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biofeedback offers a behavioral approach to the maintenance of optimal physiological functioning in the aged.
In addition to the implications of biofeedback as a therapeutic technique are the implications for feedback as an experimental technique. Increasing emphasis has been placed on the need for experimental as well as descriptive research in the psychology of aging (Baltes & Goulet, 1971; Birren, 1971), and biofeedback is a tool which can be used for experimental manipulation. It is possible to train subjects with biofeedback to maintain physiological rates of young and old individuals. In this manner simulation of the observed physiological age functions can be achieved. Using behavioral mensures as the dependent variable in such age simulation studies might clarify the nature of the relationship between aging, physiology and behavior.
An age simulation study using the biofeedback technique to train subjects to control the frequency of their alpha rhythm is currently underway in our labora. tory at the University of Southern California. A group of young and a group of old subjects is learning to increase the time they spend in three different frequencies in the alpha range (fast, mean, slow). After a baseline session in which EEG and reaction time are measured the biofeedback technique is used to train subjects to increase the time spent in their mean brain wave frequency (normally 10-11 cps for young and 8-9 cps for old subjects). Subjects' brain waves are moni. tored with an EEG amplifying system, the EEG output is filtered, and when the filtered EEG signal reaches a selected amplitude it triggers a feedback tone heard by the subject. Subjects are told that their brain waves control the tone and that they are to keep the tone on as long as possible. When subjects meet a set cri. terion of time spent in the alpha state, reaction time is measured. Next subjects learn to increase the time spent in brain wave frequencies two cps faster and two cps slower than their mean frequency, and reaction time is measured after subjects accomplish each task. The conditions are counterbalanced so that half of the subjects receive the speed condition first and the slow condition second while half receive the conditions in the reverse order.
Surwillo (1963) demonstrated in a descriptive study that brain wave duration (inverse of frequency) correlated highly (r=.72) with simple reaction time, and he hypothesized that the slowing of brain wave frequency with age could account for the age related slowing in reaction time. The present study is an experimental test of Surwillo's hypothesis. Half of the subjects have completed the experiment, and preliminary results indicated that three-fourths of the old and half of the young subjects shifted their reaction time by at least 20 msec, in the direction predicted by Surwillo's hypothesis. Hence, preliminary results suggest that there is a relationship between simple reaction time and brain wave frequency. At least some of the observed slowing of reaction time in the aged may be related to slowing of the dominant brain wave frequency.
The slowing of reaction time is not the only behavior which has been linked to the slowing of the dominant brain wave rhythm. Nowlis (1970) suggested that biofeedback training of the EEG alpha rhythm might help geriatric patients to maintain alertness over longer periods of time thereby recovering deficits in cognitive functioning. Mood changes have also been related to changes in alpha frequency (Davis, 1942; Hurst, Mundy-Castle, & Beerstecher, 1954). The design strategy of training subjects through biofeedback to increase the time spent in fast, mean and slow brain wave frequencies presents a means of testing the behavioral significance of the slowing of the alpha rhythm with age. A comparable strategy could be adopted to test the behavioral significance of age changes in blood pressure and any number of other physiological rates which are known to change with age. If deleterious behavioral changes are found to relate to the physiological changes, biofeedback might be used to train subjects to maintain an optimal physiological rate hence reversing the change in behavior. In this manner the biofeedback technique is potentially useful as a therapy and as a technique for the scientific study of aging.
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THE USEFULNESS OF THE LIFE-SPAN APPROACH FOR THE PSYCHOPHYSIOLOGY OF
(Diana S. Woodruff, PhD')
The life-span perspective has been both useful and misleading in psycho physiological approaches to aging, and it is the aim of this paper to delineate the strengths and weaknesses of the life-span model in psychophysiological research. Psychophysiology involves the attempt to determine relationships between psychological and physiological variables. Psychophysiological research on aging has typically consisted of the description and explanation of age changes in behavior over the life-span in terins of age changes in physiology. Indeed, the biological decremental model of aging has pervaded geropsychological research, and consequently the psychophysiological approach has received considerable emphasis in the psychology of aging.
