GB1192612A - Improvements in or relating to the Representation of the Information Content of EEG Waves - Google Patents

Abstract

1,192,612. Electro-encephalogram apparatus. J.F. TÍNNIES. May 12, 1967 [May 13, 1966], No.22081/67. Heading G1N. A voltage wave, curve a, obtained from electrodes attached to a patients skull is analysed, curves b and c, to obtain the time intervals of successive cycles and these are then translated by means of a linear ramp-voltage generator, curve d, into voltages the amplitudes of which represent the cycle times. The voltages control the deflection of a recording or display device which is arranged to produce an indication only when in its final deflected portion. A record or display is thus built up as a pattern of dots as shown in curves f and g, where each dot indicates one cycle of the wave, successive dots being displaced in the horizontal direction in accordance with their times of occurrence and in the vertical direction in accordance with the times of the cycles they represent. As illustrated, the cycle times are determined from the times at which the wave makes successive crossings of the zero axis in a given direction. Trigger pulses are produced at these times and are employed to control the rampvoltage generator. As an alternative, the times may be determined from the passage through successive peaks. In general, the cycle time may be determined from consecutive attainment of corresponding values of voltage in a complete cycle. The voltages representing the cycle times are entered into and read out from two stores which are brought into use alternately under control of the trigger pulses. By the use of a servosystem with a feedback loop, the record or display device may be released to make an indication, when in its finally deflected position, by detecting when the current in the servosystem falls to a minimum. Alternatively, the release may be effected by the trigger pulse at the commencement of the next cycle. Reference is made (without giving details) to the use of electric current and heat responsive paper recorders, ink recorders, light beam recorders and cathode-ray tube systems. Reference is also made to arrangements for controlling the size of the reproduced spots in accordance with the amplitude of the waves during the corresponding cycles. Apparatus for carrying out the invention is described, in block diagram form only, with reference to Fig. 1 (not shown).