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A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects
644
BOOK REVIEWS
A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. - - A. Reehtschaffen and A. Kales (Editors). (Public Health Service, U.S. Government Printing Office, Washington, D.C., 1968, 58 p., $4,00). Tonic variability of EEG amplitude and frequency has become a measure of clinical and experimental interest since the description of a 90 rain cycle within human sleep fifteen years ago. The division of this cycle into discrete phases or stages is important as understanding of its norreal regulation, functional significance, and pathological disorder are sought. Thus the sequence, duration, and periodicity of sleep stages have been considered as dependent variables in psychophysiological experiments and in relation to structural and functional diseases of the nervous system and as independent variables in deprivation experiments. As such, their precise quantification is desirable and it is to this end that the Manualis directed. As the authors point out, it is to the credit of the Chicago group, and principally to Dement, that this need was early recognized and squarely met --- through the informal distribution of staging criteria within the circle of investigators that has since spread the news. This publication now more formally presents the Dement criteria. The text argues well for the terminology and definitions used in the staging of sleep polygraphic records. The importance of combining EEG and EMG data is stressed in differentiating Stage W from Stage REM. This differentiation, on EEG criteria alone, is even more difficult than indicated here since some subjects show quite wellorganized runs of alpha activity with eye movement when behaviorally asleep. These and related arguments would have been even more cogent had the authors provided some data as to the reliability of using their scoring method. A more extensive bibliography featuring a comprehensive survey of normative data on human sleep stage parameters would also have strengthened the text: The reader is warned that the criteria apply only to adult human subiects but "'adult" is not defined and no direction to the appropriate literature on the ontogeny of human sleep is offered. The introductory figures (1-9) illustrate electrode placement, show typical records of the several stages, and resolve ambiguous situations through schematic drawings. In these, as in the later tracings, the apparent technical superiority of records taken with the Offner machine (Fig. 2, 3, 9-32) would have been greatly reduced by providing the Grass instrument used (Fig. 4, 5, 33-40) with a new set of pens. The balance of the tracings (Fig. 9-40) repeats the sequence of stages for each of three subjects, all male students, ages 19, 21 and 25. The redundancy in choice of subjects is unfortunately repeated in many of their records. According to my analysis, only 13 of the 32 figures are needed to convey the desired information and, at that, 4 of the introductory figures are essentially duplicated, tn presenting a series of subjects, the authors might have selected them for important differences such as age, sex, or prominence of alpha in waking, etc. The authors imply that the scoring system represents
the consensus of many investigators including some who have worked independently of the Chicago group. Actually four of the twelve authors are trainees of the Chicago school (Dement, Monroe, Rechtschaffen and Roffwarg), two pairs are independent co!laborators (Berger and Oswald from Edinburgh, and Jacobson and Kales from UCLA), and the four others are not known to me as authors of extensive parametric work on human sleep stages. One might, therefore, more conservatively state that the work represents the consensus of workers from three human sleep laboratories. The absence of representation from other labs, especially Webb's Florida group, which is second only to the Chicago group in experience but quite complementary because of its interest in Stage 4, is therefore puzzling. An important assumption of the work is that the variables to be measured by the method described are sensitive indices of biological events. It seems intuitively likely to me that the duration of a state may be a relatively insensitive index insofar as it ignores the intensity of phenomena within an epoch of time. In distinguishing stages IV from III, for example, the degree to which the tracing exceeds 50 ~ delta is ignored. Experiments in animals have shown that the intensity of synchronization may be more sensitive to experimental manipulation than its duration. And it is now apparent that REM intensity, in man, is more variable than REM duration. A more serious problem is that the work may become obsolete before it is useful to the end that it is dedicated, namely the quantification of sleep stages. This is true for several reasons: (I) the human sleep cycle is more rigid than variable, hence the use of temporal parameters of sleep as dependent variables is extremely frustrating as a strategy, (2) achieving significance in small differences requires large numbers and a single experiment requires 8 subject hours and 8 technici~an hours (usually at night) simply to perform and at least 2 more technician hours to score following the Manual. It would seem that if such work is to be done, the Manual would be most useful as a first step toward the design of computer programs for automatic analysis of tape recorded data. It is perhaps too much to expect of this book at this timei but the desirability of totally objective and automatic data analysis in this field should certainly be considered as the criteria are further applied and modified. I wonder if the method of sleep staging measures the right thing in the right way and if so, I can only hope that strategic and technical innovations will soon obviate these crude and tedious scoring techniques. In summary, I would commend the work for its descriptive, illustrative, and quantitative approach to sleep staging in the young adult, but regret its lack of comprehensiveness, its redundancy, and failure to establish its reliability. It belongs in the library of every sleep and EEG laboratory, but is still far from a standard work. J. ALLAN HOBSON, M.D.
Department of Psychiatry, HarL,ard Medical School, Boston, Mass. 02115 (U.S.A.)
