention to the extents perceived in the left and right visual fields.

Attention↗

PubMed2001

[Lateralization and interhemispheric integration of directed attention].

Directed attention is a function to direct and shift the focus of awareness adequately to behaviorally relevant sensory events. Healthy subjects direct attention evenly to right and left hemispaces. Unilateral spatial neglect is a failure to respond normally to stimuli on the side opposite a cerebral lesion, which is considered to represent a unilateral disruption of directed attention. The established clinical observation that neglect usually occurs after right hemisphere lesions and the results of functional imaging studies suggest the right hemisphere dominance for directed attention. It is hypothesized that the right hemisphere distributes attention to space bilaterally, whereas the left hemisphere distributes attention primarily to right hemispace. However, patients with callosotomy show no apparent neglect with either right or left hand. Ishiai et al. (2001) reported detailed analyses of eye movements when a patient with a callosal infarction bisected lines. Left unilateral spatial neglect may appear, when use of the right hand induces a rightward bias in the attentional control of the left hemisphere and damage to its cingulate gyrus inhibits interhemispheric integration of attention. By contrast, the disconnected but intact right hemisphere may bisect a line accurately by integrating attention to the extents perceived in the left and right visual fields.

Attention↗

PubMed2000

Unilateral spatial neglect in AD: significance of line bisection performance.

BACKGROUND: Unilateral spatial neglect has been rarely reported in patients with AD, although they often have right and left asymmetry of temporoparietal dysfunction. OBJECTIVE: To investigate if patients with AD would show unilateral spatial neglect in the line bisection test, and to reveal the relationship between their neglect and the area of cerebral dysfunction. METHOD: Thirty-two patients with mild to moderate AD and 32 age-matched healthy control subjects underwent an extensive line bisection test. SPECT was also obtained for the patients. RESULTS: Rightward bisection errors exceeded the normal range in 25% of patients with AD. They exhibited greater rightward errors for the longer lines in the left hemispace than in the right hemispace, and with the right hand than with the left hand; this corresponds to the characteristics of neglect seen after right hemisphere lesions. All patients who bisected 200 mm lines with errors over 10 mm showed disproportionate lowering of performance IQ and asymmetric right hemisphere hypoperfusion, especially in the temporoparietal region. Seventy-five percent of the patients performed normally in the center presentation but erred slightly toward the body midline in the right and left hemispaces. CONCLUSION: Left unilateral spatial neglect in mild to moderate AD may be rather common if tested with the line bisection test. Rightward errors over 10 mm suggest right temporoparietal dysfunction. In AD, three or more bisections of 200 mm lines in the center presentation are recommended for detection of neglect. Patients with AD but without neglect may have difficulty in shifting attention into the peripheral sector of the egocentric space.

Aged↗

PubMed2000

Why are some patients with severe neglect able to copy a cube? The significance of verbal intelligence.

Cube-copying is often used to assess constructional ability of brain-damaged patients and the influence of unilateral spatial neglect is often pointed out in patients with right hemisphere lesions. However, some patients with severe neglect perform cube-copying satisfactorily. The aim of the present study is to identify the factors that affect the performance of cube-copying in patients with left unilateral spatial neglect. Constructional performance was investigated in 100 patients with unilateral spatial neglect using a task to copy the Necker cube. The relationship of the patients' cube-copying performance to the severity of their neglect, as well as other factors (verbal intelligence, age, duration after onset of the disease, educational level, lesion site, piecemeal approach, and side of starting to copy) was analyzed. Twenty-two normal subjects also participated in this study as controls. Among many factors adopted for analysis, neglect severity and verbal intelligence were found to be primary factors affecting the cube-copying performance of the patients with unilateral spatial neglect. The effect of neglect severity on cube-copying performance was apparent in the patients whose verbal intelligence was deteriorated, but was not observed in the patients with preserved verbal intelligence. Similarly, the effect of verbal intelligence on cube-copying performance was apparent in the patients with severe neglect, but not in the patients with mild neglect. We conclude that constructional ability in the copying of a cube is determined by verbal intelligence, as well as by the severity of unilateral spatial neglect.

Aged↗

PubMed2000

Line versus representational bisections in unilateral spatial neglect.