On the one hand, the life-span approach in psychophysiology has been useful inasmuch as a large body of evidence has accumulated indicating that physiological decline is related to age changes in behavior (e.g., Birren, Butler, Greenhouse, Sokoloff, & Yarrow, 1963; Gaitz, 1972; Jarvik, Eisdorfer, & Blum, 1972; Thompson, 1973; Welford & Birren, 1965). On the other hand, the approach has perhaps misdirected psychologists to accept irreversible physiological and behavioral decline as characteristic of aging thus precluding exploration of means to decelerate or reverse behavioral aging as well as precluding exploration of non-physiological and concurrent environmental determinants. The pervasiveness of the life-span psychophysiological approach in aging research attests to the usefulness of this approach, but the very pervasiveness of the biological decremental model represents a weakness in terms of a narrowness of perspective in contemporary geropsychological research.
1 Assistant Research Psychologist, Dept. of Psychology, Univ. of California, Los Angeles PSYCHOPHYSIOLOGY OF THE AGED: PAST A PROLOGUE FOR THE FUTURE?
In evaluating the usefulness of the life-span perspective for understanding behavior in the aged, one is essentially evaluating the usefulness of information about the early and middle years of life in understanding and predicting be havior in later years. In this regard the question, “Past a prologue for the future?” involves the degree to which historical events in the life-span are antecedents for behavior in the future (see Baltes, this symposium). Another sense of this question can also be discerned : Are the past means of studying the psycho;>!ysiology of aging necessarily the most useful prologue for future approaches in this area? Perceived at this level, the question involves methodology. The rescluiion of the second issue in part rests on the resolution of the firstthe extent to which past history is useful in understanding behavior in the aged.
Historical vs. concurrent predictors.-Psychophysiologists have found descriptive life-span data useful in the identification of potential antecedents for behavioral changes in the aged. Biologists have clearly documented a continuous gradual decline in physiological efficiency of about 1% per year in the decades between the ages of 30 and 80 (e.g., Chinn, 1969; deVries, 1969; Shock, 1962; Timiras, 1972). Since one approach of psychophysiologists is to explain behavior in terms of physiology, it is essential for psychophysiologists to be able to account for behavior-physiology relationships over this period when physiological function is known to change. While current retirement practices arbitrarily set the onset of old age at the 65th birthday, physiological aging has no such sudden onset. For this reason psychophysiologists must be aware of historical as well as concurrent physiology-behavior relationships to accurately explain behavior in the aged.
In observing an old organism without knowledge of the gradual change in physiological capacity, psychophysiologists might predict dramatically different behavioral effects. Gradual versus sudden onset of a physiological deficit have different behavioral consequences. For example, in animal lesion studies, the behavioral consequences of a large lesion made in a single operation are much more dramatic than the behavioral consequences of several smaller lesions in which over a period of time an amount of tissue is removed equal to that removed in a single large lesion. In the same manner, the EEG record of an individual displaying a slowed dominant frequency and an increase in diffuse slow activity would probably be accompanied by severe behavioral deficiencies if the onset of such changes was recent or the result of a concurrent change in the environment (e.g., as in sensory deprivation or oxygen insufficiency to the brain), whereas the gradual onset of such EEG changes which occur to some degree in all aging individuals appear to be accompanied only with subtle behavioral changes (Obrist, 1965; Surwillo, 1968 ; Thompson, 1973). Hence, to the develop mental psychophysiologist it is essential to be aware of rates of change in physiological and behavioral variables, and in this sense historical or life-span data as well as concurrent information are required.
Other instances when historical psychophysiological information is essential occur when there are late-life consequences of early events. To predict and ex plain why the aged cohort in the year 2020 will have selectively greater hearing loss than preceeding cohorts, gerontologists will find it useful to know that this cohort experienced extensive exposure to highly amplified rock music early in their life-span. To predict the occurrence of cardiovascular disease in middleaged men, historical information on psychosocial and behavioral factors has proved useful (Friedman, 1969; Hinkle, Whitney, Lehman, Dunn, Benjamin, King, Plakun, & Fleninger, 1968; Shekelle, Ostfeld, & Paul, 1959). In instances such as these, concurrent information gives only partial clues to the causes of behavioral and physiological changes, and the life-span perspective proves es. sential to understanding physiology and behavior in late life.
