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Biomedical subjects

Mitsuru Kawamura

Publications and source records attributed to Mitsuru Kawamura.

At least 19 recordsLinked to original sources
PubMed2007

[Neural mechanisms for object and color recognition].

We reported double-dissociation between the visual processing of the edges and the surfaces of objects. Patients with lateral occipital damage showed selective impairment in the perception of edges whereas those with medial ventral occipital damage showed selective impairment in the perception of the 3D structure of the surface. Patients with medial ventral occipital damage also exhibited impaired perception of color, which is also a surface property. Those results were consistent with those from neuroimaging studies. Taken together, those studies suggest that objects may be processed in two separate pathways in the ventral occipital cortex: the edges of objects are processed in the lateral pathway and the surface of objects are processed in the medial pathway. Both edges and surfaces play important roles in object recognition, and both types of perception should be evaluated in patients with visual agnosia.

Cerebral Infarction↗
PubMed2007

[Parallel processing of motion vision].

Several neuropsychological studies have reported dissociation between motion vision and object vision. One patient with motion blindness had a bilateral MT/V5 lesion and could see objects, but could not see the motion of the objects (Zihl et al, 1983). By contrast, some blindsight patients with primary visual cortex lesions cannot see objects but can see their movement (e.g. Riddoch, 1917). These results imply that movement vision and form vision rely on independent mechanisms. However one patient with motion blindness had controversial symptoms concerning motion vision. She could not perceive the movement of objects, although she could walk without colliding with obstacles and could catch incoming objects. It has also been reported that patients with a bilateral parietal lesion had well-preserved primary motion vision, but had problems walking and catching a ball (Vaina, 1998). Therefore, motion for vision and motion for action might have independent mechanisms. Such dissociation has also been noted in patients with Bálint syndrome. Some patients behave like a blind person but can walk and catch a ball, while other patients bump into obstacles while walking. These results indicate that the neural bases of motion vision are distinct from those of form vision and that there are subdivisions of motion vision.

Agnosia↗
PubMed2006

Impairment of odor recognition in Parkinson's disease caused by weak activations of the orbitofrontal cortex.

Olfactory dysfunction and abnormalities of olfactory brain structures are found in patients with Parkinson's disease (PD), and a number of studies have reported that olfactory dysfunction is caused by abnormalities of the central olfactory systems. We previously analyzed electroencephalograms (EEGs) and respiration simultaneously in normal subjects while testing for detection and recognition of odors. We identified changes in respiration pattern in response to odor stimuli and found inspiratory phase-locked alpha oscillations (I-alpha). The genesis of I-alpha were identified in olfactory-related areas including the entorhinal cortex, hippocampus, amygdale and orbitofrontal cortex with an EEG dipole tracing method. In the present study, we used the same protocol in PD patients and compared results of PD with those of age-matched controls. All PD patients detected odor, but 5 out of 10 showed impaired odor recognition. Changes in breathing pattern associated with emotional changes during exposure to odor stimuli were not observed in PD patients. I-alpha waveforms were not observed; however, positive waves followed by negative waves were identified approximately 100ms after inspiration onset. Dipoles of this component were localized in the entorhinal cortex for odor detection in all patients and in the entorhinal cortex and middle temporal gyrus for PD patients who could discriminate odors. Odor recognition in PD could be subserved by a different neural circuit from that of normal subjects, done through the temporal association cortex as a subsystem for recognizing the odor; however, the system may not be associated with the odor-induced emotions.

Aged↗
PubMed2006

Learning-related changes of brain activation in the visual ventral stream: an fMRI study of mirror reading skill.

A previous neuroimaging study has indicated that the visual dorsal stream may contribute to accurate reading of mirror-reversed words. However, the role of the visual ventral stream in the learning of mirror reading skill remains ambiguous. In the present fMRI study, we investigated learning-related changes in brain activation in the visual ventral stream in a mirror reading task. Subjects participated in three successive runs of the mirror reading task, in each of which they were asked to read mirror-reversed words and normal words as accurately and as quickly as possible. The behavioral data for the mirror reading condition showed significant improvement in reaction time but not in performance accuracy across the three runs. The activation data showed different learning-associated patterns related to the right and left visual ventral streams. On the right side, activity related to the reading of mirror stimuli was significantly greater than that related to normal stimuli in the first run only, whereas on the left side it was greater in all runs. Additional correlation analysis between response time data and percentage signal changes only in the mirror reading condition showed significant correlation on the right visual ventral stream in the first run only, whereas that on the left visual ventral stream was found only in the third run. The dissociable response between the right and left visual ventral streams may reflect learning-related changes in reading strategy and may be critical in improving the speed of reading mirror-reversed words.

Adult↗
PubMed2006

Decline or improvement? Age-related differences in facial expression recognition.

