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Biomedical subjects

Toshiaki Kamitani

Publications and source records attributed to Toshiaki Kamitani.

9 recordsLinked to original sources
PubMed2006

Autopsy case of Creutzfeldt-Jakob disease with Met/Val heterozygosity at codon 129 and type 1 protease-resistant prion protein presenting some florid-type plaques and many Kuru plaques in the cerebellum.

We report an atypical case of CJD. The clinical course was similar to a classic CJD phenotype, but histopathological study revealed several florid-type plaques in the amygdale and abundant Kuru plaques in the cerebellum that are atypical of classic CJD. Molecular analysis showed methionine/valine heterozygosity at codon 129 and no pathogenic mutation in the coding region of the prion protein gene. Western immunoblots revealed type 1 protease-resistant prion protein (PrPres), and a ration analysis of PrPres showed a high ratio of the diglycosylated form and a low ratio of the non-glycosylated form. Our case could not be precisely classified in any of Parchi's six variants. It suggests the existence of some factors that determine the phenotypic variability other than the codon 129 genotypes in the PrP gene or the physicochemical properties of PrPres.

Autopsy↗
PubMed2005

Visual event-related potentials under different interstimulus intervals in Parkinson's disease: relation to motor disability, WAIS-R, and regional cerebral blood flow.

We have introduced S1-S2 paradigm (task S) as well as oddball paradigm (task O) visual event-related potentials (ERPs) under different interstimulus intervals (ISIs) in Parkinson's disease (PD). ERP measurements were correlated with motor disability, WAIS-R, and regional cerebral blood flow (rCBF). The 'group' influence was characterized by longer latency for P300, N200, and reaction time and decreased P300 amplitude in PD. Both P300 latency and reaction time during task O showed significantly longer latency in longer ISI condition. Our results revealed 'ISI' influence on ERPs during task S and significant correlation between ERPs and rCBF in task S.

Aged↗
PubMed2004

Visual evoked potential changes related to illusory perception in normal human subjects.

To study the human brain activity correlated with illusory perception, we chose a physically flat plane figure which looks like a convex figure. We studied visual evoked potential (VEP) changes, which reflect perceptual properties of illusory perception. We defined two paradigms, an illusory paradigm (IP) and a control paradigm (CP). Two stimuli, A and B, were randomly presented in the IP, while stimuli C and D were randomly presented in the CP. Stimulus A was the only figure which looked like a convex figure. A three-way analysis of variance was applied to the VEP components in each paradigm, with three factors: figures, electrodes, and sessions. Different configuration patterns between the two paradigms explained different grand mean VEP waveforms between the two paradigms; a greater N1 for the CP, a greater P1 for the IP, and marked attenuation of the N3 and P3 components for the IP. Significant main effects of figures only for the IP were found on P1 and P1N2 amplitude and P2 latency, which are assumed to reflect perceptual properties of stereoscopical illusory perception.

Adult↗
PubMed2003

The effect of stimulus-onset asynchrony on human visual event-related potentials during simple and choice reaction paradigms under constant or random conditions.

Visual event-related potentials (ERPs) were recorded during an oddball paradigm (OBP) and a simple reaction paradigm (SRP) to investigate the effect of stimulus-onset asynchrony (SOA) on ERPs under constant and random conditions in nine healthy individuals. NA was obtained by subtracting ERPs for SRP from those to the frequent nontarget of OBP. N2 was obtained by subtracting ERPs to the frequent nontarget from those to the rare target of OBP. N1, P2, and P3 latencies during OBP were shorter, and N1 amplitude of OBP, P1, and P2 amplitude of SRP, and NA amplitude were larger under constant conditions than under random conditions. We suggest that visual information processing is faster and more effective under constant conditions than under random conditions. NA potential related to the pattern recognition processing was significantly interfered with under random conditions, whereas N2 potential related to the stimulus classification was less influenced by the rhythm. The visual selective processing activity was influenced by the SOA with the positive shift of the waveform "20% rare target of OBP-100% target of SRP" under random conditions.