Continuity vs. discontinuity models.-While historical psychophysiological information can be useful in understanding behavior in the aged, there are instances when historical psychological-behavior relationships are irrelevant for such an understanding. Physiological variables which have no effect on behavior when they are within a normal range in young individuals may dramatically affect behavior when they reach an abnormal range as they may in the aged. Birren (1963) considered this issue and developed the “discontinuity hypothesis.”
The discontinuity hypothesis is that individual differences in pyschological functions remain largely autonomous of somatic functions until critical or limit
ing levels are reached : e.g., as a consequence of disease or trauma, after which a new set of relationships holds. (Birren, 1963).
As long as physiological variables remain within “normal" limits they provide a necessary basis for functioning but not a sufficient or determining condition for behavior. Several lines of research provide evidence for the discontinuity hypothesis.
in an extensive biological and behavioral study of 47 healthy men over the age of 65, Birren et al. (1963) found that even in a group selected on the basis of outstanding health status there were subjects with mild asymptomatic disease. Correlations between psychological and physiological measurements were analyzed separately for two groups, a group of optimally healthy subjects and a group with mild asymptomatic disease. In the healthiest group only 5 behaviorphysiology correlations were statistically significant, while in the mild asymptomatic group 26 correlations were statistically significant. Birren (1963) interpreted these results in terms of the discontinuity hypothesis suggesting that some psychological variables are related to physiological variables only when the latter lie in an abnormal range.
Wilkie, Eisdorfer, and Nowlin (1972) also have evidence supporting the discontinuity hypothesis. Longitudinal data on the relationship between blood pressure and behavioral measures such as intelligence and reaction time suggested that only when blood pressure was elevated were there behavioral-blood pressure relationships. These data along with the data of Birren et al. (1963) suggest that some physiology-behavior relationships exist in old subjects which are not apparent earlier in the life-span, Hence, psychophysiological data collected early in the life-span do not always provide an exhaustive basis on which to predict behavior in the elderly. Concurrent physiological processes can be a significant source of variance.
Age functions in physiology and behavior : Fixed or variable ?-Life-span de. scriptive research has led to the demonstration that physiological efficiency declines with age, and psychophysiologists have accepted the biological decremental model so thoroughly and have been so preoccupied with relating behavioral changes to physiological decline that they have almost ignored behavioral and envoronmental influences on physiology. While psychophysiology involves the study of physiology-behavior relationships, the psychophysiology of aging has typically concentrated on the effect of physiology on behavior. In this sense, the psychophysiology of aging has to a great extent been unidirectional, attempting to explain changes in behavioral dependent variables in terms of changes in physiological independent variables. Few attempts have been made to consider age changes in physiology as a consequence of age changes in behavior or to attempt to manipulate physiological functioning by manipulating behavior. Recently, however, some attempts have been made to approach physiological age changes from a behavioral perspective.
Using a behavioral hypothesis to explain age changes in physiology, de Vries (1970) suggested that the change from an active to a sedentary life-style with age could be responsible for some of the observed age changes in physiological efficiency. DeVries (1970) hypothesized that much of the decline in physiological functioning such as in maximal oxygen consumption, work load tolerance, and muscle strength observed in the aged resulted from disuse rather than from ir. reversible biological decline, and he engaged healthy old men in an exercise program designed for the aged. With consistent participation and gradual increments in the exercise schedule these men were able to realize increased efficiency in the cardiovascular, pulmonary, and nervous systems.
Another attempt to influence physiological functioning with behavioral treatment was made by Woodruff (1972), who used an operant conditioning technique to train young and old subjpects to increase the production of brain waves faster and slower than the dominant brain wave frequency. Old subjects were able to learn as well as young subjects to increase the percentage time spent in brain wave frequencies two cycles per second faster and two cycles per second slower than the dominant brain wave rhythm, and this change in brain wave frequency affected reaction time. Both young and old subjects responded faster when they were producing fast brain waves and slower when they produced slow brain waves.
