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Ann. Rev. Psychol. 1978. 29:373-404

Copyright © 1978 by Annual Reviews Inc. All rights reserved

BIOFEEDBACK AND

Annu. Rev. Psychol. 1978.29:373-404. Downloaded from www.annualreviews.org by Glasgow University on 05/15/13. For personal use only.

VISCERAL LEARNING Neal E. Miller The Rockefeller University, New York, NY 10021

INTRODUCTION What is Biofeedback? In instrumental learning (also called trial-and-error learning or operant condition­ ing), whether a response is learned and performed depends on whether that response is followed by a reward or by a punishment. When a novice is learning better voluntary control over where the ball goes in shooting fouls, seeing the ball go through the hoop (success) serves as a reward, and seeing it miss (failure) serves as a punishment. If a novice were blindfolded so that he did not have any knowledge of the results of his shots, he would not learn. Rewards, punishments, and knowl­ edge of results have been called feedback. Most people are poor at correctly perceiving their visceral responses, such as blood pressure, and some people with tension or neuromuscular disorders are poor at perceiving feedback from certain skeletal muscles. They are like a blindfolded novice trying to learn to shoot baskets. Modern measuring devices can remove the blindfold by supplying better feedback. Feedback provided by a device that provides prompt measurement of a biological function has been called biofeedback. It should be useful for any learnable response the acquisition of which is impeded by poor or erroneous perception of the correct response

(137). Biofeedback can be used also to

help animals and people to learn to improve the perception of certain visceral events

(1). Such learned perception in patients sometimes can eliminate the need for assistance from the biofeedback instrument (138). An attractive feature of biofeed­ back is that it teaches the patient to do something for himself. Biofeedback is part of a larger new area of research called behavioral medicine. Previously, behavioral science has been related primarily to one branch of medicine, psychiatry; now it is becoming related to the rest of medicine

(140, 147,210). One

of the important areas of behavioral medicine is the effects of stress on psy­ chosomatic symptoms, on the immune system, and on a wide range of diseases and disorders (141). By emphasizing the measurement of and the production of changes in bodily processes, biofeedback is contributing to the applications to medicine of other behavioral techniques for relief from stress, such as transcendental meditation 373

0066-4308/78/0201-0373$01.00

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and the relaxation response (14). The work on biofeedback also is a part of a larger development of increased understanding of the role of learning in a variety of homeostatic processes ( 1 42). In fact, one of the early reports on the instrumental learning of visceral responses and of changes in the EEG (brain waves) was entitled "Extending the Domain of Learning" ( 1 35). Unfortunately, biofeedback has been greatly exaggerated by the public media; much more research is needed to improve the learning, to determine what type of effect is learned, and to evaluate possible therapeutic applications. Annu. Rev. Psychol. 1978.29:373-404. Downloaded from www.annualreviews.org by Glasgow University on 05/15/13. For personal use only.

Overview The key scientific issues in this chapter are (a) What visceral and other responses believed to be unmodifiable can be modified by instrumental training procedures? (b) Where such modification is possible, what is the type of learned effect involved -direct or indirect? (c) What are the laws, i.,e. significant parameters, governing the learned modification of such responses? In evaluating the possible therapeutic effects of biofeedback, the key problems are (a) to compare it with the best currently available forms of treatment for specific condiitions and types of patients, and (b) to determine the extent to which its effects are placebo ones. Even where biofeedback is presently poorer than other available treatments, if its effects are genuine, they may possibly be gready improved by discovering more about the laws governing this type of learning and performance; but if its effiects are solely placebo ones, such an effort will be pointless. Adapting the procedure used for evaluating drugs ( 1 87), three general phases may be described: 1 . Pilot studies to determine whether there acre any promising effects worthy of investigation, and to detect any bad side effects or practical difficulties. These may be anecdotal case reports, systematic case studies, or uncontrolled single group studies (2 1). 2. Controlled comparisons with the best available other techniques or with placebo treatments, using somewhat larger groups of patients carefully studied, ideally with double-blind procedures, and adequately followed up. 3. Broad clinical trials on large samples und,er the conditions to be expected in general use, to determine the effectiveness of the treatment in other than unusu­ ally favorable experimental conditions with especially talented and enthusiastic therapists. Almost all of the therapeutic applications of biofeedback are in exploratory Phase I. Recently some studies approaching the standards of Phase 2 are beginning to appear, but the number of patients is still too small for any definitive conclusions. Thus the therapeutic effectiveness of biofeedback is not yet definitely proved. There is much more need for the mundane task of rigorously evaluating the most promis­ ing of the current therapeutic applications than for the exciting adventure of trying to devise ingenious new ones. We need studies in which different investigators agree to cooperate to secure comparable data in a reasonable time on an adequate number of patients.

