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  • 1
    Electronic Resource
    Electronic Resource
    The corticomotoneurone connection is normal in Parkinson's disease (1984)
    [s.l.] : Nature Publishing Group
    Nature 310 (1984), S. 407-409 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Merton and Mortoir demonstrated that brief high-voltage electric shocks to the scalp or spine from a low output resistance stimulator activate visual cortex, motor cortex and spinal cord3"5. Such high-voltage shocks (400 V, giving a peak current of 100-1,000mA) appear to decrease skin resistance6 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/310407a0
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of motor cortex stimulation on spinal interneurones in intact man (1984)
    Springer
    Experimental brain research 54 (1984), S. 382-384 
    Details
    ISSN: 1432-1106
    Keywords: Cortical stimulation ; Ia inhibition ; H-reflex ; Spinal cord ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of a descending corticospinal volley on a spinal inhibitory pathway, has been studied in five intact human subjects. Approximately 63% inhibition of the H-reflex evoked in wrist and finger flexor muscles, was produced by motor threshold stimulation of the radial nerve. When a submotor threshold cortical shock was given 2 to 4 ms before the H-reflex, this inhibition was reduced to approximately 38%. The timing of this effect is compatible with either a monosynaptic or disynaptic corticospinal tract projection onto the spinal inhibitory interneurone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236241
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  • 3
    Electronic Resource
    Electronic Resource
    Eye acceleration during large horizontal saccades in man (1997)
    Springer
    Experimental brain research 113 (1997), S. 153-157 
    Details
    ISSN: 1432-1106
    Keywords: Saccade ; Acceleration ; Eye ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pattern of acceleration was recorded during horizontal saccadic eye movements using a lightweight accelerometer fixed to a scleral contact lens. Horizontal saccades of 15–20° were dominated by either several pulses of acceleration, with a frequency of around 40 Hz, or a single acceleration-deceleration wave followed by lower amplitude polyphasic activity of about 80 Hz. These features are unlikely to be due to slippage or resonance in the contact lens-accelerometer system, as very similar patterns of acceleration were simultaneously recorded with an accelerometer taped over the closed eyelid of the contralateral eye. Analysis of simultaneous surface electromyogram recordings indicated that the multicomponent acceleration profiles were the product, at least in part, of the rhythmic and synchronous modulation of eye muscle discharge during saccades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02454151
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  • 4
    Electronic Resource
    Electronic Resource
    Motor strategies involved in the performance of sequential movements (1986)
    Springer
    Experimental brain research 63 (1986), S. 585-595 
    Details
    ISSN: 1432-1106
    Keywords: Movement ; Sequence ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study analyses the strategies adopted by normal subjects when they are asked to make two separate movements as rapidly as possible one after the other. Five subjects performed the following sequential movements in their own time. 1) Squeeze an isometric force transducer between fingers and thumb to a force of 30 N and then flex the elbow of the same arm through 15°. 2) Squeeze the transducer with one hand and then flex the elbow of the other arm. 3) Perform an isotonic opposition of finger and thumb and then flex the elbow of the same arm. 4) First flex the elbow through 15, 30 or 45° and then squeeze the transducer. 5) Flex and then extend the elbow as rapidly as possible. In tasks 1–4 there was no correlation between the times taken to complete the two separate components of the sequence. Because of this we suggest that the two movements remained under the control of two separate motor programmes. In contrast, in task 5, the times taken for the two components were correlated and hence we suggest that in this case a single programme was used to perform the sequence. In tasks 1–3, in which the mean duration of the first movement was some 135–162 ms, there was a mean pause of about 85 ms before the start of the second movement. Subjects tended to chose a minimum inter-onset latency between the start of the first and the start of the second movement of a sequence of some 230 ms. The reason for this appeared to be that if subjects were encouraged to decrease their interonset latencies to less than 200 ms, the speed of the second movement decreased sharply. However, if the duration of the first movement was prolonged as in task 4, the second movement could be delayed, although there now was little or no pause between the two movements. We conclude that when a single motor programme is run, it is followed by a “relative refractory period”. If a second programme is run within this period, it cannot be executed without loss of speed. Switching from one motor programme to another is achieved with an optimal minimum delay of 200 ms. Sequential movements which are controlled by a single programme do not share this limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237481
