The sensation of passive movement at the metatarso-phalangeal joint of the great toe in man. man

Afferent fibres from muscle receptors in the posterior nerve of the cat's knee joint

The properties of some receptors with afferent fibres in the cat's posterior knee joint nerve have been examined, especially those discharging tonically with the joint in intermediate positions between full flexion and extension. Some of these receptors behave like muscle spindles, and respond to manoeuvres which stretch popliteus muscle. Both in single unit and whole nerve recordings their discharge pauses during a popliteus twitch, and can be strikingly augmented by tetanic stimulation of a number of popliteus fusimotor fibres isolated from ventral root filaments. The action of succinylcholine on these receptors closely resembles its effect on popliteus spindle units with fibres sited normally in the popliteus nerve. Other units with properties suggesting origin from popliteus tendon organs were also observed; their fibres and those of the spindle units conducted at Group I velocity. It is concluded that some afferent fibres from popliteus spindles and possibly tendon organs commonly pursue an aberrant course in the posterior articular nerve of the knee joint.

Quantitation of motion perception in the digits: a psychophysical study in normal human subjects

Threshold perception of motion of the digits was obtained in 14 normal subjects. The metacarpophalangeal joint of the index and the fifth finger of each hand and the metatarsophalangeal joint of the hallux of each foot were passively moved up and down with respect to a horizontal plane defined by the palmar or plantar surface. The motion was sinusoidal at frequencies of 0.5 and 5.0 Hz. A mpdified von Békésy paradigm similar to that used in audiometry was utilized to yield threshold levels of motion sensation. There was little difference in the thresholds obtained for the different joints. The difference between high- and low-frequency stimulation, however, was significant (p less than 0.001): the 0.5 Hz threshold was found to range from 0.8 to 1.0 degree, whereas the 5.0 Hz threshold varied from 0.4 to 0.6 degree. It is thought that motion sense is largely dependent on joint receptor contributions, but muscle and cutaneous receptors may also contribute to this proprioceptive sensation.

Efference and the conscious perception of movement

Evidence was sought implicating efference in the conscious perception of movement by having subjects (n = 10) scale the time course of an active (efference present) and passive (efference absent) thumb movement Efference would presumably lead slightly in time the proprioceptive feedback from a movement and therefore cause active movements to be judged as occurring earlier than passive movements. A probe stimulus (10-msec light flash) was interjected at various temporal locations during an auditorily cued thumb movement made under the two conditions. Subjects estimated the temporal location of the flash relative to the occurrence of the thumb movement. Active movements were estimated to occur on the average 43 msec earlier than passive movements (p<.005), suggesting that efference contributed to the conscious perception of the movement.

Eye tracking of self-moved targets in the absence of vision

Smooth pursuit eye movements have been described as resulting from the tracking of self-moved targets in total darkness. This study investigated the nature of the signal responsible for the release of smooth pursuit in this particular situation. Simultaneous monitoring of eye and hand positions shows that in total darkness smooth pursuit can only be released if the imagined target is either passively or actively moved by the subject's hand. An ischaemic block applied at the level of the biceps allowed us to selectively remove the afferent signal preferentially to the efferent copy in tasks involving eye tracking of an imaginary target actively or passively moved. The results show that an afferent signal was necessary and sufficient to release smooth pursuit, whereas the efferent copy alone could not trigger smooth pursuit. However, the efferent copy could play an important role in the phase relationship (prediction) between eye and finger events and in the activation of the concomitantly active saccadic system. Analysis of the eye movement characteristics, in various non-visually guided, load-affected situations, suggested that the main input to the smooth pursuit system was derived, in a non-graded way, from the position detector activation of the target-moving structure.

