Monosynaptic reflexes flexors manJouirnalofNeuirology, Neluroslurgery, andPsychiatry, 1976, 39, 555-565 Monosynapticreflexes in the superficial forearm flexors in manandtheir clinical

Jouirnal of Neuirology, Neluroslurgery, and Psychiatry, 1976, 39, 555-565

Monosynaptic reflexes in the superficial forearmflexors in man and their clinical significance

JACQUES DESCHUYTERE1, NOEL ROSSELLE, ANDCONSTANT DE KEYSER

From the Centre ofElectromyography and Electrodiagnosis, Kliniek Heilige Familie, Antwerp,and the Department ofEMG and Clinical Neurophysiology, University ofLouvain, Louvain, Belgiunm

SY N OP S I S Indirect motor responses with the characteristics of the H wave were recorded from theflexor carpi radialis and the palmaris longus muscles in normal adults. A series of experiments hasbeen performed, constituting circumstantial arguments for the monosynaptic nature of these reflexresponses. The findings in pathological conditions, which corroborated this point of view, aredocumented briefly.

H reflexes have been studied extensively in manand it seems certain that group I nerve fibressubserve the monosynaptic reflex arc for thetendon tap as well as for the response evoked bysubmaximal electrical stimulation of the mixednerve (Magladery et al., 1951). At variance withthe postulations of Magladery et al. (1951), itwas shown by Mayer and Feldman (1967) thatF waves were consistent with recurrent dis-charges. However, these authors stressed that, inthe normal subject, the F response consisted of amore complex potential and, with careful testing,that the H wave could be distinguished from theF wave. Employing special techniques offacilitation, genuine monosynaptic reflex activitywas demonstrated in the anterolateral muscles ofthe leg in normal adults by Deschuytere andRosselle (1971), and measurements of thelatencies of the reflex activity in the extensordigitorum longus muscle appeared to be veryuseful in studies of chronic fifth lumbar rootcompression syndromes (Deschuytere andRosselle, 1973).The present paper will document formerly

presented (Deschuytere and Rosselle, 1974) andnew arguments for the point of view that theindirect motor responses derived from the1 Address for correspondence and reprints: Dr J. Deschuytere,Provinciale steenweg 89, 2621 Schelle (Antwerp), Belgium.(Accepted 18 Februiary 1976.)

forearm flexor muscles may be considered asmonosynaptic reflexes. Their clinical use(Deschuytere and Rosselle, 1975) is primarilyconcerned with measurements of latencies andthe study of sinusoidal vibration of the tendon inrespect of hyperreflexia.

METHODS

We examined 50 healthy adults, aged 18 to 64 years,who were without history or signs of neurologicaldisease. The subjects lay in a supine position on acomfortable couch with the arm slightly abductedand with the elbow joint conveniently positioned at350 flexion. At times the hand was fixed firmly bytape to ensure isometric contraction. Reinforcementmanoeuvres consisted ofipsilateral quadriceps musclecontractions, either isometric or with raising the leg(15 subjects). Electromyographic recording wascarried out by coaxial needle electrodes inserted intothe flexor carpi radialis muscle (20 subjects on bothsides) and palmaris longus muscle. Electricalstimulation was performed either with bipolar surfaceelectrodes or by a modified Simon electrode (Simon,1962); in some individuals needle electrodes wereused as well. Rectangular electric pulses of 1.0 msduration were delivered by a stimulus isolation unitat a chosen strength. The median nerve was stimulatedin the cubital fossa and in some subjects at the levelof the axilla to prove the spinal origin of the latemotor responses. Latencies were measured from thedisplayed stimulus artefact to the start of the evoked