Electroenceph. c/in. Neurophysiol., 1969, 20:644
BOOK REVIEWS
A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. - - A. Reehtschaffen and A. Kales (Editors). (Public Health Service, U.S. Government Printing Office, Washington, D.C., 1968, 58 p., $4,00). Tonic variability of EEG amplitude and frequency has become a measure of clinical and experimental interest since the description of a 90 rain cycle within human sleep fifteen years ago. The division of this cycle into discrete phases or stages is important as understanding of its norreal regulation, functional significance, and pathological disorder are sought. Thus the sequence, duration, and periodicity of sleep stages have been considered as dependent variables in psychophysiological experiments and in relation to structural and functional diseases of the nervous system and as independent variables in deprivation experiments. As such, their precise quantification is desirable and it is to this end that the Manualis directed. As the authors point out, it is to the credit of the Chicago group, and principally to Dement, that this need was early recognized and squarely met --- through the informal distribution of staging criteria within the circle of investigators that has since spread the news. This publication now more formally presents the Dement criteria. The text argues well for the terminology and definitions used in the staging of sleep polygraphic records. The importance of combining EEG and EMG data is stressed in differentiating Stage W from Stage REM. This differentiation, on EEG criteria alone, is even more difficult than indicated here since some subjects show quite wellorganized runs of alpha activity with eye movement when behaviorally asleep. These and related arguments would have been even more cogent had the authors provided some data as to the reliability of using their scoring method. A more extensive bibliography featuring a comprehensive survey of normative data on human sleep stage parameters would also have strengthened the text: The reader is warned that the criteria apply only to adult human subiects but "'adult" is not defined and no direction to the appropriate literature on the ontogeny of human sleep is offered. The introductory figures (1-9) illustrate electrode placement, show typical records of the several stages, and resolve ambiguous situations through schematic drawings. In these, as in the later tracings, the apparent technical superiority of records taken with the Offner machine (Fig. 2, 3, 9-32) would have been greatly reduced by providing the Grass instrument used (Fig. 4, 5, 33-40) with a new set of pens. The balance of the tracings (Fig. 9-40) repeats the sequence of stages for each of three subjects, all male students, ages 19, 21 and 25. The redundancy in choice of subjects is unfortunately repeated in many of their records. According to my analysis, only 13 of the 32 figures are needed to convey the desired information and, at that, 4 of the introductory figures are essentially duplicated, tn presenting a series of subjects, the authors might have selected them for important differences such as age, sex, or prominence of alpha in waking, etc. The authors imply that the scoring system represents
the consensus of many investigators including some who have worked independently of the Chicago group. Actually four of the twelve authors are trainees of the Chicago school (Dement, Monroe, Rechtschaffen and Roffwarg), two pairs are independent co!laborators (Berger and Oswald from Edinburgh, and Jacobson and Kales from UCLA), and the four others are not known to me as authors of extensive parametric work on human sleep stages. One might, therefore, more conservatively state that the work represents the consensus of workers from three human sleep laboratories. The absence of representation from other labs, especially Webb's Florida group, which is second only to the Chicago group in experience but quite complementary because of its interest in Stage 4, is therefore puzzling. An important assumption of the work is that the variables to be measured by the method described are sensitive indices of biological events. It seems intuitively likely to me that the duration of a state may be a relatively insensitive index insofar as it ignores the intensity of phenomena within an epoch of time. In distinguishing stages IV from III, for example, the degree to which the tracing exceeds 50 ~ delta is ignored. Experiments in animals have shown that the intensity of synchronization may be more sensitive to experimental manipulation than its duration. And it is now apparent that REM intensity, in man, is more variable than REM duration. A more serious problem is that the work may become obsolete before it is useful to the end that it is dedicated, namely the quantification of sleep stages. This is true for several reasons: (I) the human sleep cycle is more rigid than variable, hence the use of temporal parameters of sleep as dependent variables is extremely frustrating as a strategy, (2) achieving significance in small differences requires large numbers and a single experiment requires 8 subject hours and 8 technici~an hours (usually at night) simply to perform and at least 2 more technician hours to score following the Manual. It would seem that if such work is to be done, the Manual would be most useful as a first step toward the design of computer programs for automatic analysis of tape recorded data. It is perhaps too much to expect of this book at this timei but the desirability of totally objective and automatic data analysis in this field should certainly be considered as the criteria are further applied and modified. I wonder if the method of sleep staging measures the right thing in the right way and if so, I can only hope that strategic and technical innovations will soon obviate these crude and tedious scoring techniques. In summary, I would commend the work for its descriptive, illustrative, and quantitative approach to sleep staging in the young adult, but regret its lack of comprehensiveness, its redundancy, and failure to establish its reliability. It belongs in the library of every sleep and EEG laboratory, but is still far from a standard work. J. ALLAN HOBSON, M.D.
Department of Psychiatry, HarL,ard Medical School, Boston, Mass. 02115 (U.S.A.)
Electroenceph. c/in. Neurophysiol., 1969, 20:644