OBSERVATIONS ON THE CORTICAL EVOKED POTENTIALS OF THE RABBITS TO AUDITORY STIMULI USING AVERAGING TECHNIQUE
Kiichiro Taguchi · Nippon Jibiinkoka Gakkai Kaiho · 1967
The cortical evoked potentials of the waking rabbits to auditory stimuli were observed with Average Response Computer analog type.The chronically indwelled active electrodes were placed upon extradurally in four bisymmetric points of the frontal, parietal, occipital and temporal areas.The auditory stimuli were tone pips with peak frequencies of 300, 600, 1200, 2400, 4800 and 6800cps.The following results were obtained.1. Basic types of the cortical evoked potentials of waking rabbits to auditory stimuli consisted of 3 phases of waves; positive (P1), negative (N1) and positive (P2).2. This potential was largest at or near the vertex and smallest at the occipital area.There was no difference between the evoked potentials of corresponding areas on the bilateral hemispheres.3. The minimum reaction intensities of the tone pips (thresholds) ranged from 30 to 60dB SPL.Their projections to the frequency-intensity plane are compared with the equal-loudness contours of Fletcher and Munson.4. The peak-latencies of the components of these potentials at the vertex were 25.1 to 32.6 msec (P1), 51.1 to 65.0 msec (N1) and 81.4 to 97.4 msec (P2).The peak-latencies of the evoked potentials to the tone pips of low frequencies (300cps and 600cps) were longer than those to tone pips of higher frequencies.As the intensity of the tone pips is decreased the peaklatencies of N1 and P2 increase.5. The amplitude of the component P1 or P2 versus the intensity of tone pips showed a relationship which corresponded to Weber-Fechner's law, while the com-ponent N1 or P1N1 had a relationship which was compared with Stevens's power law.P1N1 was designated the "Amplitude of the evoked potential".6.The absolute refractory period of the evoked potential was within the limits of 0.1 to 0.3 sec, while the relative refracitory period was about 2.0 sec.7. The amplitude of this evoked potential was var iable day by day.8. Tubocurarine chloride suppressed the component P1 and chlorpromazine augumented P1N1 and increased the peak-latency of P2. 9.By simultaneous recording the amplitude of the extradural potential was slightly smaller than that of the subdural potential and the amplitude of the evoked potential recorded on the skull showed about 20 per cents as much as the subdural potential.10.Habituation of the evoked potential was observed, when those more than 10 or so following auditory stimuli at intervals of 6 sec were given.11.Conditioning due to same interstimulus intervals was most remarkable, when the interstimulus interval was 3sec.12. Alertness of the rabbit gave the evoked potentials variety.Attentien to the stimuli appeared to augument the evoked potential and alertness to the environment seemed to suppress the potential.13.The features of this potential has a strong resemblance to the human V-potential and the origin of the potential seems to be the same as that of the animal secondary discharge during sleep.