In order to analyze informations in a train of nerve impulses evoked by the external stimuli on the sensory receptor, an electrical device for counting impulse trains was designed. The device consists of the following three major parts.
1) An electronic counter consisting of a counting unit and a D-A converter. Frequency characteristics of the counter is linear from 0 to 4096 pulses/sec and input-output characteristics of the D-A converter is perfectly linear over the full range. When nerve impulses are passed through a slicer which eliminates noise and unwanted signals, the output signal from the slicer triggers a one-shot multivibrator which subsequently generates rectangular pulses. The rectangular pulses are then fed to the counter, which displays frequencies of nerve impulses on a pen-writing recorder.
2) A time interval-display unit consisting of a sawtooth wave form generator triggered by rectangular pulses into which nerve impulses have been converted. After receiving a nerve impulse, a linear time base generator is reset and restarted. The generator produces sawtooth wave forms, V (t₁) = A (t₂-t₁), V (t₂) =A (t₃-t₂), …… for a train of nerve impulses arriving at times t₁, t₂, t₃, ……. Intervals of successive nerve impulses can be shown as the final value of each sawtooth wave form and recorded on a pen-writing recorder.
3) An integrating unit which is used to indicate the response magnitude of compound action potentials in the whole nerve. The response magnitude is presented by the successive integrated value of compound action potentials per unit time, which can be varied from 50 msec to 20 sec.
The device is completely transistorized, compact and portable, and it is considered to be satisfactory for use as a nerve impulse counting device for analyzing data obtained by physiological experiments or as a monitor on line during the course of an experiment.

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Computer diagnosis of the roentgenogram is regarded as a typical two-dimensional pattern recognition problem. As the first step to approach the problem, we investigated the characteristics of the density distribution of the chest roentgenograms by comparing two samples, one is of normal lung and the other of spontaneous pneumothorax. The main results are summarized as follows : (1) The average density varies widely even in a roentgenogram depending on the shape of the lung. (2) Remarkable random components are observed, which are caused by irregular lung markings, photographic granularity and electrical noise of recording device. (3) Highly deterministic patterns (e. g., ribs and vessels) which are not the eventual recognition objects exist. (4) There exist overlaps of various kinds of images including the above three. The density at any point on the film is approximately equal to the superposition of density of each component image.
For realization of automatic processing of such a complex pattern as the roentgenogram, it should be stressed that each of the basic operations suits processing of each corresponding component mentioned above, and their successful consolidation is indispensable.
As one of such basic operations, we studied a detecting method of edge lines of ribs using a simple model hypothesized on the basis of the above results. In the model, the patterns (sets of discrete sample points) consist of regions of two different uniform densities with additive Gaussian noise. The procedure is decided into three steps : (I) The state of each sample point “on edge line” or “not” is estimated by the likelihood ratio estimated from the state of its neighborhood. (II) Two sample points decided as “on edge line” are connected if they are adjacent, thus giving connected graphs. (III) In each connected graph a line being most likely “on edge line” is determined as the recognition result.
Finally results of recognition experiment using a cutout of the middle lobe region including two ribs and tuberculosis region are shown, indicating effectivenss of the method proposed here.

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It is indispensable in the design of pacemaker electrodes to get clear understandings about such properties of stimulating electrodes such as electrode impedance and stimulation threshold. On the basis of the experiments with dog's heart, a simple model of heart muscle and stimulating electrodes was derived, on which a theoretical analysis was made for the electrode impedance, the voltage, current and power thresholds. Experimental results obtained in dogs agree well with the theoretical results. It is concluded that a cathode has an optimum dimension and a larger anode is desirable from the viewpoint of the power threshold. The theory is regarded as a general analysis of the stimulation of living bodies, and the results is applicable to the design of various sorts of electrical stimu lators for biological use.