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WHAT VISCERAL RESPONSES CAN BE AFFECTED BY INSTRUMENTAL TRAINING?

After early studies by Tarchanoff in 1 885 (20 1), there have been a considerable number of clinical reports of voluntary control over heart rate, dilation of the pupils, and piloerection ( 1 09, 1 27, 1 34, 1 57). Nevertheless, on the basis of an assertion by Miller and Konorski in 1 928 ( 1 48) and two exploratory experiments incompletely reported by Skinner in 1 938 ( 1 9 1 ) and Mowrer in 1947 ( 1 50), it was concluded that visceral responses mediated by the autonomic nervous system are not subject to instrumental learning, and virtually no work was done until the late 1 960s ( 1 08, 1 36) -a tribute to the strong prejudice in our culture against the autonomic nervous system and the visceral responses that it controls ( 1 37).

Experiments on Normal Human Subjects Kimmel, who was a pioneer, has summarized experiments showing that instrumen­ tal learning can be used to train human subjects to control visceral responses in one 'way or another (108). Most of the studies on biofeedback are collected in a series of reprint annuals (7-9, 55, 102, 143, 1 88, 1 99). Studies in these summaries show that instrumental training can produce both increases and decreases in vasomotor responses, the galvanic skin response, heart rate and rhythm, blood pressure, saliva­ tion, and possibly gastrointestinal motility (142). In each of these functions, except the last one, learned changes have been repeatedly confirmed. The chief controversy concerns which of the various types of learned effects to be described under the next major heading has been produced (52, 58, 104, 108, 1 76).

Experiments on Normal Animals Experiments on modifying visceral responses by instrumental learning in normal animals have been summarized by Harris & Brady (93). The first full-scale experi­ ment, by Miller & Carmona (144), showed that during 40 days of I-hr daily sessions thirsty dogs rewarded by water for salivating increased their rate reliably while those rewarded for not salivating decreased it reliably, producing a 14-fold difference between the two groups. Such learning has been confirmed by Shapiro & Herendeen ( 1 89), using food as a reward to decrease salivation, a change opposite to what would be expected from classical conditioning. Other experiments have trained bidirec­ tional changes in the heart rate of rats (56) and monkeys (64), while large increases have been taught to baboons (95). With blood pressure, bidirectional changes have been produced in rats ( 1 6 1 ) and in monkeys ( 1 5). The most impressive results are those by Harris et al (96), using punishment for wrong responses and reward for correct ones to train baboons to maintain a 30 mm Hg increase in blood pressure over a l 2-hr period of time. Although two control baboons reinforced for reduction in blood pressure, and actually receiving more electric shocks, did not lower it, they did not increase it, so that there was a large difference between the two groups rewarded for different changes. The foregoing results, replicated in a number of laboratories with normal animals, strongly support the human ones; they also provide a greater opportunity to investi-

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gate the physiological mechanisms and the psychosomatic effects of these changes produced by learning. But they do not yield (:vidence on which of the various types of learned effects were produced.

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Experiments on Rats Paralyzed by Curare To control for the possible effects of overt muscular activity on visceral responses, experiments (93, 1 37) were conducted in the author's laboratory on rats paralyzed by curare and artificially respirated. At first these experiments were confirmed by results in three other laboratories (6, 30, 1 92), but later the results of apparently similar experiments progressively declined until it became impossible to repeat them in spite of extensive efforts in the author's laboratory (57, 58, 145) and elsewhere (28, 1 76; DiCara, personal communication). Attempting to discover the cause and correct this baffling decline, Dr. Dworkin and I have tested unsuccessfully many possibilities and made several major and many minor improvements in the technique of respirating animals paralyzed by curariform drugs, so that they can now be maintained in excellent condition for approximately 6 days (57, 58, 145). In addition to the extensive failures cited above, a few recent reports of positive results have appeared (4 1 , 65, 2 1 6). It is not clear that any of these recent studies used the essential control of making all of the adjustments in respiration, tempera­ ture, etc before determining the direction of training and no changes thereafter. The ones on rats have not used the much better-controlled endotracheal catheter (58) for respiration. Therefore, in the face of the much more extensive, careful studies that have failed to replicate the results of the original ones, it is prudent not to rely on any of the experiments on curarized animals for evidence on the instrumental learning of visceral responses. VARIOUS TYPES OF LEARNED EFFECTS

In any experiment on learned modification of visceral responses, either by classical conditioning or by instrumental training, there are various ways that an effect may be produced (58). Many of the current controversies concern the following effects (52, 5 8, 104, 108, 1 76).