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Jacques Deschuytere, Noel Rosselle, and Constant de Keyser

action potentials. Post-tetanic potentiation of theindirect motor responses, which was evaluated infive subjects, was obtained by a 200 per secondrepetition rate of the stimulus during 20 to 40 seconds.Such a stimulation was performed more proximallyby means of a second isolation unit. In 15 subjectsrecovery curves were elaborated which necessitatedpaired stimuli of equal strength and identicalduration. The equipment was a MS-3R Medelecapparatus with a fibre optic recorder and a separatelymounted Polaroid camera. Tendon taps and blowsat the styloid process of the radius were applied bymeans of a tapping device that triggered the sweepof the cathode ray oscilloscope. The effects ofvibratory muscle stimuli on the secondary motorresponses were studied in 30 subjects. The vibratorwas an electromagnetic massage apparatus with avibrating plate 2 cm in diameter, beating at afrequency of 100 Hz with an amplitude of 1 to 2 mmand/or a TVR HV- 11 D vibrator (Heiwa ElectronicInd. Co., Ltd., Osaka, Japan). The pathologicalconditions studied will be described together withthe results.

RESULTS

In every normal subject indirect motor responses(IMRs) were recorded from the flexor carpiradialis (FCR) muscle with an electrical stimulus(ES) intensity which was subliminal, liminal,slightly supraliminal, but always inframaximalfor the direct motor responses (DMRs). SimilarIMRs were derived from the palmaris longus(PL) muscle. When the stimulating electrode wasmoved proximally, the IMRs appeared with

briefer latencies, indicating that the late motorresponses were of central origin. In Fig. 1recordings from the FCR muscle are demon-strated when percutaneous stimulation wasperformed using an ES intensity which wassubliminal for the DMR. There are 10 super-imposed recordings in both photographs,illustrating the stability of the IMRs latency.Small differences of the latencies were observedbetween the ipsi- and the contra-lateral side (lessthan 1.0 ms). In different subjects the latenciesranged from 15 to 17 ms and were related to theheight and the age of the person. As seen in thesequence of Fig. 2, an increasing intensity ofthe ES provokes a series of variations of theIMRs and DMRs comparable with what hasbeen described for the soleus muscle. As thestrength of the ES was increased the amplitudeof the second motor response may enhance;when a small DMR wave occurred, the secondarymotor discharges sometimes showed a slightincrement together with an increasing DMR. Afurther enhancement of the stimulus intensityincreased the amplitude of the DMR andconcomitantly the amplitude of the IMR woulddecrease because the motor fibres of the nervetrunk became antidromically blocked. From theforegoing, it was evident that we were able toestablish recruitment curves of the IMRs andDMRs as reported for the soleus muscle. Typicaland representative recruitment curves of theIMR (H wave) and the DMR (M wave) derivedfrom the FCR muscle are shown in Fig. 3. There

FIG. 1 Indirect motor responses derivedfrom the flexor carpi radialis muscleafter percutaneous electrical stimulationof the median nerve in the cubitalfossa.There are 10 superimposed recordingswith an electrical stimulus strength whichis subliminalfor the direct motorresponse. The amplitude marker,indicated in the upper trace, means100 , V in both photographs. Theduration of the electrical stimulus is1.0 ms and is shown in the lower trace.The latency in both photographs remainsremarkably stable (16.5 ms).

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Monosynaptic reflexes in the superficialforearm flexors in man and their clinical significance

FIG. 2 Indirect and direct motorresponses in theflexor carpiradialis muscle duringpercutaneous electricalstimulation with increasingintensity. The sequence ofevents(see text) is comparable with thatdescribedfor the soleus muscle.The arrangement is the same as inFig. 1. The amplitude calibrationis 100 uV in A and B, and1000 ,uV in the followingphotographs.

is a shift to the left of the M wave curve whencompared with the classical recruitment curvesdescribed for the soleus muscle (Hugon, 1973).Variations of the M wave curve in one subjectare demonstrated in Fig. 4 with an invariableIMR (H wave) curve. Slight displacements of thestimulating electrode may provoke these varia-

tions and the shift to the left of the M wavecurve may be more accentuated.The study of the recruitment curves indicated

that the maximal amplitude of the IMR wasreached with an intensity of the ES that evoked aDMR of about the same amplitude. The controlof a quasi-invariable DMR of such an amplitude