OBJECTIVES: To clarify the mechanisms of left unilateral spatial neglect found in the bisection of lines after cueing to the left end point and to determine whether neglect occurs for the mental representation of a line. METHODS: A new representational bisection task was developed to eliminate the influence of the right segment of the physical line that would attract attention. Eight patients with typical left unilateral spatial neglect underwent line and representational bisection tasks on a computer display with a touch panel. In the line bisection with cueing, they bisected a line after touching the left end point. In the representational bisection, the patients were presented with a line until they touched the left end point. On the blank display, they pointed to the subjective midpoint of the erased line. The performances of the two bisection tasks were compared when the length and position of stimulus lines were varied. RESULTS: The rightward errors in the representational bisection were greater than or equivalent to those in the line bisection with cueing. The effect of line length in which the errors became greater for the longer lines was equally found in the line bisection with cueing and the representational bisection. This was confirmed in the condition where the right end point was placed at a fixed position and the line length was varied. CONCLUSIONS: After cueing to the left end point, rightward bisection errors of patients with neglect are not caused by overattention to the right segment of the physical line. Left neglect occurs mainly for the mental representation formed at the time of cueing or seeing the whole extent of a line.

Aged↗

PubMed1999

Unassociated responses to two related task demands: a negative factor for improvement of unilateral spatial neglect.

Patients with relatively mild unilateral spatial neglect underwent the line bisection task with self-estimation, where they were asked two different questions about the relationship of their subjective midpoint to the line. For the first trial, all patients responded by "yes" when asked whether their subjective midpoint was placed at the center of the line, but by "left" or "right" when asked to indicate the longer segment of the bisected line. In the subsequent trials, they repeatedly reported that their subjective midpoints were placed at the true center, even after they had recognized their bisection errors when indicating the longer segment. Of the 32 patients, 28 kept on showing this pattern of responses in almost all the 30 trials. Moreover, the patients who could estimate the longer segment showed no improvement of line bisection throughout the trials. Their performances strongly depended upon the task demand regarding the subjective midpoint. These results demonstrate that the patients treated the two related tasks as independent. Accordingly, they could not improve their performances on one task with the feedback from their performances on the other. The lack of association between the responses to two related task demands may be one of the factors that prevent patients with unilateral spatial neglect from improving the deficit.

Aged↗

PubMed1998

Effects of unilateral spatial neglect on spatial agraphia of kana and kanji letters.

Left unilateral spatial neglect (USN) and spatial agraphia are both caused by right hemisphere damage. However, effects of USN on spatial agraphia have not been fully investigated. This study examined performances of patients with or without neglect and normals on single letter writing, using Japanese unique writing systems, kana (phonogram) and kanji (ideogram). Our patients exhibited agraphia of kanji, but not of kana. However, accuracy of writing was not associated to neglect severity, and errors for writing to dictation occurred either on the left or right side of kanji. Right frontal damage seemed to be related to the genesis of duplication or omission errors of repeated elements. Effect of USN was limited to spatial arrangement of letters and copying performance.

Aged↗

PubMed1998

What is line bisection in unilateral spatial neglect? Analysis of perceptual and motor aspects in line bisection tasks.

Three patients with unilateral spatial neglect could detect the difference of length between the right and left segments when a line had a transection mark. To examine the effect of response mode, the manual line bisection task and a new "line bisection task by fixation" were given to the patients. In tasks that used lines with no landmark, they showed apparent rightward errors. The results suggest that line bisection is not a task that examines the ability of patients with neglect to compare the right and left extents of a line. Where to fixate as the subjective midpoint may determine the rightward errors of bisection, whether manual response is used or not.

Aged↗

PubMed1998

[Slowly progressive aphemia--a case report].

A 69-year-old women was admitted to Tokyo Medical and Dental University Hospital because of slowly progressive difficulty in speech production over 8-years. On admission, her spontaneous speech was non-fluent, limited to one-syllable utterance, and severely efforty. But her visual and auditory comprehension was preserved. There was no significant general intellectual deterioration. Severe buccofacial apraxia, but no swallowing was observed. So we considered her difficulty in speech as aphemia. Three-dimensionally reconstructed surface MR image clearly showed severe atrophy in the posterior part of the left inferior frontal gyrus and the lower part of the left pre-central gyrus. The FDG-PET demonstrated a focal hypometabolism in the same region. The lesion in this area was suggested to be a cause of speech production difficulty in this case.