Skeletal Response Produces Mechanical Artifact This effect involves no visceral learning but is merely an artifact. A learned skeletal response may have a direct mechanical effect on the transducer used to measure the visceral response. For example, contractions of the abdominal muscles or of the diaphragm that are not visibly obvious can produce pressure changes in the intestine that easily may be mistaken for intestinal contractions, particularly if they are observed with a single catheter tip ( 1 42). In photoelectrically recording blood vol­ ume in an artery, a movement of the skin may change the position of the transducer and hence produce an artifact. The need to guard against subtle sources of artifact is much greater in experiments on the effects of learning than it "is in many other psychophysiological applications because if it is easier for the subject to produce the artifact than to control the response, he is likely to learn to do so, often uncon-

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sciously. Exactly the same thing is true for the mechanical effects and the visceral reflexes described under the next two headings.

Skeletal Response Produces Mechanical Effect learned skeletal response may produce a purely mechanical or physical effect on a visceral process. For example, some of the Yogis who claim to be able to stop their hearts for brief periods of time perform an exaggerated Valsalva maneuver that builds up sufficient pressure in the thoracic cavity to shut off the return of blood via the veins to the heart. This effect is so physiologically significant that it can be maintained only for a short while. It stops the pulse and, since heart sounds are produced by the action of the blood on the valves, stops them as heard by stetho­ scope, but an ECG proves the heart is beating faster than normal (3). Slightly cupping one hand and spreading the fingers of the other one produces a temperature difference between the two hands. Contractions of abdominal muscles mechanically facilitate regurgitation or passing a stool (142). With EEG electrodes placed in a temporal position, eye movements produce a large change in the electrical field which blocks the ordinary amplifier, eliminating the alpha rhythm for a few seconds (92).

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A

Skeletal Response Stimulates Visceral Reflex learned response, or the metabolites of the muscular activity involved, can stimu­ late the receptive field of an innate visceral reflex and thus elicit a visceral response. A crude example is putting a finger down the throat to elicit vomiting. Cardiovascu­ lar responses are especially susceptible; o. A. Smith ( 195) gives an excellent review of the pertinent physiology. The blood flow to a specific limb is increased by its muscular activity (60, 1 30). Heart rate and blood pressure can be increased by isometric muscular contractions not always easy to detect ( 1 3 1). Similarly, freely moving rats rewarded for increasing their heart rate consume more oxygen, presum­ ably indicating more muscular activity, than those trained to decrease it (3 1). Heart rate is sensitive to any change in breathing which changes the pC02 level of the blood (58). Several investigators have shown that when human subjects are re­ warded for changing their heart rate, they change their breathing and/or muscular tension, and that the better such changes are controlled, the smaller the learned changes in heart rate become ( 1 26, 1 55). One of the best controls of respiration was achieved by VanDercar et al (204), who habituated human subjects to the use of artificial respiration via a face mask and found no remaining learned control of heart rate that was not accompanied by changes in the electromyograph (EMG). On the other hand, Pickering et al (166) used spirometer tests to show that patients severely paralyzed by polio or muscular dystrophy could perform instru­ mentally learned changes in blood pressure without changes in the tracings of respiratory activity or in the pC02 level of expired air. They also did not show any changes in EMG activity in the limited nonparalyzed musculature. Brucker (33) has shown that two patients paralyzed by lesions between C3 and C4 and between C4 and C5 in the neck can learn to produce, without consistent changes in respiration or in EMG activity of their limited musculature, increases in systolic blood pressure A

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that are larger than those produced by far greater instructed changes in respiration or in muscular contraction. While it is barely conceivable that the contingencies of rewarded training selected out an inconspicuous combination of skeletal responses that was more effective than the large ones that the subjects were instructed to make, this has not been demonstrated to be possible. Other visceral responses can be elicited by skeletal ones. A galvanic skin response (GSR) recorded from one hand can be produced by flexing the muscles of the contralateral hand or the ipsilateral foot (53). Urination can be elicited by using abdominal muscles to increase pressure on the partially filled bladder until stimula­ tion of stretch receptors elicits reflex emptying. While all of the foregoing skeletally mediat(�d reflexes are genuine learned effects, none of them indicates learning by the autonomic nervous system; all of them are dependent on a unique anatomical relationship that allows a specific visceral re­ sponse to stimulate a specific receptive field (58). Nevertheless, such indirect effects of learning may be highly significant in eith(�r the etiology or therapy of visceral symptoms. Certain hysterical patients produce the symptom of tachycardia by hyperventilation, which lowers the pC02 level of the blood and stimulates receptors for cardiovascular reflexes increasing heart rate ( 1 65). In one case, attacks of paroxysmal bigeminy (premature ventricular contractions alternating with normal heart beats) were elicited by Valsalva maneuvers and terminated by exercise that speeded up the heart rate ( 1 67). Some patients can arrest an attack of paroxysmal tachycardia by the vagal reflex elicited by taking a sudden deep breath and others by plunging their face in cold water.