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  • 5
    Electronic Resource
    Electronic Resource
    Cerebral potentials and electromyographic responses evoked by stretch of wrist muscles in man (1985)
    Springer
    Experimental brain research 58 (1985), S. 544-551 
    Details
    ISSN: 1432-1106
    Keywords: Somatosensory evoked potential ; Long latency stretch reflex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cerebral evoked potential produced by rapid extension of the wrist was recorded from scalp electrodes in normal subjects while they exerted a small background flexor torque (0.24 Nm) against an electric motor. The initial part of the response consisted of a negative deflection (N1) with an average latency of 24.7 ms. This was followed by a biphasic P1/P2 (32 ms) response and a large later negative wave (N2) (76 ms). Passive wrist extension also evoked reflex EMG responses in the forearm flexor muscles which could be resolved into a short latency (25 ms) and long-latency (52 ms) component. The cerebral responses persisted almost unchanged during complete ischaemic anaesthesia of the hand produced by a pressure cuff around the wrist, and were reduced if the stretch was given during voluntary wrist flexion. The primary component (N1-P1/ P2) of the cerebral response probably represents the arrival at the cortex of the muscle afferent volley. However, the significance of the secondary component (P1/P2-N2) is unknown. Under certain conditions, its size was related to the size of the long latency stretch reflex evoked by stretch of the flexor muscles. Thus, increasing the velocity of stretch or decreasing the repetition rate (from 1.0 to 0.15 Hz) at which stretches were applied, increased the size of both the muscle reflex and the cerebral response. The secondary component also could be changed by voluntary reaction to wrist stretch. Changes in the size of the secondary component of the evoked response may represent the earliest cortical sign of interaction between sensory input and motor output.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235870
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  • 6
    Electronic Resource
    Electronic Resource
    Habituation and conditioning of the human long latency stretch reflex (1986)
    Springer
    Experimental brain research 63 (1986), S. 197-204 
    Details
    ISSN: 1432-1106
    Keywords: Stretch reflex ; Habituation ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of stretch repetition rate, prior warning stimuli and self administered stretch were examined on the size of the short and long latency components of the stretch reflex electromyographic EMG response in flexor pollicis longus and the flexor muscles of the wrist and fingers. Stretches of constant velocity and extent were given every 10 s, 5 s, 2 s, or 1 s to either the wrist or thumb during a small background contraction of the flexor muscles. The size of the long latency component of the stretch reflex (measured as the area under the averaged rectified EMG responses) declined dramatically at faster repetition rates, especially in the wrist and finger flexors. The size of the short latency component was relatively unaffected. The size of the electrically elicited H-reflex in forearm muscles also failed to habituate under the same conditions. If each individual trial of a series was examined, the long latency component of the stretch reflex EMG could be seen to decrease in size over the first three to six stretches if stretches were given every 1 s, but not if stretches were given every 10 s. When stretches were given every 5 s to either wrist or thumb, an electrical stimulus applied to the digital nerves of the opposite hand 1 s before stretch reduced the size of the long latency component of the reflex EMG response. The short latency component was unaffected. Self triggering of wrist or thumb stretch by the subject pressing the stimulator button himself with his opposite hand, also decreased the size of the long latency component of the reflex EMG response without affecting the short latency component. It is concluded that factors other than stretch size or velocity can have marked effects on the size of the long latency component of the stretch reflex. These factors must be taken into account when comparing values of reflex size obtained with different stretching techniques and in different disease states in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235664
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  • 7
    Electronic Resource
    Electronic Resource
    Postural electromyographic responses in the arm and leg following galvanic vestibular stimulation in man (1993)
    Springer
    Experimental brain research 94 (1993), S. 143-151 
    Details
    ISSN: 1432-1106
