ANNOTATlONS

AUGMENTED FEEDBACK TRAINING OF MOTOR CONTROL IN CEREBRAL PALSY

AUGMENTED feedback training involves providing a person with additional data about his performance of motor tasks, so that he is in no doubt as to what modifications are necessary or when improvements are achieved. Many types of augmented feedback exist'. Faced with the problem of teaching a child to write, the experimenter may opt to provide a moment by moment check of where the pen is in relation to where it should be (continuous feedback), or he may let the child finish forming a letter before he criticises its execution (knowledge of results). Movements are not, however, always judged in terms of their functional utility (task feedback). Sometimes the emphasis is on motor control per se, with patients being taught how to regulate muscular ccntractions and interpret sensory events. Ir . such cases biofeedback would be used.

Amongst the patients who should benefit from augmented feedback are those who have failed to improve because they lack an adequate understanding of what the task involves, and those who have been prevented by sensory deficits2-10 from achieving greater skills. Whether improvements are achieved during training depends on the appropriateness of the feedback provided. It would be wrong always to give the most precise data possible; sometimes subjects would find its nuances unintelligible, and some- times they would have to concentrate so hard on processing the information as to be actually prevented from experimenting with ways of improving their motor control. Whilst augmented feedback should offset the ignorances of the patient, there may have to be a gradual build-up of detail so that he can always readily cope with the data presented.

In the case of patients with sensory deficits, improvements will be permanent only when these problems are overcome during training. A number of the deficits shown by cerebral- palsied patients are probably remediable. Cerebral-palsied neuromusculatures function in such complex ways that it is not surprising if individuals fail to discover the significance of certain sensory discharges". Some types of afferent output are known to be abnormal, and for this reason possibly more difficult to categorise'l- 12. Moreover, on the basis of signal detection theory, JONES'~ argues that cerebral-palsied individuals will sometimes be unaware of movement cues because of the abundance of other sensory impulses present. Augmented feedback should help by highlighting appropriate natural (intrinsic) movement signals and by providing the patient with a guide for reclassifying intrinsic feedback. A variety of movement cues are used by neurologically normal individual~~~'1~. Some provide information about efferent programming; others allow the person to assess the progress and appropriateness of actions. The permanent benefits of training depend on which cues are discovered, but no amount of feedback experience will help if substitute intrinsic cues do not exist''.

The question whether to choose continuous feedback or knowledge of results is an important one. At first sight, it might seem best to have augmented and intrinsic feedbacks simultaneously present, so that the patient can immediately compare the two. The process- ing of augmented feedback may require so much attention, however, that the patient is prevented from discovering intrinsic movement signals. Moreover, HER MAN'^ points out that, in the case of patients with central neurological lesions, neural discharges are probably distorted in space and time. If this is so, introducing continuous feedback may aggravate the distortion problem and lessen the chances that natural cues will be discovered. HERMAN

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DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY. 1977, 19

also claims that patients with a central lesion are prone to showing improvements which they lose when augmented feedback is removed. This should not happen when know- ledge of results is used; for patients will only show improvements during training if they are able to initiate appropriate sequences of movement and detect and correct errors. It is Fossible that continuous feedback not only makes the discovery of intrinsic cues more difficult but actively encourages a dependence on augmented feedback and a strategy of continuously correcting performances.

Vcry few cases of augmented feedback training have involved cerebral-palsied patients. Task feedback was used by SACHS and MAYHALL to reduce ‘involuntary’ body movements1* and when teaching an athetoid adult to track a moving object with a penlg. Using this approach, SACHS and co-workersZ0 taught a deaf, quadriplegic athetoid child to produce sequences of finger movements, and SPEARING and POP PEN^^ reduced foot dragging in an athetoid student. Whilst the improvements reported are impressive, these are all single-case studies and offer little indication of what skills could be taught in this way or which patients should benefit.

Biofeedback therapy has been used to treat a variety of neuromuscular disorders. Patients have been taught to contract reinnervated musclesZ2, reduce hyper t~nic i ty~~ and overcome muscular weakness24-26. In many instances, lasting improvements are reported”, but this approach has seldom been tried with cerebral-palsied patients. BRUDNY and colleagues2* claim excellent improvements in hand function after providing a patient with electro- myographic feedback from spastic muscles, but unfortunately they do not detail the train- ing given. Our own studies have shown that, under laboratory conditions, spastic adults can be taught to reduce hypertonicity, relax more quickly, maintain tension levels more precisely and classify muscular activity more appropriately when electromyographic feed- back is given. Patients also learned to execute set patterns of activity in one and two muscle groups”. 29* 30. It remains to be seen, however, whether they can also achieve normal precision when more complex tasks are set.

