Biomedical subjects

Y Ikejiri

Publications and source records attributed to Y Ikejiri.

At least 19 recordsLinked to original sources

PubMed2001

Transient global amnesia (TGA) in an MEG study.

A patient who had experienced an attack of transient global amnesia (TGA) was examined using neurophysiological methods. Magnetoencephalography (MEG) was performed and the Wechsler Memory Scale-Revised (WMS-R) test was administered at 5 days and at more than a month after the TGA episode. MEG data on neuronal activity obtained while the patient was undertaking a working memory task and during rest were analyzed using the wavelet-crosscorrelation method, which reveals time-lag and information flow between related sites in the brain. The WMS-R memory scores showed dramatic improvement when the test was administered a month following the attack, although no significant changes were observed in EEG, MRI and SPECT data. The MEG study revealed that under a working memory load how the neuron works functionally and the information propagates assembly within the right hemisphere, and that these brain functions were not performed adequately shortly after the TGA attack.

Amnesia, Transient Global↗

PubMed2001

Conflict of intentions due to callosal disconnection.

OBJECTIVES: Three patients with callosal syndrome manifested a peculiar symptom in that they were unable to perform intended whole body actions because another intention emerged in competition with the original one. Attempts were made to clarify the symptomatology of this manifestation and its possible mechanism is discussed. METHODS: The three patients are described and previous reports on patients with callosal damage were reviewed. Four additional patients with similar symptoms were found and the clinical features common to all seven patients were examined. RESULTS: This symptom could not be attributed to unilateral movement disorders such as unilateral apraxia, intermanual conflict, or compulsive manipulation of tools. The manifestations included marked hesitation in initiating actions, interruption of actions, repetitive actions, and performance of unintended actions with difficulty in correcting them. All patients, except one, had a lesion in the posterior half of the body of the corpus callosum, and there was no significant involvement of the cerebral cortex. The symptom became manifest later than 4 weeks after callosal damage. It occurred during spontaneous actions, but not during well automated actions nor when following instructions. CONCLUSION: This symptom, tentatively named "conflict of intentions", can be regarded as a fragment of diagonistic dyspraxia originally described by Akelaitis, although it can occur independently of intermanual conflict. Normally, the right and left cerebral hemispheres may be complementarily modifying automated whole body actions in order to adapt behaviour to changes of the environment as well as to the intention. Partial callosal disconnection without significant cortical involvement would exaggerate the disparity between the role of each hemisphere through the reorganisation of neural systems after callosal damage. Such double, often contrary, behavioural tendencies may sometimes simultaneously enter the patient's awareness.

Adult↗

PubMed2000

Theta rhythm increases in left superior temporal cortex during auditory hallucinations in schizophrenia: a case report.

Auditory hallucinations (AH), the perception of sounds and voices in the absence of external stimuli, remain a serious problem for a large subgroup of patients with schizophrenia. Functional imaging of brain activity associated with AH is difficult, since the target event is involuntary and its timing cannot be predicted. Prior efforts to image the patterns of cortical activity during AH have yielded conflicting results. In this study, MEG was used to directly image the brain electrophysiological events associated with AH in schizophrenia. We observed an increase in theta rhythm, as sporadic bursts, in the left superior temporal area during the AH states, whereas there was steady theta band activity in the resting state. The present finding suggests strong association of the left superior temporal cortex with the experience of AH in this patient. This is consistent with the hypothesis that AH arises from areas of auditory cortex subserving receptive language processing.

Adult↗

PubMed2000

Functional anatomical study of psychogenic amnesia.

Psychogenic amnesia is characterized by an inability to recall information already stored in the patient's memory. It is usually related to a stressful or traumatic event that cannot be explained by manifest brain damage. To examine the underlying functional disturbance of brain areas in this condition, we performed a positron emission tomography (PET) activation study on a psychogenic amnesic patient and on 12 normal control subjects. A task requiring explicit retrograde memory of faces was compared with a control task. To assess functional modifications associated with the processes of recovery, a second PET study was performed on the patient 12 months after onset. During the task, activation of the right anterior medial temporal region including the amygdala was increased in the psychogenic amnesic patient. Activation of the bilateral hippocampal regions increased only in the control subjects. During recovery, the right anterior medial temporal region became less active while the right hippocampal region became more active. Activation levels also differed in the anterior cingulate cortex, prefrontal cortex and some other cortical regions between control subjects and the patient. These findings suggest that the changes in these limbic and limbic-cortical functions are related to symptoms of the psychogenic amnesia.

Adult↗

PubMed2000

The neural basis of perceptual and conceptual word priming--a PET study.

