Biomedical subjects

Koichi Sameshima

Publications and source records attributed to Koichi Sameshima.

5 recordsLinked to original sources

PubMed2006

[Biologic artifacts in quantitative EEG].

We studied the influence of five biologic artifacts sources on quantitative EEG (blinking, forced eyes closure, forced jaw closure, tongue movements and pursuit eyes movements) through both visual and spectral analysis, with the purpose of verifying how do these artifacts can be seen in a cartographic way. We found that the spectrums potentials showed the same topographic display that was found through visual analysis. Visual analysis was superior than the quantitative evaluation to recognise the artifacts, as the former preserved the morphological display of the paroxysms. However it is important know how do the potentials are represented in quantitative maps, so that they can be identified as artifacts and not as pathologic EEG activity.

Adult↗

PubMed2006

Comments on 'Is partial coherence a viable technique for identifying generators of neural oscillations?': Why the term 'Gersch Causality' is inappropriate: common neural structure inference pitfalls.

To aid prospective neural connectivity inference analysts and hoping to preclude misconception spread, we exploit the didatic value of some of the issues raised by Albo et al. (Biol Cybern 90: 318-326, 2004) who claim that signal-to-noise ratio (SNR) values can lead to mistakes in structural inference when using partial coherence in connection to Gersch's 1970 method for spotting signal sources (Gersch in Math Biosci 14: 177- 196, 1972). We show theoretically that Gersch's method is able only to spot which measurement of some common underlying factor has the least amount of additive noise and that this has nothing to do with any reasonable notion of 'causality' as suggested by Albo et al. (Biol Cybern 90: 318-326, 2004). We also show that despite the inherent structural ambiguity of the model used by Albo et al. (Biol Cybern 90: 318-326, 2004) to back their claim, its data can nonetheless furnish the correct time precedence hierarchy between the activities in its measured structures, both when simple (correlation) and more sophisticated methods are used (partial directed coherence) (Baccala and Sameshima in Biol Cybern 84:463-474, 2001a) in a true depiction of time series causality.

Animals↗

PubMed2005

[Decline of cognitive capacity during aging].

Decline of cognitive capacity (DCC) is due to normal physiological aging processes or to pre-dementia stage. Epidemiological studies show that elderly with decline of cognitive capacity have higher risk to develop Alzheimer's disease (AD), especially those with episodic memory deficits. This review presents the most important diagnosis criteria, neuropathological and neuropsychological findings of decline of cognitive capacity during aging.

Aged↗

PubMed2005

[EEG alpha band coherence analysis in healthy adults: preliminary results].

We studied the occipital inter-hemispheric coherence of Electroencephalogram (electrodes O1-O2) for alpha band (alpha1--8.0 to 10.0 Hz and alpha2--10.1 to 12.5 Hz) in two groups of healthy individuals (young adults and subjects older than 50 years-old), to assess if there is significant difference between this two age groups. No significant difference in alpha band coherences was found between these two age groups.

Adult↗

PubMed2004

Graph theoretical characterization and tracking of the effective neural connectivity during episodes of mesial temporal epileptic seizure.

Via a detailed case study of mesial temporal lobe epilepsy, we show that a method of determining the direction of information flow among signals is able to provide focal localization via the simultaneous analysis of multiple EEG channels. This determination is accomplished by representing information flow direction via directed graphs, where focal electrodes are associated with high observed rates of pertinence to strongly connected subgraphs. Further clinical support to this finding is provided by results for an additional 9 cases of focal epilepsy cases. The graph theoretical approach is a tool for describing and analyzing the effective connectivity dynamics behind epileptic seizures and may provide a common language for studying other complex dynamic relationships between neural structures.

Electroencephalography↗