    Keywords: Vestibular system ; Galvanic stimulation ; Posture ; Electromyogram ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Application of a small (around 1 mA), constant electric current between the mastoid processes (galvanic stimulation) of a standing subject produces enhanced body sway in the approximate direction of the ear behind which the anode is placed. We examined the electromyographic (EMG) responses evoked by such stimulation in the soleus and in the triceps brachii muscles. For soleus, subjects stood erect, with their eyes closed, leaning slightly forward. The head was turned approximately 90° to the right or left relative to the feet. In averaged records (n=40), current pulses of 25 ms or longer modulated the EMG in a biphasic manner: a small early component (latency 62±2.4 ms, mean ± SEM) was followed by a larger late component (latency 115±5.2ms) of opposite sign, which was appropriate to produce the observed body sway. The early component produced no measurable body movement. Lengthening the duration of the stimulus pulse from 25 to 400 ms prolonged the late component of the response but had little effect on the early component. Short- and long-latency EMG responses were also evoked in the triceps brachii muscle if subjects stood on a transversely pivoted platform and had to use the muscle to maintain their balance in the anteroposterior plane by holding a fixed handle placed by the side of their hip. The latency of the early component was 41±2.6 ms; the latency of the late component was 138±4.3 ms and was again of appropriate sign for producing the observed body sway. Galvanic stimulation evoked no comparable responses in either triceps brachii or soleus muscles if these muscles were not being used posturally. The responses were most prominent if vestibular input provided the dominant source of information about postural stability, and were much smaller if subjects lightly touched a fixed support or opened their eyes. The difference in latency between the onset of the early component of the response in arm and leg muscles suggests that this part of the response uses a descending pathway which conducts impulses down the spinal cord with a velocity comparable with that of the fast conducting component of the corticospinal tract. The late component of the EMG response occurs earlier in the leg than the arm. We suggest that it forms part of a patterned, functional response which is computed independently of the early component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230477
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  • 8
    Electronic Resource
    Electronic Resource
    Control of frontal plane body motion in human stepping (1997)
    Springer
    Experimental brain research 115 (1997), S. 345-356 
    Details
    ISSN: 1432-1106
    Keywords: Key words Balance ; Walking ; Movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  During a step the body’s centre of mass (CoM) typically remains medial to the supporting foot and therefore the body is unstable and falling (sideways) under gravity. This may make it difficult to adjust the frontal-plane body motion appreciably once the step is under way. We have therefore investigated whether this motion could be controlled largely in a ballistic manner, that is by setting the initial (toe-off) position and velocity of the CoM such that the fall develops as required for the particular step without the need for appreciable mid-step adjustment. Subjects stepped in different directions and from different postures, and the resulting motion of their CoM in the frontal plane was compared with that of a single-segment mathematical model of the body which falls freely under the influence of gravity. The lateral position and velocity of subjects’ CoM at toe-off varied across the different step types in a manner consistent with a ballistic mode of control. Furthermore the model, given these positions and velocities as initial conditions, closely predicted the subsequent CoM motion. The results suggest that subjects may produce the different body trajectories required for different types of step largely in a ballistic manner. This would imply that the central nervous system must judge in advance the size and direction of the initial ”throw” given to the body-mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005703
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  • 9
    Electronic Resource
    Electronic Resource
    Primary orthostatic tremor: further observations in six cases (1992)
    Springer
    Journal of neurology 239 (1992), S. 209-217 
    Details
    ISSN: 1432-1459
    Keywords: Orthostatic tremor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The clinical and physiological features of six new patients with primary orthostatic tremor are described. We suggest that use of the term primary orthostatic tremor be confined to the clinical syndrome in which unsteadiness when standing is the predominant complaint and accompanied by characteristic electrophysiological findings of a rapid (frequency around 16 Hz), regular leg tremor which is not influenced by peripheral feedback, is synchronous between homologous leg muscles, and in certain postures of the upper limbs, between muscles of the arm and leg. The fast frequency of muscle activity in primary orthostatic tremor of the legs causes unsteadiness when standing (presumably due to partially fused muscle contraction) but only a fine ripple of muscle activity is visible. In contrast, the slower frequency of other leg tremors, for example essential tremor, results in obvious leg movement which is evident in many leg postures, is variable over time and can be reset by a peripheral nerve stimulus. Essential tremor and orthostatic tremor do not respond to the same therapies, suggesting differences in the pharmacological profiles of the two conditions. Accordingly, there are clinical, physiological and pharmacological differences between primary orthostatic and essential tremor. Whether these factors are sufficient to regard these tremors as separate conditions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00839142
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