关键词：
NEUROPHYSIOLOGY/apparatus and instruments
摘要：
When studying processes in which, the interval between successive impulses changes only slowly, at a more or less constant rate, satisfactory results can be obtained by the use of counting-rate meters of conventional design. Such an instrument1, directly indicating the frequency per second of the impulse discharge studied, coupled,to an ink-writer for continuous recording of the frequency variations, has proved to be of great value for the exploration of tha discharge patterns of single units of the central nervous system2. However, a rate meter of this type, based on an integrating network exhibiting a time constant, is not able to follow rapid variations in pulse intervals, and a complementary method has therefore been developed which permits an easy survey of the spacing of the individual nerve impulses. Although the apparatus has certain limitations in comparison with the elaborate pulse-interval meter recently described by Andrew and Roberts3, it has the advantage of being simple, as appears from the block diagram Fig. 1Fig. 1. Block diagram of display unitFig. 2. Recorded impulse pattern from a proprioceptive nerve fibre. The first impulse is that in the top left-hand corner. The sequence is indicated by the arrows below showing the movement of the cathode ray. The yertical separation of successive horizontal sweeps is not constant but depends on variations in the impulse patterns (see text)The oscillograph is provided with facilities for brightness modulation and for single-stroke sweep operation along the X-axis. A slow external, single-stroke, sweep circuit is connected to the F-plates. The intensity control of the oscillograph is set low so as to suppress the spot. The train of nerve impulses to be investigated is passed through an amplitude discriminator producing one square wave pulse of a few hundred microseconds duration for each incoming impulse exceeding a pre-set amplitude. The first pulse in the train triggers both the horizontal and vertical time-
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