Aged↗

PubMed1997

Distinct processes in line bisection according to severity of left unilateral spatial neglect.

We investigated the line bisection performances in 24 patients with left unilateral spatial neglect. They bisected lines of two lengths in three positions relative to the sagittal midplane of the body. The results showed that in the mild or moderate neglect patients, length and spatial locations of the lines affected the placement of the subjective midpoint. In the severe neglect patients, however, length had little effect on their performances, and location of the right endpoint in the egocentric space mainly determined the subjective midpoint. The line bisection process of the severe neglect patients was not only quantitatively but also qualitatively different from that of the mild or moderate cases.

Adult↗

PubMed1997

Dissociated neglect for objective and subjective sizes.

We examined the effect of line length and viewing distance on the line bisection performance in near space in five patients with left unilateral spatial neglect following right parietal lesions. A line bisection task by fixation was devised to avoid the influence of manual responses. The rightward deviation measured in visual angle increased linearly as a function of the visual angle of lines 150 mm or more long. This linearity, however, did not hold for lines of 100 mm or less. The deviation measured in length was nearly constant for each of these short lengths, even when the visual angle was varied at different viewing distances. The patients therefore discriminated the objective lengths of the short lines. For small objects, neglect patients may distribute attention mainly on the coordinates scaled for objective size.

Aged↗

PubMed1997

Disappearance of unilateral spatial neglect following a simple instruction.

OBJECTIVES: To clarify the reason why patients with left unilateral spatial neglect fail to copy the left side of a daisy like flower, not continuing to draw petals all around. METHODS: A flower was simplified and a figure was made that consisted of a large central circle and small circles surrounding it. Four patients with typical left unilateral spatial neglect performed copying and arrangement tasks to make this figure. In the arrangement task, they were instructed to arrange small circles all around the printed central circle. RESULTS: The patients' identification of the composition seemed flawless. In the copying task, they showed neglect, leaving a space on the left side. They seemed to adhere to their plan to place the same number of small circles as those of the model figure. By contrast, neglect disappeared in the arrangement task. CONCLUSION: Patients with neglect can draw the figure satisfactorily if they use a spatial strategy to arrange small circles all around. This strategy seems to improve motivation for drawing and awareness for the left space. It is considered that in the copying of figures such as a daisy, failure to use a spatial strategy plays an important part in the appearance of left unilateral spatial neglect.

Aged↗

PubMed1997

[Thymic carcinoid: a case report of complete surgical resection using internal mammary artery (IMA) retractor].

Carcinoid tumor of the thymus is a rare tumor and discovered not infrequently at advanced stage. A 56-year-old male was admitted to our hospital with severe chest pain. Chest X-ray film and CT scan, revealed a tumor mass in the anterior mediastinum. The patient underwent extended thymectomy including tumor completely through median sternotomy in combination with partial resection of pericardium, mediastinal pleura and left upper lobectomy using internal mammary artery (IMA) retractor. The microscopic findings of the tumor revealed carcinoid Invasion to pericardium and lung was found microscopically. After the operation he has been treated by radiotherapy and any regrowth of the tumor has never been detected for 32 months. This case who had been undergone complete resection using IMA retractor followed by radiotherapy seemed to have better prognosis. Accordingly, extended thymectomy including tumor should be carried out for thymic carcinoid, and the IMA retractor is useful for complete surgical resection through median sternotomy.

Carcinoid Tumor↗

PubMed1997

[Neuropsychological disorders in minor hemisphere damage].