A proper assessment of the therapeutic value of augmented feedback training for cerebral- palsied individuals must await a systematic investigation into which of the many problems presented by this syndrome (e.g. hyperreflexia, hypertonicity, reflex radiation, antagonist interaction, muscular weakness, sensory deficit and poor motor programming) respond to training. Biofeedback studies should enable these questions to be answered ; but this type of feedback is unlikely ever to be used clinically, except where information from a limited set of muscles would suffice. Providing an electromyographic definition of an action such as eating would involve a multitude of physiological recordings, and patients would probably find it impossible to interpret the vast amount of data presented. The proper r6le of biofeedback probably lies in helping the clinician diagnose why patients are unable to perform actions more skilfully, and in teaching patients to rectify abnormal patterns of movement, eliminate unwanted reflexes, regulate contractions and interpret sensory data. Armed with this new understanding, the pdtient will probably build up better patterns of movement. Task feedback is a powerful tool for helping him to do so; but the therapist must be clear what the aim of training is. Teaching a cerebral-palsied person to produce more normal movement sequences is sometimes antithetical to making him more skilful3’: the fastest, most economic and accurate way for him to perform a task may involve highly idiosyncratic patterns of movement. Promising as the results to date are, it is vital that augmented feedback therapy should not be used prematurely,

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ANNOTATIONS

otherwise it may fall into disrepute simply because unsuitable patients are treated and unrealistic therapeutic goals are set.

Department of Psychology, University of Sheffield, Sheffield SIO 2TN

ANN HARRISON

AcX/ r~Jrc~ l r~~ l~ i~r? imt : The author is supported by a grant from the National Fund for Research into Crippling Diseases. which is gratefully acknowledged.

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REFERENCES Annett, J. ( 1969) Fcwlback and Human Behaviaur. Harmondsworth, Mddx. : Penguin Books. Tizard. J. P. M.. Crothers. R. (1952) ‘Sensory disturbances in hemiplegia in childhood.’ Transnrtims of

the Ariierican Neurological A.wx-iation, 77,227. Kabat, H., Knott, M. (1953) ’Proprioceptive facilitation technique for treatment of paralysis.’ Physical

Therapv Review, 33, 53. Tizard, J. P. M., Paine, R . S., Crothers, 5. (1954) ’Disturbances of sensation in children with hemi-

plegia.’Jorrrna/ o/’thv Americrm Medicul,4ssoricr/ion, 155,628. Rood, M. S. (1954) ’Neurophysiological reactions as a basis for physical therapy.’ Ph.vsira1 Therapy

Review, 34,444. Hohman, L. B.. Baker, L., Reed. R. (1958) ‘Sensory disttirbances in infantile hemiplegia, triplegia, and

quadriplegia. ’ American Journal of’ Ph-vsical Medicine, 37, I . Skatvedt. M. (1960) ‘Sensory, perceptual and other non-motor defects in cerebral palsy.’ I n Mac

Keith, R., Bax, M. (Eds.) Child Neurology andCerehra1 Palsy. Little Club Clinics in Developmental Medicine No. 2. London: Medical Advisory Committee of the National Spastics Society in associa- tion with Heinemann Medical Rooks.

Abercrombie. M. L. J. (!964) Perceptual and Vi.suonrotor Disorders in Cerebral Palsy. Clinics in De- velopmental Medicine No. 1 I . London: S.I.M.P. with Heinemann Meaical.

McDonald, E. T., Chance, B. (1964) Cerebral Palsy. Englewood Cliffs, N. J.: Prentice-Hall. Bobath, K. (1971) ‘The normal postural reflex mechanism and its deviation in children with cerebral

palsy.’Physiotherapy, 57,5 15. Harrison, A. (1975) ‘Components of neuromuscular control.’ In Holt, K. S. (Ed.) Movemerrt and Child

Devr/oon:ent. Clinics in DeveloDmentaI Medicine No. 55. London: S.I.M.P. with Heinemann Mcdical.

Harrison, A., Connolly, K. (1971) ‘The conscious control of fine levels of nueromuscular firing in spastic and normal subjects.’ Developmental Medicine and Child Neurolog.v, 13,762.

Jones. B. (1976) ’The perception of passive joint movements by ccrebral palsied children.’ Develop- mental Medicine and Child Neurology, 18,25.

Rossom, J. (1974) ‘Movement without proprioceptton.’ Brain Research, 71,289. Connolly, K. (1969) ‘Sensory-motor coordination: mechanisms and plans.’ I n Wolff, P. H.. Mac Keith

R. (Eds.) Planning for Betrer Learning. Clinics in Developmental Medicine No. 33. London: S.I.M.P. with Heinemann Medical.

Herman, R. (1973) ’Augmented sensory feedback in the control of limb movement.’ I n Field, W. S. (Ed.) Neurol OrRanization ond its Relevanrc to Prosthetics. New York: I.M.B.C.

Brenner, J . ( 1973) ’Factors influencing the specificity of voluntary cardiovascular control.’ I n Di Cara, L. V. (Ed.) The Limbic and Autonomic Nervous Systems: Advances in Research. New York: Plenum.

Sachs, D. A., Mayhall, B. (1971) ‘Behavioral control of spasms using aversive conditioning with a cerebral palsied adult.’JoirrnaloJNervous and M e n d Disease, 152,362.