Positron emission tomography scans were obtained in 13 normal subjects during perceptual and conceptual word priming tasks with the aim to investigate the neural system specific to the two priming conditions. In the prescan phase, subjects were primed perceptually or conceptually with two separate procedures, while in the scan phase, they performed the same stem completion task. Therefore we could compare the results of the two priming tasks in a direct manner. A fixation control task and a baseline task (completion of stems that did not correspond to previously seen words) were also given. A specific blood flow decrease was found in the left inferior temporal cortex in the perceptual word priming condition and in the left superior temporal / inferior parietal cortex in the conceptual word priming condition. Each blood flow change may reflect transient changes in the cortical areas subserving the processing of the perceptual and conceptual components of word priming.

Adult↗

PubMed1999

Different neural substrates for Kanji and Kana writing: a PET study.

To investigate the neural substrate underlying the mechanisms of Kanji and Kana writing, we conducted a PET activation study during mental writing task in eight right-handed normal Japanese subjects. During scans subjects were required to mentally write a Kanji or three Kana letters with their right hand, for each stimulant word presented auditorily. The direct comparisons between Kanji writing and Kana writing revealed that the left posterior inferior temporal gyrus was activated in Kanji writing while the left angular gyrus was activated in Kana writing. In addition, more extensive areas were activated in Kanji writing compared with Kana writing. These results suggest that different respective neural substrates are involved in Kanji and Kana writing respectively.

Adolescent↗

PubMed1999

A pedigree with a novel presenilin 1 mutation at a residue that is not conserved in presenilin 2.

OBJECTIVE: To disclose a novel mutation of the presenilin 1 (PS1) gene responsible for early-onset Alzheimer disease and to clarify genotype-phenotype correlation that should help to establish the function of this protein. BACKGROUND: The PS1 and presenilin 2 (PS2) genes carry missense mutations in families with Alzheimer disease. The PS1 and PS2 proteins have similar structures, and all presently known mutations are in nucleotides coding for amino acids that are conserved between the 2 presenilins. METHODS: Sequence and restriction fragment length polymorphism analyses of PS1 gene of DNA from a pedigree with early-onset Alzheimer disease. RESULTS: Sequence analysis disclosed a novel PS1 mutation in a pedigree of Japanese origin with early-onset Alzheimer disease. This mutation, which is predicted to cause a missense substitution of lysine for glutamic acid, occurred at codon 123 of PS1 that was not a conserved residue in PS2. The 2 patients of this pedigree shared an early clinical phenotype consisting of later-onset, progressive aphasia, but preserved visuospatial ability, which was indistinguishable from those of other PS1-associated Alzheimer disease cases. CONCLUSION: These results demonstrate that a missense mutation in a region not conserved between PS1 and PS2 can cause Alzheimer disease.

Age of Onset↗

PubMed1999

Molecular cloning of cDNAs of mouse peptidylarginine deiminase type I, type III and type IV, and the expression pattern of type I in mouse.

Peptidylarginine deiminases (PADs), a group of post-translational enzymes, catalyze the conversion of protein-bound arginine residues to citrulline residues in a calcium ion-dependent manner and are widely distributed in various organs of vertebrates. Although the existence of four isoforms of PAD (types I, II, III, and IV) is reported in rodents, the relative functions of the isoforms with respect to their colocation in the tissues have yet to be explored. In this study, we cloned the full-length cDNA encoding mouse PAD type I by screening a uterine cDNA library and using the RACE method. This cDNA consists of an open reading frame of 1989 bases encoding 662 amino acids (73,823 Da), a 5'-untranslated region of 127 bases and a 3'-untranslated region of 1639 bases. Comparative reverse transcription-PCR and Northern-blot analyses detected PAD type I mRNA only in the epidermis and uterus. Administration of estrogen to adult ovariectomized mice increased the content of PAD type I mRNA in the uterus, providing evidence that its expression is under the control of the sex steroid hormone. We also cloned the full-length cDNAs of mouse PAD type III and type IV by the reverse transcription-PCR and RACE methods. The primary structure of PAD type III contains 664 amino acids (75,098 Da) deduced from the coding region of 1995 bases, and the primary structure of PAD type IV consists of 666 amino acids (74,475 Da) deduced from the coding region of 2001 bases. Comparison of the deduced amino acid sequences of all four isoforms of PAD showed about 50% identity with each other, the 3' regions being highly homologous compared with the 5' regions.

Amino Acid Sequence↗

PubMed1999

Retrograde temporal order amnesia resulting from damage to the fornix.