Damage to the minor hemisphere or the right hemisphere of most right-handed subjects produces various neuropsychological disorders. Unilateral spatial neglect is the deficit to respond or orient to stimuli on the left side. The inferior parietal lobule is most frequently involved in the lesions of neglect patients, but lesions confined to the lobule may not cause chronic neglect. Severe and lasting neglect is frequently found in patients with an infarction in the territory of the middle cerebral artery or the anterior choroidal artery. Neglect is usually mild or moderate after frontal lesions. The most important mechanism of neglect seems to be disorders in spatial attention: rightward attentional bias, and impairment in disengagement and shift of attention from the right side. Directional hypokinesia is rarely observed in the chronic stage. Non-spatial factors, such as motivational deficit, insufficient compensation with verbal intelligence, or disuse of an appropriate spatial strategy may also contribute to the appearance of neglect. Anosognosia for hemiplegia is found in about half of patients with acute cerebrovascular accidents in the right hemisphere. Generalized attentional and intellectual deficits, diffuse brain atrophy or hypometabolism, and presence of multiple infarction may result in chronic anosognosia. Constructional disability is observed in about 30% patients with either hemisphere damage. Dressing apraxia is more frequent in right hemisphere damage. These two disorders, however, rarely appear as isolated neuropsychological deficits. Most patients show some of the accompanying disorders, such as unilateral spatial neglect, anosognosia, anosodiaphoria, and generalized attentional and intellectual impairment. By contrast, motor neglect may occur independently of the other disorders. Motor neglect follows damage to either hemisphere, although it occurs more frequently after right hemisphere damage. Neuropsychological deficits characteristic of right hemisphere damage may be unilateral spatial neglect in the acute and chronic stages and anosognosia for hemiplegia in the acute stage.

Apraxias↗

PubMed1996

Ineffective leftward search in line bisection and mechanisms of left unilateral spatial neglect.

We examined the eye-fixation pattern of a patient with severe left unilateral spatial neglect who showed leftward searches of various extent in more than half of line bisection trials. Because of complete left homonymous hemianopia, he perceived only the segment of the line between its right endpoint and the point of the leftmost fixation. In the trials with leftward searches, he frequently placed the subjective midpoint on the right part of the perceived segment. In the trials without leftward searches, he placed it near the left extreme point of the perceived segment. For all these bisections, the subjective midpoint was constantly placed far to the right of the true midpoint of the line irrespective of the length perceived. We consider that in severe left unilateral spatial neglect, rightward attentional bias is the predominant factor that determines where to place the subjective midpoint. Transient attentional shift to the left may produce leftward searches, but it does not induce effective processing of line bisection.

Aged↗

PubMed1996

Diverse patterns of performance in copying and severity of unilateral spatial neglect.

We analysed the performances of 69 patients with left unilateral spatial neglect in copying a multi-object figure, as well as their performance of the line cancellation and line bisection tests. Three patterns of copying were mainly observed. The first pattern was almost satisfactory performance in copying the central figure with occasional omission of the elements located more laterally to the left. The second pattern was omission of the left half of the whole figure, which was the pattern expected of patients with typical left unilateral spatial neglect. The third pattern was left unilateral spatial neglect when copying the central figure, with favourable copying of left lateral objects; this may be regarded as "object-centered" neglect. Performance of the line cancellation test, which requires exploratory ability, was significantly better for the patients with the third pattern than for those with the second pattern. A significant difference was also observed between the two groups of patients in performance of the line bisection test, in which exploratory ability plays a more minor role. No significant difference was found in performance of the line cancellation and line bisection tests between the patients with the third and first patterns, in spite of remarkable differences in their copying performances. No distinctive characteristics were found for any group of patients as regards lesion, age, duration after onset, education, and WAIS scores. Therefore we concluded that in most of our patients with neglect, these diverse patterns of copying deficits resulted from different levels of neglect severity but not from different types of unilateral spatial neglect.

Adult↗

PubMed1996

Appearance and disappearance of unilateral spatial neglect for an object: influence of attention-attracting peripheral stimuli.

We reported a dramatic phenomenon of appearance and disappearance of left unilateral spatial neglect for the same single object. In experiment 1, four patients with mild neglect who copied a single flower satisfactorily showed left neglect in copying of the same flower when it was accompanied with some peripheral stimuli. In experiment 2, we included three additional conditions to determine the stimulus component crucial for left neglect of the flower: a flower with a stem and a flower with either right or left peripheral stimuli were also used for copying. Overall results showed that neglect was most evident for the flower with the right peripheral stimuli. On the other hand, the presence of left stimuli provoked less severe neglect of the flower, which was as mild as that in the single flower condition. The results were explained in terms of an attentional mechanism underlying unilateral spatial neglect. When copying the flower with peripheral stimuli on both sides or on the right side, the stimuli on the right side might attract the patient's attention. Consequently, he exhibited left neglect on the central flower. On the other hand, neglect was less evident in the other conditions, since the figures did not include such attention-attracting stimuli on the right side.

Adult↗