Sachs, D. A., Mayhall, B. (1972) ’The effects of reinforcement contingencies upon pursuit rotor per- formance by a cerebral palsied adult.’JournalofNervorrs and Mental Disease, 155.36.

Sachs, D. A., Martin, J. E., Fitch, J. L. (1972) ‘The,effect of visual feedback on a digital exercise in a functionally deaf cerebral palsied child.’ Journal of Behavioural Therap,y and Experimental Psychiatry, 3, 217.

Spearing, D. L., Poppen, R. (1974) ‘The use of feedback in the reduction of feet dragging in a cerebral palsied client.’Journulof’ Nr,rvcw.vand Mental DLvose, 159, 148.

Booker, H. E., Rubow. R. T.. Coleman, P. J. (1969) ‘Simplified feedback in neuromuscular retraining: an automattd approach using electromyographic signals.’ Archives of Physical Medicine and Re- lrobiliration, 50, 62 I .

Netsell, R., Cleeland, C. S. (1973) ‘Modification of lip hypertonia in dysarthria using EMG feedback.’ Jotrrnalof’Speech and Hearing Disorderv, 38, I3 I .

Marinacci. A. A., Horande, M. ( 1960) ‘Electrornyogram in neuromuscular re-education.’ Bulletin of the 1-0s Angeles Niwrdogicui Soeie ty ,25, 57.

Andrews, J. M. (1964) ‘Neuromuscular reeducation of the hemiplegic with the aid of the electromyo- graph.’ Archives of’Phy.vical Medicine and Rehabilitation, 45,530.

Johnson. H. E.. Garton, W. H. (1973) ‘Muscle re-education in hemiplegia by use of electromyographic device.’ Arzhiws of Ph.rsical Medicine ond Rehahilitotion, 54, 320.

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27. Blanchard, E. B., Young, L. D., Jackson, M. S. (1974) ‘Clinical applications of biofeedback training.’ Archives of General Psychiatry, 30, 573.

28. Brudney, J., Korein, J., Levidow. L., Grynbaum, B. B., Lieberman, A., Friedmann, L. W. (1974) ‘Sensory feedback therapy as a modality of treatment in central nervous systen disorders of volun- tary movement.’ Neurology, 24,925.

29. Harrison, A. (1975) ‘Studies of neuromuscular control in normal and spastic individuals.’ In Holt, K . S. (Ed.) Movement and Child Development. Clinics in Developmental Medicine No. 55. London: S.I.M.P. with Heinemann Medical.

30. Harrison, A. (1975) ‘Training spastic individuals to achieve better neuromuscular control using elec- tromyographic feedback.’ In Holt, K. S. (Ed.) Movement and Child Development. Clinics in Develop- mental Medicine No. 55. London: S.I.M.P. with Heinemann Medical.

31. Connolly, K., Harrison, A. (1975) ‘The analysis of skill and its implications for training the handicap- ped.’ In Siva Sankar, D. \. (Ed.) Psychiatric and Psychological Problems in Childhood. Oakdale: P. J . D. Publications.

PREDICTION OF ADULT STATURE THE adult height of a child is largely determined by the stature of his two parents, but is also affected by how long he grows and at what rate. These factors are at least in part environmentally determined and the length of the growing period-or at least the amount of growth that has passed-is reasonably reflected in the child’s skeletal maturity. Accord- ingly it is possible to use measurements of stature and of bone age in a child to predict his adult height.

One may justifiably ask why there is any reason to try to predict adult stature and, were it not for man’s insatiable curiosity about his future, there would in truth be little point since, apart from frustrating the intentions of nature, man cannot “by taking thought add one cubit to his stature”’. Doctors can, of course, treat an abnormal condition and make the most of their patients’ genetic statural potential, but this has nothing to do with the business of height prediction.

There are three indications for predicting adult stature. The first is for curious parents to find out how tall their children are going to be, which may be important to them for vocational reasons if, for example, the child wishes to become a ballet dancer or a police officer. The second is for the anxious (and often tall) parents of a tall child who wish their child to be spared the embarrassment of being too tall. Androgens and oestrogens given in this situation speed up growth in height, but they advance skeletal maturation more quickly than they cause growth in height and the consequence is a diminution of the final height attained. The third reason is for the child whose growth and pubertal development are delayed: the physician may wish to know what the growth prognosis is likely to be so that he can assess whether to use androgens or oestrogens in order to induce puberty con- temporaneously with the child’s peers. Pubertal delay is seldom so extreme as to warrant this form of treatment, with its iatrogenic consequences on final stature, but the considerable anguish of a child with pubertal delay must not be underestimated.

From the medical point of view, the problem is that height-prediction equations are valid only for children who fall within the same limits for height and skeletal maturation as the standardizing group. They should not be extrapolated without extreme caution to predict the heights of tall or short children, whose growth is unusually advanced or retarded. It could be claimed, therefore, that statistically they are of very limited value to the practising clinician: nevertheless they do provide him with information which cannot be obtained otherwise and which is not much more imperfect than other information on which he depends for making clinical decisions.

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