PubMed · 7804683
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H Kazeem. 1994. Outdated ECT machines.. https://doi.org/10.1192/bjp.165.4.555b
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The use of single fibre electromyography (SFEMG) in the study of neuromuscular transmission across individual motor endplates in situ is reviewed. The neuromuscular jitter can be studied both during voluntary contraction and electrical activation of the muscle fibre. The differences, pitfalls and advantages of these methods are discussed. Findings in myasthenia gravis and other disorders of the neuromuscular transmission are examined.
The activity of single motor units in human muscles can be recorded with relative ease, and the spike train of a single motor unit precisely reflects the spike train of the parent motoneurone. This has led to the proposal of a number of methods to estimate stimulus-evoked post-synaptic potentials in human motoneurones. All of these methods rely on manipulating the spike trains of motor units over a number of trials. All are based on a number of assumptions, all have limitations, and none so far have passed the test of a direct comparison of the estimate of the shape of the post-synaptic potential with a direct intracellular measurement of it. These techniques are summarised in this review.
1. We have studied the effects of changes in posture on the motor response to galvanic vestibular stimulation (GVS). The purpose of the experiments was to investigate whether the function of the GVS-evoked response is to stabilize the body or the head in space. Subjects faced forwards with eyes closed standing with various stance widths and sitting. In all cases the GVS-evoked response consisted of a sway of the body towards the anodal ear. 2. In the first set of experiments the response was measured from changes in (i) electromyographic activity of hip and ankle muscles, (ii) the lateral ground reaction force, and (iii) lateral motion of the body at the level of the neck (C7). For all measurements the response became smaller as the feet were placed further apart. 3. In the second set of experiments we measured the GVS-evoked tilts of the head, torso and pelvis. The basic response consisted of a tilt in space (anodal ear down) of all three segments. The head tilted more than the trunk and the trunk tilted more than the pelvis producing a leaning and bending of the body towards the anodal ear. This change in posture was sustained for the duration of the stimulus. 4. The tilt of all three segments was reduced by increasing the stance width. This was due to a reduction in evoked tilt of the pelvis, the bending of the upper body remaining relatively unchanged. Changing from a standing to a sitting posture produced additional reductions in tilt by reducing the degree of upper body bending. 5. The results indicate that the response is organized to stabilize the body rather than the head in space. We suggest that GVS produces a vestibular input akin to that experienced on an inclined support surface and that the function of the response is to counter any threat to balance by keeping the centre of mass of the body within safe limits.