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FIG. 3 Typical recruitment curves of the direct andindirect motor responses in the flexor carpi radialismuscle in a normal subject. One point represents themean value of 10 measurements. Ordinate: amplitudein millivolts. Abscissa: intensity of the electricalstimulus in volts.

was used to maintain a stable experimental condi-tion (Fig. 5) when vibration was applied to thetendon. Special attention was paid to ensure

isometric contractions during vibratory stimu-lation. The effects of vibratory stimulation areillustrated in Fig. 6. During vibration of thetendon of the FCR muscle the IMR disappearedalmost immediately and completely in all of thesubjects. The complete abolition of the IMR was

not surprising when de'tecting with a coaxialneedle electrode as earlier experiments with suchan electrode inserted in the medial gastrocnemiusmuscle furnished identical data. When vibrationwas stopped, the H wave reappeared within one

second, and in most instances the H wave

amplitude reached the initial voltage one secondafter the cessation of the vibratory stimulus.Thereafter, a rebound effect was usually observedand the maximum rebound effect was commonly

FIG. 4 Slight displacements of the stimulatingelectrode may give different curves of the direct motorresponse in one subject with an invariable curve of theindirect motor response. The arrangement is the sameas in Fig. 3.

seen after three seconds, then it declined graduallyand subsided four to six seconds after itsmaximum voltage (Fig. 7).

Recovery curves of the IMRs were constructedin 15 subjects. The electrical stimulus strengthwas near-threshold or slightly supraliminal fora direct motor response (Fig. 8). Figure 8demonstrates the initial facilitation phase. Therewas a striking similarity between the typical andrepresentative recovery curve derived from theFCR muscle (Fig. 9) and those recorded fromthe gastrocnemius-soleus muscles. There is noneed to repeat the distinctive phases of theclassical recovery cycles and what they areascribed to (Magladery et al., 1952; Olsen andDiamantopoulos, 1967; McLeod, 1969). The latephase of recovery was found to be a phase ofdepression in all subjects.

Isometric and isotonic contractions of the ipsi-lateral quadriceps muscle without any concomi-tant activation of the forearm flexors substantially

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FIG. 5 Control of a quasi-invariable direct motorresponse in the presence ofan indirect motor response

of abouit the same amplitude (see Fig. 2, E and F).Amplitude marker: 1000 ,u V.

reinforced the IMRs. In 15 subjects an increase of50-1000, of the amplitude was observed with thepreviously mentioned technique of controlledstable DMRs. With an intensity of the ES whichwas threshold for the DMRs a greater enhance-ment of the amplitude of the IMRs was currentlyseen.

Tetanic stimulation of the median nerve,

causing a tonic contraction of the forearmflexors, clearly potentiated the IMRs derivedfrom the FCR muscle, with a maximum effect

FIG. 6 The effects of vibration of the tendon of theflexor carpi radialis muscle on the direct and indirectmotor responses elicited in this muscle. The effects ofpostvibratory potentiation observed for the indirectmotor responses recorded from the same muscle.A: control M- and H-waves. B: vibration applied tothe tendon. C: M- and H-waves after the cessation ofvibration; rebound effect.

five to 10 seconds after the end of the tetanus.The increase of the IMR amplitude may reach50-75 %, if the ES strength was threshold for theDMRs. Post-tetanic potentiation declined after10 seconds and usually subsided completely20 seconds later.

Considering mechanically induced reflex re-sponses, one should remember that the mono-synaptic pathway of the tendon jerk response andthe H reflex in the soleusgastrocnemius muscleshas been well established in normal subjects(Magladery et al., 1951). Although they use identi-cal pathways, the H and tendon jerk reflexesapparently are not true counterparts ofeach other(Herman, 1969). Moreover, in subjects with brisk

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FIG. 7 Time course of the eflects of vibratory stimulation ofthe tendon on the indirectmotor responses recordedfrom the flexor carpi radialis muscle. Abscissa: duration ofvibration is indicated as a heavy black line.

