An instrument for automatic scoring of EEG phase relationships

ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY

614

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AN INSTRUMENT FOR AUTOMATIC SCORING OF EEG P H A S E R E L A T I O N S H I P S 1 CHESTER W

DARROW, P H D

AND HAROLD F SMITH

Institute for Juvenile Research, Chicago, Ill (U S A ) (Accepted for pubheatlon August 23, 1963)

The I JR Indicator of EEG Phase Relations (Darrow et al 1956) required manual scoring of the phase compar~son record for easy observatmn and tabulation of results The device here described automat]eally scores leading

respectively to grids 1 and 2 of a push-pull D C amphfier The result is a "hipolar" record in which (a) waves from two compared areas which are equal and m-phase cancel, (b) waves which are m-phase and unequal produce disX3 2NI305

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Fig l Scorer-amphfier and relays See text and laggmgtemporalrelatmnshlps between waves m compared channels and permits automatm tabulation of results In the previously described phase indicator the posmve (or negative) halves of the EEGs from two areas are fed i Reported before the Central Association of Electroencephalographers, Rochester, M m n , October 19, 1962 This study was supported by the Illinois Department of Mental Health

placement m the direction of the larger, and (c) waves m one channel which lead those m the other, result m an unbroken transition of the base line - - priority indicated by the direction of the slope of crossing In practice these phase comparison records have been scored by marking anterior and posterior leading m different colors to facilitate reading and tabulation of results It was desirable, if possible, to ehmlnate the necessity for manual scoring of the phase Indicator record The simplest arrangement, st seemed, would be one m wluch

Electroenceph chn Neurophystol , 1964, 16 614-616

INSTRUMENT FOR AUTOMATIC SCORING

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Fig 2 Phase indicator and phase scorer recording of at 2 5 and 5 0 A/sec of temporal relation between two generator-produced frequencies Accents on indicator record mark unbroken transitions of base line Upward pips on scorer show precedence of lead I, downward pips show precedence of lead II

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the scoring pen would deflect in one direction when one channel leads and In the other direction when the other channel leads Such a method would lend itself also to automatic counting and tabulation of results To be effective the rapid succession of peak voltages in compared channels which, m a push-pull amphfier, results m a rapid reversal of output voltage and m unbroken transition of the phase-indicator base line should, in the phase scorer, produce a positive deflection when a wave m one channel is preceding and a negative voltage when the other channel is preceding Several tube-operated systems were tried out A simple transistor and polarized relay system has provided the most successful solution of the problem The ctrcmt which was finally evolved (by H S ) consists of a transmtor amplifier drwmg a Barber-Coleman mtcroposmoner relay with the contacts of the relay connected to a selectwe gating and timing transistor ctrcmt

driving a penwrlter Examination of the schematm diagram in Fig 1 shows how detection of phase changes is accomplished In the resting state contacts A and B are open and a posltwe charge builds up on condensers Cz and C2 connected respectively to bases of gating transistors X4 and X3 and, due to the characteristics of the orcmt, blocks conduction Near zero collect-to-emitter voltage hkewJse prevents gating Closing of contact A, when phase indicator voltage responds to a prior wave in one of the compared EEG channels, shortclrcults condenser Cz and apphes a positive voltage to the emitter of transistor Xa, but no gating occurs m the absence of negative voltage to the base of Xa If, however, the first EEG wave is immediately followed by a wave in the other compared channel, reversing phase indicator voltage and opening contact A, this permits rechargang of condenser Cz via resistor R1 with Electroenceph chn Neurophystol , 1964, 16 614-616

616

C W DARROW AND H F SMITH

a resulting negative pulse to the base of transistor X4 If during this negatwe pulse there is closing of contact B, a positive voltage is apphed to the emitter of X4 with resulting current flow, and a deflection of the penwrlter (I) Slmdar but opposite effects will occur when EEG waves occur in opposite sequence and contact A succeeds contact B Opening of contact B w)th recharging of condenser Cz will result in a negative pulse to the base of transistor X3 preparing it for conduct)on If, during this negative pulse, contact A is then closed, a pomtive charge on the emitter of X3 will result In gating of X3 and an appropriate pip on the penwrlter (2) Results of the operation of ttus scoring system m parallel with a record of the phase indicator are shown during the beating of two generator-produced frequencies in Fig 2 In Fig 3 is an excerpt showing the apphca-

tton of the method during EEG recording Seven phase scorers are currently in use recording the inter-area time relationships between EEGs from six electrode placemeats SUMMARY A transistor-operated instrument providing continuous automatic scoring of inter-area EEG phase relations is described REFERENCE DARROW, C W , WILCOTT, R C , SIEGEL,A B , STROUP, M and AARONS, L Instrumental evaluation of EEG phase relationships Electroenceph chn Neurophyslol, 1956, 8 333-336

Reference DARROW, C W and SMITH, H F An instrument for automatic scoring of EEG phase relationships Electroenceph chn Neurophystol , 1964, 16 614-616

A TIME LOCKED, LOW LEVEL CALIBRATOR 1 JOHN W EMDE

Division of Medical Electromcs, College of Medlcme, State Umverstty of Iowa, Iowa City, Iowa (U S A ) (Accepted for publication July 17, 1963) When recording electrophysiologlcal data, it is often convenient to have a cahbratIon signal superimposed on the record to provide a known voltage reference If an averaging technique is in use, this calibration pulse must 1 Supported in part by USPHS grant number MY2635

be time locked to the stimulus necessitating some form of electronic waveform generation The calibrator described was designed primarily for use when averaging evoked responses in conjunction with the CAT model 400A, however, the author feels it may have application in other related areas as well Electrodes

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Electroenceph chn NeurophysIol, 1964, 16 616-618