Biomedical subjects

Joel Hasan

Publications and source records attributed to Joel Hasan.

21 records · Page 2Linked to original sources

PubMed2002

Spindle frequencies in sleep EEG show U-shape within first four NREM sleep episodes.

It has been shown in previous studies on sleep electroencephalogram (EEG) that spindles are slower in the beginning of the night fastening towards the end of the night. Corresponding findings have been obtained by spectral analysis. The present study was based on our preliminary observation that slower spindles are found in the middle of the non-rapid eye movement (NREM) sleep episodes as compared with the beginning or the end of the episodes. Eight healthy female and six male subjects were studied. Sleep spindles were visually selected and spindle frequencies calculated for 11 analysis points in each NREM sleep episode. The median spindle frequencies formed a clear U-shape within NREM sleep episodes with an initial decrease and final increase. The decrease was statistically significant within the first four NREM sleep episodes. It is possible that the spindle frequency pattern could be used to reveal variations in sleep depth within sleep stage 2. In animal studies the spindle frequency has been found to be associated to the duration of the hyperpolarization-rebound sequences of the thalamocortical cells. If it is assumed that the same cellular mechanisms are responsible for spindle frequencies in humans then the study of variations in spindle frequency could be used to examine the NREM sleep process in humans.

Adult↗

PubMed2002

A study on gender and age differences in sleep spindles.

In the present work, gender differences in sleep spindle topography were examined in 40 subjects. Their median age was 32 years (range 22-49 years). Spindles were detected from 3,306,060 s of visually scored stage 2 sleep EEG by a previously validated automatic fuzzy detector at 1-second intervals. A total of 271,168 spindles were found from the six EEG channels analyzed. Females showed a significantly higher percentage of spindles in the left frontal channel than males (Fp1-A2; p = 0.026). To confirm that this difference was gender and not age related, the subjects were divided into two age groups. No significant differences in spindle activity of the frontal channels were found between the groups. However, the interindividual spindle variability seemed to be at least as large as that stemming from gender.

Adult↗

PubMed2000

Limitations of Rechtschaffen and Kales.

The guidelines of Rechtschaffen and Kales (R&K) were meant as a reference method. However, it became, unintentionally, a gold standard. The rules have never been appropriately validated. It is used for the scoring of recordings of, for instance, pathological sleep, for which it was not designed. Today R&K is an insufficient description of sleep processes. In practice, the rules are often difficult or impossible to follow and deviations are common, although not reported. The major drawbacks are: low temporal resolution, ignorance of spatial information, insufficient number of stages, low correspondence between electrophysiological activity and stages, and ignorance of other physiological parameters such as autonomous nervous system activity and body motility. The original idea of the committee should be followed; the guidelines should be revised with the accumulation of new knowledge and development of technology. This is especially true for the analysis of delta waves, which should replace visual scoring of the NREM sleep stages. Many of the problems related to the use of the manual are not due to the system itself but the way it has been applied. This has evidently had a serious impact on the way of thinking and the development of the field in general.

Journal Article↗