FIG. 8 This series ofphotographsdemonstrates the initialfacilitationphase of the recovery cycle. Pairedstimuli ofequal strength and identicalduration (1.0 ms) were delivered tothe median nerve with an increasing

interval between the conditioning andthe test stimulus (4 ms; 9 ms; 14 ms;19 ms). Amplitude marker: 1000 , V.

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stretch reflexes, a blow to the Achilles tendon mayproduce a contraction of the ipsilateral hamstringmuscles together with the triceps surae. Occasion-ally other muscles may also respond-forexample, the ipsilateral quadriceps muscle andthe contralateral thigh adductors and kneeflexors-and this was termed reflex irradiation or

spread of phasic muscle reflexes (Lance and DeGail, 1965). An analogous reflex irradiation isfound in the upper limb by the direct bone per-cussion of the styloid process of the radius-thatis, the brachioradialis reflex and the accompany-ing contraction of other muscles-apart from thesuperficial forearm flexors, the remote con-tractions of biceps brachii, pectoralis major,triceps brachii, and finger flexors in susceptiblesubjects (Lance and De Gail, 1965; Lance et al.,1973). It seems likely that the stretch stimulus istransmitted mechanically to the receptors ofother muscles through the skeletal structures ofthe limb to adjacent regions as a vibration wave.Independent afferent nerve fibres producing thesecontractions were substantiated by differentialblocking of the peripheral nerves (Lance andDe Gail, 1965; Lance et al., 1973). In addition,Teasdall and Magladery (1974) provided evidencethat after a blow to the styloid process of the

radius, the latencies of the brachioradialis muscleresponse and the forearm flexors responses wereidentical in any one subject. In the same reportthe authors demonstrated in hemiplegics that Hreflexes derived from the brachioradialis muscleand the forearm flexors, after stimulation of theappropriate nerves (radial and ulnar nerve),exhibited similar latencies. These findings, ofcourse, lend support to the basic inference putforward above, that the brachioradialis reflex andthe concomitant contractions of the forearmflexors resulted from independent myotaticreflexes. For comparative purposes we re-investigated, with a blow to the styloid process,the latencies of the brachioradialis muscle reflexand of the accompanying reflex contractions ofthe FCR and PL muscles. If selective tendon tapof these forearm flexors was performed, thelatencies were similar to those obtained after thepercussion of the styloid process of the radius.Finally, the latencies of the IMRs derived fromthe superficial forearm flexors were similar to thelatencies obtained after selective tendon tap andafter the brachioradialis reflex.An account of the patients examined will be

given in broad outline to stress some basicprinciples as they are conceived by the authors.

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Measurements of the latency of IMRs in theFCR and PL muscles offer a diagnostic tool forchronic compression syndromes. This was foundin the chronic compression ofthe C7 nerve roots,middle trunks, and medial cords of the brachialplexus, the affected side being compared withthe contralateral side. In chronic lesions, andeven in more acute lesions, the absence of theIMRs, or a reduced amplitude of these responsescompared with the unaffected side, may indicatea more selective involvement of the Ia afferentfibres when no appreciable motor fibre loss couldbe disclosed. In generalized peripheral neuro-pathies latency measurements of the H reflexesare proposed as a supplementary investigation,particularly in alcoholic polyneuropathies(Blackstock et al., 1972). In idiopathic poly-neuropathy (Guillain-Barre-Strohl) extremelyincreased latencies have been observed in pareticlimbs even at a time when the distal conductionvelocities of motor and sensory fibres were notsubstantially decreased. Thus, measurements ofthe IMR latencies provide a prominent contri-bution to the early diagnosis of idiopathicpolyneuropathy, when the upper limb is initiallyand primarily affected.

