Showing papers on "Artifact (error) published in 1975"

Automated analysis of the electrical activity of the human brain (EEG): A progress report

Abstract: Clinical evaluation of electroencephalographic (EEG) recordings is based on complex subjective processes of data reduction and feature extraction. The high dimensionality of the EEG signal, its variability, and the lack of standard population values have retarded development of automated systems. An interactive, real-time analysis system (ADIEEG) has been implemented to develop features to simplify visual interpretation and facilitate automated classification. It uses a 40 000 word PDP15-PDP11 dual processor computer. Resident code occupies approximately 11 000 locations, while a maximum of 12 000 locations are used for buffers. The system performs 1) continuous spectral analysis using the fast Fourier transform to produce estimates of power and coherence, 2) parallel time domain analysis to detect sharp transients significant to diagnosis, 3) several forms of graphics, 4) simple algorithms to reject noncortical and instrumental artifact, 5) interactive parameter alteration and on-line feedback to adjust decision thresholds when necessary, and 6) extraction of diagnostically helpful features using heuristics based on clinical EEG. The ADIEEG system resides in the University of California, San Francisco Medical Center, and Langley Porter Neuropsychiatric Institute.

Flow rate computer adjunct for use with an impedance plethysmograph and method

Abstract: A computer adjunct is described which is used in combination with an impedance plethysmograph. The impedance plethysmograph provides signals related to conductance in a biological segment and related to deviation from a quiescent resistance level in the biological segment as body fluids are pumped therethrough in a pulsatile manner by the pumping action of the heart. The deviation of the segment resistance contains artifact signals such as those imposed by movement or breathing. The computer adjunct contains means for providing a signal indicative of heart pumping rate and circuit means for measuring the level of the artifact signals once each heart pumping cycle and generating a correction signal related thereto. The correction signal is thereafter applied to the deviation signal for reducing error induced by the artifact signals. The heart rate signal is conditioned to obtain a signal related thereto which is averaged. The corrected deviation signal is also averaged. The averaging is performed by circuitry which integrates the corrected deviation signal, thereby reducing residual cyclic noise due to the artifact signal while still affording relatively short output stabilization time. The two averaged signals are multiplied together and then combined with the segment conductance signal for providing an output signal indicating blood flow rate through the biological segment. The combination is capable of blood flow rate measurements for calf segments or thoracic segments.

Errors and artifacts encountered in the monitoring of fetal respiratory movements using ultrasound

Abstract: A study is described of the possible sources of error and artifact arising in the monitoring of fetal respiratory movements using ultrasound, and their effect upon the clinical usefulness of the technique. Major artifacts arose from attempts to use the instrument controls to compensate for a poor choice of insonation direction, and from the use of a belt-mounted transducer. Critical requirements of the necessary instrumentation are discussed, together with the limitations of commercially-available equipment.

The Scandinavian suicide phenomenon: fact or artifact? Another look.

Abstract: The well known differences in suicide rates among the European countries (especially the Scandinavian) are often explained as artifacts of statistical gathering and reporting. It is pointed out that the relative-rate differences reported by these countries obtain to a surprising (and reliable) extent in their immigrants to the United States where such statistics are gathered and reported by the same agents. It is suggested, therefore, that at least some portion of these differences is genuine.

Reversal of partial reinforcement effects in acquisition goal speed: an artifact that continues to stimulate theory

Abstract: The partial reinforcement acquisition effect (PRAE), faster running by panially reinforced than continuously reinforced animals, is often absent or reversed in goal speed measures ( 5 ) . Robbins and Weinstock ( a ) , however, pointed our that the effect can be found in goal speed when subjects cannot detect presence or absence of reward prior to completion of the goal measure. Discussion of the lack of such an effect in goal measures as an intrinsic aspect of partial reinforcement theory prior to 1967 (1, 9 ) , while compatible with the data that were then available, may have been mistaken. Continued treatment of the reversed effect in goal measures as a basic fact ( 4 , 6 , 10 ) gives misplaced attention to a methodological artifact. A growing number of studies have demonstrated the effect in goal measures ( 2 , 3, 7 , 1 1 ) . Unpublished data from cwo experiments in progress at Tulane also show a goal measure effect. Theories dealing with the partial reinforcement effect in acquisition should, at the least, be prepared to provide a basis for predicting when the effect will be found in a goal measure and when it will not.

EEG Artifact Due to a Metallic Prosthetic Eye

Abstract: (1975). EEG Artifact Due to a Metallic Prosthetic Eye. American Journal of EEG Technology: Vol. 15, No. 2, pp. 75-78.