Taking a life-span perspective, psychophysiologists have accepted the notion that physiological decline, which begins to occur after the attainment of maturity, serves as a prologne for an invariable sequence of behavior change. The results of the work by de Vries (1970) and Woodruff (1972) suggest that this decremental model which has been derived from life-span studies has limited the perspec. tive of psychophysiologists who have assumed that age functions are fixed. In several respects the studies of de Vries and Woodruff imply that the past does not necessarily serve as a prologue for the future. First, behavioral intervention strategies were used to modify the behavior of old subjects so that they responded differently than they had in the past. In this manner their life-span pattern of behavior did not lock them into a single means of responding in old age. Second, the previous rate of lowered biological and behavioral efficiency did not preclude the realization of a more efficient rate. Third, the research of de Vries and Woodruff represents a break with past research in the psychophysiology of aging which indicated that behavioral and biological decline were irreversible. l'inally, the results suggest that the past mode of research in psychophysiology which has typically been descriptive need not set the pace for future research on the psycho physiology of aging which could also be aimed at modification and prevention as well as description.
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RELATIVE MERITS OF A LIFE-SPAN APPROACH : CONCLUDING PERSPECTIVES
It has been asserted that the life-span approach has been both useful and misleading in specific psychophysiological approaches to aging. To more generally delineate those circumstances in which the approach succeeds or fails, the effectiveness of the life-span model will be considered in terms of the research aims of description, explanation, modification, and prevention (see Baltes, this symposium).
Description.-It has been shown in the previous sections that research under. takes to describe physiological and behavioral changes over the life-span has been a major thrust in gerontology for the past 25 years. Accurate description of changes over the life-span has not been an easy task, and developmentalists have identified numerous sources of bias in life-span descriptive research and have suggested that a large number of controls are required to ensure the collection of accurate life-span data (e.g., Baltes, 1968; Birren, 1959; Nesselroade & Reese, 1973; Schaie, 1965; Wohwill, 1970). Since it is so troublesome to gather unbiased data describing ontogeny, one must assume that the usefulness of such information has justified the effort. Life-span descriptive psychophysiological data are useful as a first step toward the explanation, prediction, and prevention of behavioral changes in old age inasmuch as they can lead to the identification of variables influencing behavior in old age.
The work of Surwillo (for summary, see Surwillo, 1968), provides an example of the usefulness of the life-span descriptive approach in the psychophysiological study of aging. The descriptive literature on the life-span contained ample evi. dence that reaction time and the frequency of the EEG alpha rhythm followed similar developmental patterns. Surwillo (1963) attempted to determine if these variables were related, and by simultaneously measuring reactiou time and EEG alpha frequency he found a high correlation between the two variables. These results led Surwillo to hypothesize that the slowing of the dominant EEG frequency might be responsible for the slowing of reaction time with age.
The description of physiology-behavior relationships is a useful first step in the generation of hypotheses about behavior in old age, but all too often the life-span descriptive approach has represented the end product of developmental research. Great bodies of descriptive data have been collected, but few attempts have been made to weave such data into theories of behavioral aging or to test hypotheses experimentally which might be generated from descriptive research. Indeed, Surwillo (1963) is one of the few investigators who have used the life-span data to devise a specifically stated hypothesis about the physiological causes of behavior change with age. The life-span descriptive approach succeeds when it is used for its hypothesis generating value, but it fails when it is seen as an end in itself.
Erplanation.-In some but not all instances the life-span approach provides useful information for the explanation of behavior in aging. It has been suggested previously that the rate of change in a given physiological variable affects the degree to which behavior is involved, with changes taking place over a short period of time causing greater behaviorial involvement than changes which are spread over the life-span. Concurrent information on physiology-behavior relationships in the aged provides no insight on how the variables reached the cur. rent level of functioning. For this reason life-span data are essential in explaining and predicting behavior in old age.