Search PubMed⌕ Search

Biomedical subjects

P Ktonas

Publications and source records attributed to P Ktonas.

6 recordsLinked to original sources
PubMed2003

Two-minute rapid eye movement (REM) density fluctuations in human REM sleep.

Rapid eye movement (REM) density fluctuations during REM sleep were studied in five healthy young adults (23-26 years of age). Appropriate electro-oculographic (EOG) montage and automated EOG analysis enabled the detection of horizontal, vertical, and oblique REMs. REM density time series based on these REMs were formed for all the REM periods of the subjects. Autoregressive (AR) spectral analysis of the REM density time series estimated periodicities in the range of 1.7-2.4 min for 14 of the 16 REM periods analyzed, regardless of duration or number of REMs. Four subjects had such periodicities in each of their REM periods and the fifth subject had such periodicities in half the REM periods. This REM density fluctuation at a periodicity of about 2 min may relate to an important 'rhythmic' component of the REM generating mechanism(s).

Adult↗
PubMed2001

The organization of rapid eye movement activity during rapid eye movement sleep is further impaired in very old human subjects.

Rapid eye movement activity (REMA) during rapid eye movement (REM) sleep was studied in seven very old ('old-old') subjects. Beyond global quantitative features (REMA density), we evaluated the organizational aspects of REMA, that is its occurrence in burst mode, which were compared to a group of younger elderly subjects ('young-old'). REMA density in 'old-old' subjects is not significantly different from that of 'young-old' subjects. The same lack of difference in the two groups is found for the number of REMA bursts. By contrast, the duration of REMA bursts is reduced in the 'old-old' subjects, as well as the 'burst state-to-burst-state' probability, i.e. the probability for successive inter-REMA time intervals to be part of the same REMA burst. Our results clearly show that the trend towards an impairment of REMA organizational aspects continues with aging. This is consistent with the hypothesis that sleep disorganization keeps worsening with age. However, it is of interest to observe that the capability of producing REMA bursts is preserved despite aging.

Age Factors↗
PubMed1999

The organization of rapid eye movement activity during rapid eye movement sleep is impaired in the elderly.

Rapid eye movement activity (REMA) during rapid eye movement activity (REM) sleep was studied in eight elderly subjects and six young adults as a control group. Beyond global quantitative features (REMA density), we evaluated the organizational aspects of REMA, that is its occurrence in burst mode, still largely unknown in the aged. REMA density in the elderly is not significantly different than that of young adults. By contrast, the duration of REMA bursts is reduced in the elderly, as well as the 'burst state-to-burst-state' probability, i.e. the probability for successive inter-REMA time intervals to be part of the same REMA burst. These results show that global aspects of the quantitative features of REMA are preserved in the elderly, whereas their organizational aspects are impaired. These data are consistent with the hypothesis that aging is associated with a difficulty in maintaining physiological processes over time.

Adult↗
PubMed1999

Delta (0.5-1.5 Hz) and sigma (11.5-15.5 Hz) EEG power dynamics throughout quiet sleep in malnourished infants.

The present study aimed to quantify, through power spectral analysis, the dynamics (temporal pattern and temporal interrelationship) of the EEG power in the low-delta (delta) and in the sigma-spindle (sigma) frequency band during quiet sleep (QS) in 5 malnourished infants (MI), 5.5 to 13.5 months old, and in 5 age-matched, healthy control infants (CI). Malnutrition results in modification of the temporal pattern of delta and sigma band power during QS. The delta band power increases faster in MI than in CI, leading to higher power levels in MI at the same time segment. However, the overall trend of the delta band power throughout QS is similar in MI and CI. The premature ending of QS phases (uninterrupted QS periods), and the reduced total amount of QS which have been reported in MI could result in an increased slow wave sleep (SWS) "pressure". This SWS pressure could account for both the higher level and the faster increase of the delta band power during the QS phase which are found in MI when compared to CI.

Electroencephalography↗
PubMed1975

Computer aided nystagmus analysis.

The electronystagmogram (ENG) is analyzed with the assistance of a PDP-8 minicomputer for calculating the instantaneous slope, average slope, lead frequency, lag frequency and cycle frequency of both the fast and slow wave components of the ENG. The ENG data is first digitized and displayed on a storage scope in order to permit the operator to select an epoch of data. The results are then displayed on the scope, and the mean and variance of the important parameters are outputted on the teletype. The programs include a system for storing a large library of records.

Computers↗