Some amnesic patients show an impairment of temporal order memory that cannot be accounted for by content memory deficits. The performance of an amnesic patient on memory tasks assessing the patient's content and temporal memories for remotely acquired material is described, after a lesion including the bilateral anterior fornix and adjacent anterior thalamus. The patient displayed a deficit in the temporal order tasks for remotely acquired information. Neither frontal cognitive deficits nor recognition deficits can account for this patient's poor temporal memory. This retrograde temporal order memory impairment without content memory deficits were not seen in previously reported thalamic amnesic patients. Accordingly, the present patient's poor retrograde temporal memory could hardly be explained by only a thalamic lesion. It is concluded that the patient's impairment of temporal order memory for the retrograde material is probably due to the direct disconnection between the frontal lobe and the hippocampus by disruption of the fornix.

Amnesia↗

PubMed1999

[A case of pure agraphia with a deficit of drawing].

We examined a drawing ability in a case with pure agraphia. The patient, having lesions in the left middle frontal gyrus and inferior parietal lobule, could not write in both dictation and spontaneous writing tasks, with the ability to copy letters being well spared. Correspondingly, he showed a deficit of spontaneous drawing, with the ability to copy complex figures being well spared. These findings suggest that he could have an impairment of retrieving visual image, not restricted to letter image. Although some previous cases with pure agraphia were attributed to an impairment of retrieving visual letter image, drawing ability which seemed to be related to retrieving visual image had not been investigated. In the present case, disability of both writing and drawing could be attributed to a common mechanism, that was an impairment of retrieving visual image. In addition, the patient did not show a significant difference between the performance on Kana writing and on Kanji writing. But it has been said that an impairment of retrieving visual letter image could be related to a deficit of Kanji writing more than of Kana writing. Then, it could be assumed that the mechanism of Kana writing involved not only the pathway depending on graphical motor pattern but one depending on visual image.

Agraphia↗

PubMed1999

Perception and conception: separate memory systems in the medial temporal lobe.

The purpose of the present study was to investigate, by using positron emission tomography, whether the functionally different types of information are subserved by different memory systems in human medial temporal lobe structures. Before explicit retrieval tests during scans, subjects studied words in perceptually and conceptually processed manners separately. It was found that different parts of the medial temporal lobe structures were involved in each of the different conditions. These results indicated that perceptually and conceptually processed types of information were subserved by at least two partially segregated memory systems in human medial temporal lobe structures.

Adult↗

PubMed1998

Age at onset and language disturbances in Alzheimer's disease.

This study examined the effect of age at symptom onset of Alzheimer's disease (AD) on the pattern of language disturbance. We assessed 150 consecutive patients with a clinical diagnosis of mild-to-moderate AD using the Western Aphasia Battery and a 100-item picture-naming test. A multivariate linear regression analysis examined the effect of age at onset after controlling for gender, education, severity of dementia and duration of the disease. Patients with early onset performed significantly worse than did patients with late onset on the word comprehension and sequential commands subtests. On the other hand, late-onset patients performed more poorly than early-onset patients on the picture-naming test in a subgroup with mild language deficits. However, the trend disappeared in other subgroups with more degraded language function. We consider that the concomitant effects of normal aging worsened the picture-naming deficits in the late-onset patients, and the rapid decline of naming ability in the early-onset patients masked the aging effect with the progression of language deficits. The deterioration of word comprehension and the rapid decline of naming ability are the characteristics of early-onset patients. The different patterns of language deficits between early- and late-onset patients may correspond to the genetic heterogeneity of AD.

Age of Onset↗

PubMed1998

Age at onset and visuocognitive disturbances in Alzheimer disease.

We examined the relation of age at onset and visuocognitive disturbances in Alzheimer disease (AD) using a large sample of patients, quantitative neuropsychological measures, and multivariate statistics controlling for gender, education, stage of dementia, and disease duration. Significant positive coefficients were obtained with forward and backward digit and visual spans, visual counting, copying Rey complex figure, and block design task. The results indicated that patients with early-onset AD performed worse than late-onset AD patients on these tasks. There was no significant effect of age at onset on identification of overlapping figures, visual form discrimination, or Raven's colored progressive matrices. These findings confirm the greater attentional and visuospatial impairments in early onset patients when these confounding factors were controlled for, although no significant effect of age at onset in visuoperceptual function was observed.

Age Factors↗

PubMed1998

Lack of association of apolipoprotein E epsilon4 allele dose with cerebral glucose metabolism in Alzheimer disease.