Vibration induced inhibition of the IMR wasabsent or reduced in spastic hyperreflexia of theupper limb. This was investigated in 20 hemi-plegics and usually correlated with the degree ofspastic paralysis. It is of interest to recognize anearly involvement of the upper motor neurones,for instance in limited cerebral cortex lesions orconfined damage of the pyramidal tracts whichaffect the upper limb. Further, some neurologicaldisorders involving the pyramidal tracts maypredominantly disturb the upper extremity aswe have found in pseudobulbar palsy, familialamyotrophic lateral sclerosis, and subacutecombined degeneration of the spinal cord, whenno noticeable hyperreflexia was present in thelower limbs.

DISCUSSION

For the characteristics of the H wave and theF wave in normal adults the reader is referred toHoffmann (1918), Magladery and McDougal(1950), Hagbarth (1962), Angel and Hofmann(1963), Mayer and Mawdsley (1965), Hagbarth

and Eklund (1966), and Mayer and Feldman(1967). It has been concluded that the H wave isa monosynaptic response evoked by the electricalstimulation of the larger Ia afferent nerve fibresand that the F wave consisted, partially at least,of recurrent discharges.

In this study secondary motor responses withonly the characteristics of the H wave could bederived from the FCR muscle in 50 normaladults. Bilateral detection was performed in 20subjects and, in addition, these late motorresponses were recorded from the PL muscle inanother 20 subjects. Detecting with needleelectrodes, the IMRs could be elicited withoutany DMR, and when the intensity of the ES wasincreased the fluctuations of both responsesfollowed the course of variation of the H and theM wave derived from the medial gastrocnemiusmuscle (Deschuytere and Rosselle, 1971).

If the stimulating electrode was located moreproximally, the latency of the IMR decreased; itis clear that the spinal origin of the IMR isresponsible for the decrease of the latency. Whenthe stimulating electrode is positioned at the samelevel, the configuration of the IMRs may vary,but the latencies did not change at all if theinitial deflection was controlled, and this wasimportant for measuring latencies in chroniccompression syndromes.When the recruitment curves are considered

one can notice the shift to the left of the DMRcurve in the FCR muscle in comparison with theM curve derived from the soleus muscle (Hugon,1973). This may be explained partially by thedifferences of the respective diameters of theefferent and afferent fibres in the median nerveand in the tibial nerve. Some considerations onfibre size were presented in our previous papers(Deschuytere and Rosselle, 1971, 1973).The complete abolition of the IMRs during

vibration furnished a cogent argument forregarding these late motor responses as mono-synaptic reflexes. Suppression ofsecondary motorresponses has been reported only for mono-synaptic reflex activity (Hagbarth and Eklund,1966; Delwaide, 1973; Hagbarth, 1973; Lanceet al., 1973). Further, it is known from animalexperiments that the F waves are not altered byvibratory stimulation (Lance et al., 1973), so itwould be difficult to interpret the IMRs in theFCR muscle as F waves. Recording with coaxial

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Monosynaptic reflexes in the sluperficialforearm flexors in man and their clinical significance

needle electrodes the IMRs represent only theactivity of a small bundle of muscle fibres.Complete disappearance of the IMR duringvibration was probably due to the fact that a

sufficient number of muscle spindle primaryendings were quite easily activated, resulting in a

prominent presynaptic inhibition of the motorneurones involved. Homonymous and heterony-mous Ia collateral fibres play a role in presynapticinhibition and the effects of antagonist muscleshave to be taken in account (Lance et al., 1973).Intramuscular recording appeared to be more

accurate for studying vibratory effects on theIMRs of the FCR muscle, as was observed forthe H reflex in the medial gastrocnemius muscle.In this connection we have to propose an ESstrength evoking triphasic DMRs and IMRs ofequal amplitude which enabled us to maintain a

stable experimental condition. Thus, with a

DMR of constant voltage the variations of theIMRs reflected the fluctuations of excitability ofthe alpha motor neurones which was experiencedwhen the subject was turning the head or movingthe lower limbs, and real reinforcementmanoeuvres increased the IMR amplitude up to100%.The Jendrassik handgrip has been recognized

