|
|
|
Increasing the Temporal Resolution and
Stage Specificity by Visual Adaptive Scoring
(VAS)-A Preliminary Description
Sari-Leena Himanen, Ph.D., Antti Saastamoinen, Ph.D.,
and Joel Hasan, Ph.D.
The scoring system of Rechtschaffen and Kales (1968)is practically the only method of
visual sleep analysis in spite of its serious drawbacks.The most important ones are the
fixed,long epochs,the insufficient number of sleep stages and the ignorance of EEG
topography.In this preliminary work a method to overcome these limitations in visual
scoring is presented.Segments of variable length and more stage categories than in the
standard system were used.The method was preliminarily applied to the analyses of
multiple sleep latency tests (MSLT)from three subjects.All recordings were classified
both by the standard method of Rechtschaffen and Kales (RKS,1968)and by visual
adaptive scoring (VAS).VAS was more sensitive to short sleep spells than RKS and gave
a shorter and according to our opinion a more accurate sleep onset latency.The rating of
two subjects changed from borderline to pathological.One became more normal because
of different scoring of one segment.The percentages of stages obtained by VAS were only
slightly different from those obtained by RKS and did not reach statistical significance.Yet,
the infrastructure,short lapses of alertness,short sleep episodes and arousals,were more
precisely revealed.Although VAS is sometimes more time consuming than traditional
scoring it is a model that fits the sleep/wake process more closely than RKS and can
therefore be regarded as a better model.The improved temporal resolution gives
electrophysiologically more stationary epochs.This will be especially important with
computer analysis.When used for scientific work VAS helps to provide more profound
understanding of underlying mechanisms of sleep and arousal as well as their correlates.
Sometimes VAS is also easier to apply because many of the problems with RKS are due
to the epoch boundaries and landmarks not fitting the stage categories.(Sleep and
Hypnosis 1999;1:22-28)
| Keywords: visual scoring, sleep stages, adaptive segmentation, sleep analysis. |
|
|
| To download full text of articles please |
|
|
| |
|
Publisher:
|