We examined age-related differences in facial expression recognition in association with potentially interfering variables such as general cognitive ability (verbal and visuospatial abilities), face recognition ability, and the experiences of positive and negative emotions. Participants comprised 34 older (aged 62-81 years) and 34 younger (aged 18-25 years) healthy Japanese adults. The results showed not only age-related decline in sadness recognition but also age-related improvement in disgust recognition. Among other variables, visuospatial ability was moderately related to facial expression recognition in general, and the experience of negative emotions was related to sadness recognition. Consequently, age-related decline in sadness recognition was statistically explained by age-related decrease in the experience of negative emotions. On the other hand, age-related improvement in disgust recognition was not explained by the interfering variables, and it reflected a higher tendency in the younger participants to mistake disgust for anger. Possible mechanisms are discussed in terms of neurobiological and socio-environmental factors.

Adolescent↗
PubMed2006

Simultaneous determination of selegiline and desmethylselegiline in human body fluids by headspace solid-phase microextraction and gas chromatography-mass spectrometry.

A method for the simultaneous determination of selegiline and its metabolite, desmethylselegiline, in human whole blood and urine is presented. The method, which combines a fiber-based headspace solid-phase microextraction (SPME) technique with gas chromatography-mass spectrometry (GC-MS), required optimization of various parameters (e.g., salt additives, extraction temperatures, extraction times and the extraction properties of the SPME fiber coatings). Pargyline was used as the internal standard. Extraction efficiencies for both selegiline and desmethylselegiline were 2.0-3.4% for whole blood, and 8.0-13.2% for urine. The regression equations for selegiline and desmethylselegiline extracted from whole blood were linear (r(2)=0.996 and 0.995) within the concentration ranges 0.1-10 and 0.2-20 ng/ml, respectively. For urine, the regression equations for selegiline and desmethylselegiline were linear (r(2)=0.999 and 0.998) within the concentration ranges 0.05-5.0 and 0.1-10 ng/ml, respectively. The limit of detection for selegiline and desmethylselegiline was 0.01-0.05 ng/ml for both samples. The lower and upper limits of quantification for each compound were 0.05-0.2 and 5-20 ng/ml, respectively. Intra- and inter-day coefficients of variation for selegiline and desmethylselegiline in both samples were not greater than 8.7 and 11.7%, respectively. The determination of selegiline and desmethylselegiline concentrations in Parkinson's disease patients undergoing continuous selegiline treatment is presented and is shown to validate the present methodology.

Amphetamines↗
PubMed2006

Impaired decision-making in Parkinson's disease.

The present study demonstrated that individuals with Parkinson's disease display impairments in making profitable decisions, as evidenced by poorer performance on the Iowa Gambling Task relative to matched controls. The ability to make beneficial judgments solely correlates with ability to appropriately attribute internal mental-state to other people, as shown in a mind-reading task. However, decision-making ability for individuals with Parkinson's disease is not associated with effective execution, intellectual function or depressed mood. These findings offer a new perspective on the cognitive impairments that affect social living and adaptive decisions for individuals with Parkinson's disease.

Affect↗
PubMed2006

Evaluation of cerebral dyschromatopsia using color afterimage.

Cerebral dyschromatopsia is traditionally evaluated by color discrimination tests such as the Farnsworth-Maunsell 100 Hue Test. These tests are also used to evaluate color-perception deficits caused by eye disease, and they do not tell us whether color perception is impaired in the eye or in the brain. Here, we used color afterimage to isolate color-perception deficits in the brain from those in the eyes, in a patient with cerebral dyschromatopsia. The results showed that the patient perceived color afterimage of yellow and blue with abnormal duration and chromaticity. On the other hand, the patient performed normally on the Farnsworth-Maunsell 100 Hue Test. We conclude that the color afterimage test would be useful to evaluate color perception in the brain.

Color Perception↗
PubMed2006

Disgust-specific impairment of facial expression recognition in Parkinson's disease.

There is contradictory evidence regarding whether the impairments of the recognition of emotional facial expressions in Parkinson's disease are specific to certain emotions such as disgust and fear. Generally, neurological case reports on emotion-specific impairments have been suspected of being confounded with the factor of task difficulty. Using a refined assessment method in which the difficulty factors were controlled by means of mixed facial expressions and item response theory, we attempted to clarify whether Parkinson's disease disproportionately impaired the recognition of specific emotions. We studied 14 patients with Parkinson's disease and 39 healthy controls who were matched in terms of gender, age, years of education and intelligence quotient. Whereas the refined method revealed that the patients with Parkinson's disease displayed significantly lower scores in disgust recognition alone, conventional methods failed to detect this impairment. In addition, control measures including face recognition abilities did not statistically explain the impairment observed in the patients. The results indicate that Parkinson's disease can indeed selectively impair the recognition of facial expressions of disgust; this provides concrete evidence for emotion-specific impairments that sufficiently withstands criticisms regarding the difficulty artefacts. Furthermore, the results support the proposed role of the basal ganglia-insula system in disgust recognition. This study effectively demonstrates the benefits of refining neuropsychological assessment by taking advantage of the modern psychometric theory.