as a genuine reflex facilitation. It was a matter ofcontroversy whether there was a real contributionof fusimotor activation (gamma loop) undernormal conditions. Alpha loop activation inreinforcement manoeuvres, producing a higherlevel of excitability of the alpha motor neurones,

was demonstrated by Clare and Landau (1964)using the differential nerve block technique.Percutaneous recording from single human nerve

fibres with tungsten electrodes, developed anddescribed by Hagbarth and Vallbo (1967) andVallbo and Hagbarth (1968), allows directrecording from Ia afferent fibres (Vallbo, 1973).Burg et al., (1974) observed a marked increase ofmuscle spindle afferent activity during a remotecontraction-namely, in the tibial nerve duringthe Jendrassik manoeuvre and in the mediannerve during a contraction of the ipsilateralquadriceps muscle. In this way forearm musclespindle activation and tendon tap reinforcementwere shown for the FCR and PL muscles. Wewere able to demonstrate reflex reinforcement inboth forearm flexors utilizing the IMRs in 15subjects and, detecting with needle electrodes, we

never observed accompanying action potentials.The data of Burg et al. (1974) indicated thatthere is accelerated spindle activity in completelyrelaxed muscles during remote contractions, andthe authors assumed that these findings consti-tuted one piece of evidence for the contributionof the fusimotor system to the reinforcement ofphasic reflexes. On the other hand, Hagbarthet al. (1975) describedEMG signs ofunintentionalcontractions occurring in the receptor-bearingmuscle during reinforcement manoeuvres.Whether the increased spindle activity is associ-ated with a voluntary contraction or not, Hreflexes are likely to be facilitated through thegamma loop and the alpha loop during re-inforcement manoeuvres, and it is known thatH reflexes are indeed enhanced during slightactive contraction of the muscle involved(Hoffmann, 1918).

Post-tetanic potentiation of mechanically andelectrically induced monosynaptic reflexes hasbeen demonstrated by Hagbarth (1962) in normalman. For technical reasons we have investigatedonly five subjects, and found that the IMRs ofthe FCR and PL muscles consistently increasedin amplitude with a maximum effect five to 10seconds after the end ofthe tetanus. From animalexperiments it was concluded that post-tetanicpotentiation was a state oflong-lasting facilitationof presynaptic origin, based on a propertyobviously residing in the afferent nerve terminalsand synaptic knobs (Lloyd, 1949; Eccles andRall, 1951; Granit, 1956; Eccles and Krnjevic,1959). It seems likely that identical mechanismsmay operate at the spinal cord level in man.Since F waves are identified in humans asrecurrent discharges in motor fibres, it isinconceivable that the IMRs derived from thesuperficial forearm flexors, so firmly potentiatedby tetanization, should be regarded as F reflexes.

In view of what has been said previously aboutthe brachioradialis reflex, it is of some interestto remember that the stretch stimulus is trans-mitted mechanically through skeletal structuresas a vibration wave (Lance et al., 1973). Hence,the responses in different adjacent muscles, whichare clearly demonstrated to be monosynapticreflexes (Lance and De Gail, 1965; Teasdall andMagladery, 1974), are probably due to the firstdeflection, with the largest amplitude, of thevibration of the radius after the blow to the