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This paper is to describe a new type of electrode with spiral needle and its examination. This newly modeled electrode (invented by K. Kitahama) is composed of a spiral needle, a resinous holder and a leading wire.
The needle is made of either white gold or stainless steel and is coiled 3 to 4 turns, with the diameter of 2 mm. The needle is coated with thin layer of insulating material except its end part of 1.5 mm length.
In order to apply the electrode to the head skin, hold it between the thumb and index fingers, attach the point vertically to the head-surface, and turn it 180° by degree. Thus, it will be securely applied onto the surface.
The advantages of the spiral needle electrode are as follows : (1) It is hardly dropped off by violent movement of the subject. (2) As it does not look like a needle, the subject becomes hardly tense or frightened. (3) It is easy to attach. (4) It does not make the subject uncomfortable even when applied for a long period of time. (5) The resistance value (D. C.) between electrodes is 20 to 30 kΩ. (6) Artifacts caused by the contact of the perspiring scalp and the electrodes are rarely found.
Thus, we found that the use of the spiral needl electrode is particularly advantageous in such cases as nervous subjects, restless children, hairy women, subjects with disturbed consciousness, patients for brain surgery, application of various activation methods, multiple factor EEG, group administration of EEG--so called Mass EEG (Wada), and recordings in the busy EEG testing room.

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A biological experiment system using a digital computer has been developed at the Electrotechnical Laboratory in Japan in order to pursue electroencephalography and neurophysiology research projects.
This system gives experimenter the facility for gathering data on the spot and having the computer generate stimulus pattern, process response data of the clinical subjects, and the system sends him analyzed [results in graphical form for deciding what experiment should be made in the next step.
Some of the features of the system are as follows : In the EEG experiments, photic stimuli are given at random to human subjects for suppressing uncorrelated periodic components and reducing adaptation trends. Responses to light flashes are extracted by the average response program.
In the research of the mechanism of vestibulo-ocular system, responses of neurons in the vestibular or abducens nucleus to head rotation are measured by taking post-stimulus histogram and time-interval histogram of neuron discharges.
Correlation calculation and spectrum analysis are performed by off-line operations.

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An automatic temperature control system was devised for a small volume (-6 cm³) preparation chamber to be used in microelectrode techniques. The principle of the device was a negative feedback control system.
The temperature of the preparation was measured by a bead thermistor with a small tip which was placed closely to the preparation. The temperature was converted to voltage by a wheatstone bridge, one of the arms of which consisted of the thermistor.
In order to cool or warm the preparation, two Peltier plates were used. The plate has the following properties : (1) when DC current is passed through the plate in one direction, its upper surface becomes cool and its lower surface warm. When the direction of current is reversed, the temperature of the surfaces is also inverted. (2) The power of cooling or warming increases according to the increase in DC current. Heat generated on the lower surface of the Peltier plates was deprived by perfusing tap water under the Peltier plates. The temperature of the preparation without passing DC current but with water perfusion is referred to as the environmental temperature.
(I) Keeping the preparation temperature below the environmental temperature.
The subtraction of the output of the thermometer from a reference DC voltage, actual signal, was amplified by a chopper DC amplifier (66 dB). Its output drove a relay switch which operated on a power supply for the cooling (warming) device. When the sign of the actual signal was positive, then the cooling device functioned to cool the preparation. When the sign was negative, the cooling automatically stopped, and thus the temperature was kept at a constant level.
(II) Keeping the preparation temperature above the environmental temperature.
The principle was almost the same as stated in (I). The difference was as follows : (1) First, we reversed the polarity of DC current through the Peltier plates. (2) Second, we reversed the sign of the actual signal of (I), so that a positive signal now produced warming of the upper surface of the plate.
With the aid of this device, the preparation temperature was kept constant at a desired temperature between 5°C and 37°C within an error range of ±0.1°C to ±0.25°C. Alteration of the temperature level was easily accomplished by setting the desired reference voltage. The newly set temperature level was reached within a few minutes.

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