Adult↗
PubMed2003

Early sensory information processes are enhanced on visual oddball and S1-S2 tasks in Parkinson's disease: a visual event-related potentials study.

To observe sensory and cognitive information processing in Parkinson's disease (PD), 34 PD patients and 26 controls were investigated. A visual oddball paradigm and an S1-S2 paradigm were employed to record the early (P1, N1, P2) and late (N2, P3) event-related potentials (ERPs) at Cz, Pz and Oz. Results showed: (1) enlarged P1 amplitude at all electrode locations on both tasks, (2) shortened N1 latency and enlarged P2 amplitude at Oz on both tasks, (3) enlarged N1 amplitude at Cz during an oddball paradigm, (4) delayed N2 latency and decreased N2, P3 amplitude on both tasks, and (5) delayed P3 latency and reaction time during the S1-S2 paradigm. Abnormal ERP changes were correlated with worsened scores on Wechsler Adult Intelligence Scale-Revised and motor dysfunction scales in PD. We surmise overactive aspects or failed inhibitory modulation of sensory information processing in the early ERP stage and deficient cognitive information processing during the late ERP stage in PD.

Adult↗
PubMed2003

Event-related potentials during visual S1-S2 paradigm in multiple system atrophy: relation to morphologic changes on brain MRI measurement.

Although mild cognitive deficits in multiple system atrophy (MSA) have been proved on neuropsychological testing, the cognitive function in MSA has not been investigated sufficiently from an electrophysiological view point. We performed a visual Event-related potential (ERP) examination and quantitative magnetic resonance imaging (MRI) measurements on 24 MSA patients and 18 normal subjects, and investigated the relationship between the ERP abnormalities and the morphological changes of the brain in MSA patients. To elicit ERPs, we used S1-S2 task which needs frontal lobe function for execution. We found significant prolongation of P3 latency and reaction time and significant attenuation of P3 amplitude in MSA, compared with normal control values. We performed the square and linear MRI measurements on MSA and normal subjects. The cerebellum, the pons, the perisylvian cerebral area and the deep cerebral gray matter in MSA were significantly smaller than those in normal subjects. The mean value in MSA was significantly increased for the bicaudate index and Huckman number compared with those in normal subjects. In MSA, we found significant correlation between P3 latency and atrophy of the cerebellum and the pons, while we found no correlation between ERP abnormalities and quantitative MRI measurements of any other regions. Our results showed that the prolongation of visual P3 latency during S1-S2 task was significantly associated with atrophy of the cerebellum and the pons.

Aged↗
PubMed2002

Visual event-related potential changes in two subtypes of multiple system atrophy, MSA-C and MSA-P.

We investigated the visual event-related potentials (ERPs) in two subtypes of multisystem atrophy (MSA) in 15 MSA-C patients, 12 MSA-P patients, and 21 normal control (NC) subjects. We used a visual oddball task to elicit ERPs. No significant changes were seen in N1 or N2 latency, in either MSA-C or MSA-P, compared with the NC group. An early stage of visual information process related to N1 and a visual discrimination process related to N2 might be preserved in both MSA-C and MSA-P. The P3a peak was more frequently undetectable in MSA than in the NC group. Significant P3a amplitude reduction in both MSA-C and MSA-P suggests impairment of the automatic cognitive processing in both MSA-C and MSA-P. Significant difference was found in P3b latency and P3b amplitude only in MSA-C, compared with the NC group. The result suggests the impairment of the controlled cognitive processing after the visual discrimination process in the MSA-C group. We further investigated the correlation between visual ERP changes and magnetic resonance imaging (MRI) data. Quantitative MRI measurements showed reduced size of the pons, cerebellum, perisylvian cerebral area, and deep cerebral gray matter in both MSA-C and MSA-P, and of the corpus callosum only in MSA-P, as compared to NC group. In both MSA-C and MSA-P, P3b latency was significantly correlated with the size on MRI of the pons and the cerebellum. P3b latency in the whole MSA group was also significantly correlated with the size of the pons and the cerebellum. These results indicate that P3b latency changes in parallel with the volume of the pons and the cerebellum in both MSA-C and MSA-P.

Adult↗