Joint sense, muscle sense, and their combination as position sense, measured at the distal interphalangeal joint of the middle finger

1. An anatomical peculiarity allows the hand to be positioned so that the terminal phalanx of the middle finger cannot be moved by voluntary effort. When positioned in this way only joint and cutaneous mechanisms subserve position sense. By altering the position of the hand the muscles are again engaged and able to move the finger. Moving the joint then also excites muscular afferents. 2. The position sense of twelve subjects was assessed with and without engagement of the muscles at the joint. Three tests were used in which either angular displacement, angular velocity or duration of displacement were held constant. 3. When muscular attachment was restored, performance in all tests was greatly enhanced. As engagement of the muscles caused little change in the 'stiffness' of the joint, it is unlikely that the improved performance resulted from increased discharges from the joint receptors. Cutaneous mechanisms are unlikely to mediate this improvement as they are likely to have been unaffected by engagement of muscles. It is concluded that intramuscular receptors are partly responsible for normal position sense. 4. In seven of the twelve subjects the test finger was anaesthetized to isolate the contribution of intramuscular receptors. This muscle sense was variable. In some subjects it provided accurate kinaesthetic information but in others the information was crude. If with the test finger anaesthetized subjects exerted voluntary tension with the muscles that move the joint the muscle sense was improved.

The perception of passive joint-movements by cerebral-palsied children

Luce's choice theory provided the psychophysical basis for investigating the ability of cerebral-palsied children to detect passive movement of the elbow joint. The method included testing "yes" responses when the forearm was moved, and "false-alarm" responses of "yes" when no arm movement had occurred. The children were tested with their eyes closed. The results showed that, in general, the children with spastic cerebral palsy had no deficits, or only very minor ones, in passive movement sensation. In contrast, the athetoid children had considerable deficits. It is suggested that the athetoid child is affected by a continuous barrage of irrelevant proprioceptive information and so finds difficulty in discriminating any particular proprioceptive cue.

Proprioceptive illusions induced by muscle vibration: contribution by muscle spindles to perception?

When vibration of 100 hertz was applied to the tendon of the biceps or the triceps muscle, the subject made a systematic misjudgment of the angle at the elbow. During contraction the error could be as much as 40 degrees. The subject thought that the elbow was in the position that it would have assumed if the vibrated muscle had been stretched.

Quantitative comparison of passive motion and tendon reflex responses in biceps and triceps brachii muscles in hemiplegic or hemiparetic man

The clinical impression that severe hyperreflexia is not consistently associated with severe spasticity in hemiplegia or hemiparesis due to vascular pathology was tested by objective measurement in 11 patients. The intensity of tendon reflex responses of the triceps and biceps brachii muscles was measured as the reflex sensitivity ratio (evoked twitch tension/stimulating hammer force). The degree of spasticity was measured as the threshold rate of elbow flexion or extension above which a myotatic response was elicited, determined by both a sudden increase in passive resistance and a burst of antagonist electromyographical activity.

Rate thresholds were rank ordered for flexion data and for extension data with their corresponding reflex sensitivity ratios. Numerous individual discrepancies stood out. Correlation coefficients between rate thresholds and reflex sensitivities determined at two elbow angles were -0.52 and -0.35 during extension, and -0.47 and 0.03 during flexion.

Differences in rate of stretch, differences in the sensory structures stimulated, and differences in the distortion of the organization of motor control may account for the difference in responses to the two tests.

Characteristics of knee joint receptors in the cat

1. The conduction velocities of 278 posterior articular nerve fibres studied in dorsal root filaments ranged from 10 to 110 m/sec. The conduction velocities were distributed similarly to posterior articular nerve fibre diameters determined histologically.2. Two hundred and nine fibres were slowly adapting. Of these, 140 responded only at both marked flexion and marked extension, forty-seven responded only during flexion and twelve only during extension. Four slowly adapting fibres were activated specifically at intermediate joint positions. Outward twist of the tibia (abducting the foot) enhanced the discharge of most slowly adapting joint fibres.3. Two rapidly adapting receptor types were noted. Pacinian corpuscle-like receptors (fourteen fibres) responded transiently to joint movement in any direction regardless of initial position. Phasic joint receptors (thirty fibres) were rapidly adapting at most joint positions but could give a low rate sustained discharge when strongly stimulated.4. Six slowly adapting posterior articular nerve fibres responded to succinylcholine, suggesting that they originated from muscle spindles. Spindle-like receptors were usually tonically active at intermediate joint positions.5. Eleven slowly conducting myelinated fibres responded only to extreme joint movement, which was probably noxious.