Aged↗
PubMed2006

Disappearance of memory fragments in patients with Alzheimer's disease: evidence from a longitudinal study of visual priming.

Previous studies suggested that perceptual memory as indexed by visual priming is normal in patients with Alzheimer's disease (AD). However, these studies did not specifically test the long-term effects of visual priming, which may differ significantly between Alzheimer's patients and normal subjects. To test this possibility, we examined long-term visual priming in AD patients, 1 hour, 1 month, and 3 months after training. Our results indicated a significant difference in visual priming between AD patients and normal subjects after 3 months, but not 1 month. For AD patients, there was a strong positive correlation between the 3-month priming effect and the Mini-Mental State Examination (MMSE) scores-severely demented patients were less likely to exhibit priming after 3 months. It appears that severe cortical degeneration may render AD patients unable to consolidate their perceptual memories. Our results suggest that lack of visual priming in AD patients is linked to the inability to maintain fragmented perceptual memories.

Aged↗
PubMed2006

Right unilateral jargonagraphia as a symptom of callosal disconnection.

We report the case of a right-handed patient who exhibited right unilateral jargonagraphia after a traumatic callosal hemorrhage. The lesions involved the entire corpus callosum, except for the lower part of the genu and the splenium. The patient's right unilateral jargonagraphia was characterized by neologisms and perseveration in kanji and kana, and was more prominent in kana than kanji. The jargonagraphia was similar to that observed in crossed aphasia, except that agraphia occurred only with the right hand. The patient also showed right unilateral tactile anomia and right tactile alexia, along with right-ear extinction on a dichotic listening test for verbal stimuli, which suggested that language function was lateralized to the right hemisphere. Since this patient had learned to write with his right hand, kinesthetic images of characters were thought to be formed and stored dominantly in the left hemisphere. We suggest that the callosal lesions disturbed the interhemispheric transfer of information for the dual-route procedures for writing in the right hemisphere, allowing the kinesthetic images of characters stored in the left hemisphere to be processed freely, resulting in the right unilateral jargonagraphia. At least two factors seem to explain that kana was more defective than kanji. First, writing in kana, which is assumed to be processed mainly via a sub-word phoneme to grapheme conversion route, might depend more strongly on lateralized linguistic processing than writing in kanji. Second, kanji, which represent meaning as well as phonology, with much more complicated graphic patterns than kana, are assumed to be processed in both hemispheres.

Accidents, Traffic↗
PubMed2006

A disconnection syndrome due to agenesis of the corpus callosum: disturbance of unilateral synchronization.

Recently, interhemispheric disconnection syndromes have been noted in patients with agenesis of the corpus callosum (ACC) during the performance of certain tasks. However, few studies have demonstrated an asymmetric disconnection syndrome. In this report, we present just such a syndrome in a patient with ACC, who manifested ambidexterity (but with a left-hand tendency) and had high intelligence, no neurological deficits, and no associated malformations. In a comparison with similar subjects (amateur musician), we studied her asymmetric deficits using four tasks: (1) simple reaction time for visual stimuli, (2) paced finger tapping in synchrony with visual or auditory stimuli, (3) paced finger tapping without an external reference, and (4) rhythmical finger tapping in synchrony with visual or auditory stimuli. While the comparable subjects displayed no significant difference between hands, and the patient showed no significant difference between hands in the auditory paradigm, her tapping performance deteriorated significantly when asked to synchronize the left hand with timed visual stimuli, irrespective of whether finger tapping was paced or rhythmical. We believe that this phenomenon constitutes a novel asymmetrical disconnection syndrome in an ACC subject; these results suggest that synchronization of multimodal temporal information was lateralized in the left hemisphere (in this case), which is something that the ACC patient could not compensate for.

Adult↗
PubMed2006

Severe cortical involvement in MV2 Creutzfeldt-Jakob disease: an autopsy case report.

MV2 type sporadic Creutzfeldt-Jakob disease (sCJD) is reported to have a long duration and marked involvement of the cerebral deep gray matter. We describe an autopsied long-surviving sCJD case of MV2. In the early stages, the patient exhibited memory impairment, attention deficit and semantic memory disorder. Diffusion-weighted MRI showed abnormal hyperintensity signals along the cerebral cortex, sparing the thalami and basal ganglia. Pathological observations included: severe spongiosis throughout the cerebral cortex, several kuru plaques and plaque-like PrP deposits in the cerebellum, with only minimal degeneration in the thalami and basal ganglia. Our case suggests that MV2 has a wide clinicopathological spectrum, which ranges from "VV2" to "MM2" type.