Parietal cerebral glucose metabolism is reduced before substantial impairments appeared in subjects carrying the apolipoprotein E (APOE) epsilon4 allele, but the effect of the APOE epsilon4 allele on cerebral metabolism in Alzheimer disease (AD) is still undetermined. To investigate the effect of the APOE epsilon4 allele on cerebral metabolism in AD, we examined regional cerebral glucose metabolism in 83 patients with AD by using 18F-fluorodeoxyglucose and positron emission tomography. Cerebral glucose metabolism in the fronto-parieto-temporal association and limbic cortices was significantly decreased in the AD patients compared with 26 age- and sex-matched normal controls. Regional cerebral glucose metabolic rate was not correlated significantly with the number of APOE epsilon4 alleles in any region, which was consistent even after controlling the effects of age, sex, and severity of dementia, and in a subgroup analysis of those aged between 60 and 75. These results supported the view that the APOE epsilon4 allele is not associated with specific deficits in brain metabolism in AD despite evidence of preclinical alterations.

Aged↗

PubMed1998

Hypofunction in the posterior cingulate gyrus correlates with disorientation for time and place in Alzheimer's disease.

The relation between orientation for time and place and regional cerebral glucose metabolism was examined in 86 patients with probable Alzheimer's disease of minimal to moderate severity. Regional glucose metabolic rates in the posterior cingulate gyri and in the right middle temporal gyrus were significantly correlated with temporal orientation, and the glucose metabolic rate in the right posterior cingulate gyrus was significantly correlated with locational orientation irrespective of age, sex, education, and memory impairment. The results suggest that dysfunction of these structures plays an important part in producing disorientation in patients with Alzheimer's disease.

Aged↗

PubMed1998

Factors associated with psychotic symptoms in Alzheimer's disease.

OBJECTIVES: Many clinical and biological factors have been reported to be associated with the presence of psychosis in patients with Alzheimer's disease, although the associations were variable. The aim of this study was to clarify factors associated with the presence of psychosis in patients with Alzheimer's disease. METHODS: Psychiatric functioning was studied in 228 patients with Alzheimer's disease based on the results of the behavioural pathology in Alzheimer's disease rating scale or the neuropsychiatric inventory. The effects of sex, education level, age, duration of illness, cognitive function, and apolipoprotein E genotype were investigated for dichotomous psychotic status with a multiple logistic regression analysis. RESULTS: Of the 228 patients with Alzheimer's disease, 118 (51.8%) showed evidence of delusions or hallucinations. Of these, 94 had delusions only, three had hallucinations only, and 21 had both. Older age, female sex, longer duration of illness, and more severe cognitive impairment were the factors independently associated with the presence of psychosis. The presence of psychosis was not significantly related to either educational level or apolipoprotein E genotype. CONCLUSIONS: Age, sex, and severity of illness were independent factors associated with the presence of psychosis in patients with Alzheimer's disease. The reason why some patients with Alzheimer's disease develop psychosis remains unclear. There may be distinctive subtypes of Alzheimer's disease or the presence of individual factors which affect the development of psychosis.

Aged↗

PubMed1998

Alteration of regional cerebral glucose utilization with delusions in Alzheimer's disease.

The authors examined 65 patients with Alzheimer's disease for delusions and explored the relationship of delusions with regional cerebral glucose metabolism determined by [18F]fluorodeoxyglucose PET. In patients with delusions (n = 26), normalized glucose metabolism was significantly increased in the left inferior temporal gyrus and significantly decreased in the left medial occipital region as compared with those without delusions (n = 39). The two groups were similar in age, sex, and dementia severity. These results suggest that delusions in Alzheimer's disease are attributable to a dysfunction in specific brain areas rather than a simple reaction to intellectual deficits.

Aged↗

PubMed1998

Amnestic people with Alzheimer's disease who remembered the Kobe earthquake.

BACKGROUND: Emotional memory is a special category of memory for events arousing strong emotions. To investigate the effects of emotional involvement on memory retention in individuals with Alzheimer's disease we studied peoples' memories of distressing experiences during a devastating earthquake. METHODS: Fifty-one subjects with probable Alzheimer's disease who experienced the Kobe earthquake at home in the greater Kobe area were studied. Memories of the earthquake were assessed 6 and 10 weeks after the disaster in semi-structured interviews, and were compared with memories of a magnetic resonance imaging (MRI) examination given after the earthquake. RESULTS: Forty-four (86.3%) of the subjects remembered the earthquake and 16 (31.4%) of subjects remembered the MRI experience. Factual content of the earthquake was lost in most of the subjects. CONCLUSIONS: Fear reinforces memory retention of an episode in subjects with Alzheimer's disease but does not enhance retention of its context, despite repeated exposure to the information.

Aged↗