Centrally Integrated Skeletal- Visceral Pattern Both skeletal and visceral responses may be inextricably linked together as parts of a centrally integrated pattern that can be elicited by learning. Obrist et al ( 1 56) and Roberts ( 1 76) have summarized experimental work on cardiovascular patterns of this kind and have pointed out the useful physiological functions that they serve; O. A. Smith ( 1 95) summarizes pertinent neurophysiology. But to prove that such a pattern really is central, it is necessary to rule out the possibilities discussed under the three preceding headings. This has been done in a few experiments on cardiovas­ cular responses. For example, K. Smith (193) maintained the extreme position that all classically conditioned visceral responses are produced in one of the ways de­ scribed under these headings and that the autonomic nervous system is totally uneducable. By summarizing evidence that classical conditioning of heart rate can occur in dogs completely paralyzed by curare, Black & Lang ( 1 7) forced Smith ( 1 94) to retreat to a position of centrally integrated skeletal-visceral patterns. To return to instrumental learning, Goesling & Brener (85) have trained some rats to be active and others to be immobile and shown that this affects their heart rate when tested later under paralysis by curare. Freyschuss (76) showed that attempts to contract an arm, the motor nerve to which was paralyzed by a local anesthetic, produced an increase in heart rate and in blood pressure; and Pickering et al ( 1 66) showed that increases in heart rate and blood. pressure are produced when patients try to squeeze a cuff with the hand of an arm that is completely paralyzed by polio

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or muscular dystrophy. Lapides et al ( 123) proved that the performance of skeletal maneuvers is not essential for the control of urination by an experiment showing that human subjects with their skeletal muscles completely paralyzed by either curare or succinylcholine can both initiate and terminate urination upon command. Results of this kind demonstrate genuine ability of the central connections of the autonomic nervous system to be modified by learning. Showing that a command to a skeletal muscle is sufficient for eliciting a visceral response, however, does not prove that it is necessary.

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Elicitation of Independent Visceral Response A visceral response may be learned that can be elicited without any necessary skeletal links. Many skeletal responses occur as part of a centrally integrated pattern involving other skeletal responses, but they are not inextricably linked together; with sufficient practice they can be made highly specific or organized into new patterns. The question is, do visceral responses have at least some of this ability to become more specific and to be integrated into new patterns (1 37)? In the most limited case, a given visceral response would always have to be a part of the same centrally organized skeletal-visceral pattern. At the other extreme, a visceral response could be elicited without central linkage to any skeletal response. Obrist et al (1 56) have summarized evidence suggesting that uncoupling of cardiac and skeletal responses may occur in situations involving strong sympathetic activity. Lacey & Lacey ( 1 1 7) summarize evidence that it can occur with shifts in attention. In an intermediate case, the same visceral response could be elicited as part of a number of different centrally integrated patterns (48). At least this last amount of flexibility is proved by the patients paralyzed by polio or muscular dystrophy. When they learned instrumentally to increase their blood pressure, most of them did so without changing their heart rate. Thus they did not achieve this elevation as part of a central pattern involving a command to tense their paralyzed muscles, which produces an increase in both blood pressure and heart rate ( 1 66). We already have seen that Brucker's patients paralyzed from the neck down did not use the overt performance of skeletal responses to stimulate a receptive field that elevated their blood pressure. The most probable central pattern of skeletal-visceral responses that would produce a prompt rise in blood pressure would be the com­ mand to contract all of their muscles. A request to try as hard as possible to contract all of their intact and paralyzed muscles produced obvious signs of intense effort but it did not produce as great an increase in systolic pressure as did a request to produce the learned increase, which was performed without any signs of effort (33). Al­ though it is conceivable that some as yet undiscovered central-visceral pattern could have produced the learned increase in blood pressure, the results argue for a learned, independent elicitation of a visceral response. It can be seen that the problem of determining which type of visceral effect the learning has produced is far from simple. But as the issues are becoming more clearly defined, well-controlled experiments directly aimed at producing learned modifications in appropriately selected, specific skeletal-visceral patterns are likely

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to produce significant increases in our understanding of the ways that learning can be involved in homeostatic processes vital to health (58, 1 37).

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SPECIFICITY AND FLEXIBLE PATTERNING OF LEARNED VISCERAL RESPONSES

In addition to being relevant to the foregoing issues, work on the learned specificity and flexible patterning of different visceral responses is significant in its own right. We have seen that polio patients learned to change their diastolic blood pressure without changing their heart rate ( 1 66). Studi

Biofeedback and visceral learning.

ANNUAL REVIEWS Further Quick links to online content Ann. Rev. Psychol. 1978. 29:373-404 Copyright © 1978 by Annual Reviews Inc. All rights reserv...
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