PubMed · 7318095
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C Malbrel, M Alame. [Visual function in aniridia].. https://pubmed.ncbi.nlm.nih.gov/7318095/
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Transient voltage responses (charging transients) to current stimulation are presented for a non-linearly tapering cable model of a neurone with a shunt at the soma. Exact expressions are given for the time constants of exponential decay expressed in terms of the passive membrane time constant and the taper rate constant. The effect of a somatic shunt on the membrane potential transients at the soma is shown to result in a more rapid final decay of the membrane potential than simple passive decay with membrane time constant. The theoretical analysis should be of use to electrophysiologists wishing to interpret their experimentally observed charging transients recorded at the some in terms of cable properties of neurones in vivo.
Oscillatory attractor neural networks can perform temporal segmentation, i.e., separate the joint inputs they receive, through the formation of staggered oscillations. This property, which may be basic to many perceptual functions, is investigated here in the context of a symmetric dynamic system. The fully segmented mode is one type of limit cycle that this system can develop. It can be sustained for only a limited number n of oscillators. This limitation to a small number of segments is a basic phenomenon in such systems. Within our model we can explain it in terms of the limited range of narrow subharmonic solutions of the single nonlinear oscillator. Moreover, this point of view allows us to understand the dominance of three leading amplitudes in solutions of partial segmentation, which are obtained for high n. The latter are also abundant when we replace the common input with a graded one, allowing for different inputs to different oscillators. Switching to an input with fluctuating components, we obtain segmentation dominance for small systems and quite irregular waveforms for large systems.
A patient with neuromyotonia, peripheral neuropathy and myasthenia gravis (MG) is described. Neurophysiological studies, at rest, showed continuous muscle discharges of motor unit action potentials (MUAPs) in duplets and triplets. Motor (MNCV) and sensory (SNCV) nerve conduction studies revealed mild axonal and demyelinating peripheral neuropathy. Plasma exchange was followed by disappearance of clinical and electrophysiological signs of neuromyotonia and MG, as well as peripheral neuropathy.