Aged↗
PubMed2006

An autopsy case of frontotemporal dementia with severe dysarthria and motor neuron disease showing numerous basophilic inclusions.

We report a clinicopathological study of a patient suffering from frontotemporal dementia (FLD) with severe dysarthria and concomitant motor neuron disease (MND). The patient was a 52-year-old woman with almost simultaneous emergence of severe dysarthria and FTD. The severe dysarthria subsequently evolved into anterior opercular syndrome. Motor neuron signs then emerged, and the patient developed akinetic mutism approximately 2 years after the onset of the disease. The patient died of pneumonia after a 7-year clinical illness. Pathologically, severe and widespread degeneration in the frontal and temporal lobes, including the anterior opercular area, limbic system, basal ganglia, spinal cord and cerebellum, and frequent ubiquitin- and tau-negative basophilic inclusions were observed. The pyramidal tracts and anterior horns of the cervical cord also showed marked degeneration. Cases showing basophilic inclusions reported so far have been divided into two groups: early onset FTD and MND with basophilic inclusions. Our case presented clinicopathological features of both FTD and MND, which suggests that cases showing basophilic inclusions may constitute a clinicopathological entity of FTD/MND.

Autopsy↗
PubMed2006

A case of frontotemporal lobar degeneration with progressive dysarthria.

We investigated the evolution of the neurological and neuropsychological characteristics in a right-handed woman who was 53-years-old at the onset and who showed personality changes and behavioral disorders accompanied by progressive dysarthria. She had hypernasality and a slow rate of speech with distorted consonants and vowels, which progressed as motor disturbances affecting her speech apparatus increased; finally, she became mute two years post onset. Her dysarthria due to bilateral voluntary facio-velo-linguo-pharyngeal paralysis accompanied with automatic-voluntary dissociation fit the description of anterior opercular syndrome. She showed personality changes and behavioral abnormalities from the initial stage of the disease, as is generally observed in frontotemporal degeneration (FTD), and her magnetic resonance image showed progressive atrophy in the frontotemporal lobes; thus, she was clinically diagnosed with FTLD. This patient's symptoms suggest that FTLD, including bilateral anterior operculum degeneration, causes progressive pseudobulbar paretic dysarthria accompanied by clinical symptoms of FTD, which raises the possibility of a new clinical subtype in the FTLD spectrum.

Atrophy↗
PubMed2006

[Parkinsonism secondary to chronic subdural hematoma. A case report].

We described a case of secondary parkinsonism due to chronic subdural hematoma (CSH). An 83-year-old man developed memory impairment and gait disturbance gradually since one year ago, and these symptoms subacutely deteriorated after he fell down and hit his head. On admission he had moderate cognitive impairment, gait disturbance (wide-based, small steps and initial freezing), postual instability, akinesia and right-sided rigidity. He did not have resting tremor. A CT scan showed a right-sided CSH with marked compression on the left hemisphere, and remarkable decrease of the blood flow in the left cerebral hemisphere was revealed by single photon emission computed tomography. His neurological condition improved gradually through the decrease of the CSH, which suggested the diagnosis of secondary parkinsonism due to CSH. We thought that the CSH in the right hemisphere caused right-sided parkinsonism through mechanical compression to the left hemisphere, which was shown in the SPECT image, in this case. Elderly people suffering from subacute progressive parkinsonism, should undergo CT studies be to differentiate the parkinsonism secondary to CSH.

Aged, 80 and over↗
PubMed2005

Argyrophilic grain disease presenting with frontotemporal dementia: a neuropsychological and pathological study of an autopsied case with presenile onset.

A right-handed Japanese man with no consanguinity exhibited personality changes, speech disorder and abnormal behaviors, such as stereotypical, running-away, environment-dependent, and going-my-way behaviors, since the age of 49 years. At age 52 years, neuropsychological examination revealed frontal lobe dysfunctions, mild memory impairment, and transcortical sensory aphasia. MRI showed symmetrical severe atrophy of the anterior part of the temporal and frontal lobes. The clinical diagnosis was FTD. He died at age 54 years after a clinical illness of approximately 5 years. Numerous argyrophilic grains were observed throughout the limbic system, temporal lobe, frontal lobe and brainstem. In addition, there were many tau-positive neurons and glial cells. These findings are all compatible with argyrophilic grain disease (AGD). Our case, however, is atypical AGD because of the young age of onset of the disease and sharply circumscribed cortical atrophy exhibiting severe neuronal loss and gliosis. Our case, together with some other similar cases of atypical AGD, gives rise to the possibility that this type of AGD would constitute a part of pathological background of FTD.

Adult↗