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styloid process. This explanation agrees with thefact that sinusoidal vibration of the tendon mayprovoke a phasic spike in some susceptiblesubjects and more prominently in some spastics,when the vibrator is switched on. Although thetonic vibration reflex develops progressively andappears to be desynchronized with the vibrationcycles, one should take account of a possiblemonosynaptic reflex component together with apolysynaptic one (Hagbarth, 1973; Lance et al.,1973). The findings of Godaux and Desmedt(1975) for the human masseter muscle alsoindicate that the tonic vibration reflex involvesboth a monosynaptic and a polysynaptic reflexpathway.As far as recovery curves are concerned, the

distinctive phases of facilitation and inhibition ofthe conditioned reflex response in the FCR andPL muscles were comparable with those foundin the calf muscles, revealing, apart from beingan argument for the monosynaptic nature of theIMRs, that these superficial forearm flexorsbehave as physiological extensors. Indeed, in allof the 15 subjects, a prominent inhibition wasconsistently seen during the late phase of theexcitability cycle. In animal experiments this lateperiod of the recovery curve was reported to bedue to the influences of group II afferent fibres,being inhibitory for an extensor and excitatoryfor a flexor muscle (Bianconi et al., 1964a, b;Granit et al., 1966), and it was assumed byMcLeod (1969) that the same inhibitory effectsof group II afferent fibres may operate in man.

In conclusion, it can be said that some of ourexperiments constitute circumstantial argumentsfor the monosynaptic nature of the IMR andthat most of our observations support the viewthat these IMRs are to be considered as genuineH reflexes as described for the gastrocnemius-soleus muscles. Moreover, the findings in thepathological conditions studied turned out to bein keeping with such a point of view. The clinicalsignificance of the method has to be stressed andit is to be hoped that its simplicity and theinvaluable information that it affords will leadto the very frequent use of these examinations.

REFERENCES

Angel, R. W., and Hofmann, W. W. (1963). The H reflexin normal, spastic and rigid subjects. Archives ofNeurology (Chic.), 8, 591-596.

Bianconi, R., Granit, R., and Reis, D. J. (1964a). Theeffects of extensor muscle spindles and tendon organson homonymous motoneurones in relation to y-biasand curarization. Acta Physiologica Scandinavica, 61,331-341.

Bianconi, R., Granit, R., and Reis, D. J. (1964b). Theeffects of flexor muscle spindles and tendon organs onhomonymous motoneurones in relation to y-bias andcurarization. Acta Physiologica Scandinavica, 61,348-356.

Blackstock, E., Rushworth, G., and Gath, D. (1972).Electrophysiological studies in alcoholism. Journal ofNeurology, Neurosurgery, and Psychiatry, 35, 326-334.

Burg, D., Szumski, A. J., Struppler, A., and Velho, F.(1974). Assessment of fusimotor contribution to reflexreinforcement in humans. Journal of Neurology,Neurosurgery, and Psychiatry, 37, 1012-1021.

Clare, M. H., and Landau, W. M. (1964). Fusimotorfunction. Part V. Reflex reinforcement under fusimotorblock in normal subjects. Archives ofNeurology (Chic.),10, 123-127.

Delwaide, P. J. (1973). Human monosynaptic reflexes andpresynaptic inhibition. An interpretation of spastichyperreflexia. In New Developments in Electro-myography and Clinical Neurophysiology, vol. 3,pp. 508-522. Edited by J. E. Desmedt. Karger: Basel.

Deschuytere, J., and Rosselle, N. (1971). Identification ofcertain EMG patterns of the spinal cord reflexiveactivity in man. Electrophysiological study ofdischargesfrom spinal origin in the anterolateral muscles of theleg in normal adults. Electromyography (Louvain), 11,331-363.

Deschuytere, J., and Rosselle, N. (1973). Diagnostic useofmonosynaptic reflexes in L5 and S1 root compression.In New Developments in Electromyography and ClinicalNeurophysiology, vol. 3, pp. 360-366. Edited by J. E.Desmedt. Karger: Basel.

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Hagbarth, K. E., and Eklund, G. (1966). Motor effects ofvibratory stimuli in man. In Muscular Afferents andMotor Control. Nobel Symposium I, pp. 177-186.Edited by R. Granit. Almqvist and Wiksell: Stockholm.

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Monosynaptic reflexes flexors manJouirnalofNeuirology, Neluroslurgery, andPsychiatry, 1976, 39, 555-565 Monosynapticreflexes in the superficial forearm flexors in manandtheir clinical