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Planar curve analysis of three-channel auditory brain stem response: a preliminary report
Brain Research, 223 (1981) 181-184
181
Elsevier/North-Holland Biomedical Press
Planar curve analysis of three-channel auditory brain stem response: a preliminary report
J O H N S. WILLISTON, D O N L. JEWETT* and WILLIAM H. M A R T I N
Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA 94143 (U.S.A.) (Accepted July 2nd, 1981)
Key words: auditory brain stem response - - far-field - - three-dimensional - - neural generators - vectorcardiography - - planar curve - - evoked potentials - - mapping
Recordings of auditory brain stem responses (ABRs) were made in guinea pigs by means of farfield computer averaging from three orthogonal electrode pairs. The 'Y' locations were mouth and nuchal ridge, 'X' locations left and right mastoids, and 'Z' locations vertex and throat. Three-dimensional models were constructed to plot simultaneous points from the three averages in a voltage-voltage-voltage space. In all five animals tested, at least three subsets of sequential data points lie in separate planes. The data points in each plane roughly correspond to waves I to III in the guinea pig ABR as recorded from the vertex-throat electrode pair. The planarity of data points is a new observation and is not predicted from the singie-channel recordings. Three-dimensional planes are also found by means of vectorcardiography, which suggests some underlying principle, such as synchrony and homogeneity of anatomical position of the generators. Planar analysis of ABRs may be useful in analyzing and utilizing the additional information obtainable from 'non-standard' electrode pairs.
ABRs (Auditory Brainstem Responses) are far-field potentials that result from progressive activation of the auditory pathway in response to an abrupt auditory stimulus. ABRs are usually recorded between electrodes at the vertex and mastoid ipsilateral to the stimulus. A single averaged response plots voltage versus time and consists in humans of from five to seven waves within the first 10 ms after the stimulus ~,a. Various animal studies have supported the following generalizations: (1) sequential activation of different neural generators is represented in the ABR by a sequence of waves 1,5,7; (2) the potential at any given point in time after the stimulus is an algebraic summation of the potentials of all simultaneously active generatorsS; (3) small differences in electrode location do not significantly change the waveforms in such far-field recording6; and (4) large changes in electrode position can differentially accentuate or diminish different waves with or without phase differences10. The latter observation suggests that different far-field electrode pairs may yield different information concerning the neural generation of the ABR. * To whom correspondence should be addressed at: Special Studies Unit, Department of Orthopaedic Surgery, U-471, University of California, San Francisco, CA 94143 (U.S.A.). 0006-8993/81/0000-0000/$02.50 © Elsevier/North-Holland Biomedical Press
182 We have plotted the data points from three orthogonal pairs of electrodes in a three-dimensional plot and have observed a singular and striking result: certain segments of this plot are planar in configuration. The planarity of three-dimensional ABR data points is not predicted by single-channel ABR averages and may help to distinguish different neural generators that are simultaneously active. Five guinea pigs with normal ears as determined by examination and response to single-channel ABR were used as subjects and were lightly anesthetized with 2 %, halothane in oxygen administered via a face mask. Auditory 'clicks' of 200/~s duration and 60 dB SPL intensity from a T D H 39 earphone were presented monaurally to the right ear at 10 clicks/s through a plastic ear coupling tube that produced a 1 ms conduction delay. Hook-shaped electrodes fashioned from 26-gauge stainless steel hypodermic needles were attached to the scalp in three orthogonal pairs: the ' Y ' pair locations were mouth and nuchal ridge, ' X ' locations left and right mastoids, and 'Z' locations vertex and throat. The ground reference hook electrode was inserted in the skin of the back. Each input signal was amplified by a factor of 105 by a Data Inc. Model 2124 preamplifier with a 1-10 kHz bandpass (6 dB/octave rolloff) and then directly run into a 12 bit A-D converter on a Nova-3 minicomputer with a sampling rate of 50 #s/point. Averaged evoked responses were taken from each of the X, Y and Z inputs and stored in the computer memory separately. Five hundred samples were taken for each average, which was 10 ms in duration. These averages were individually plotted, and numerical values for each data bin were printed. We then used these numbers to make three-dimensional plots, which we constructed with yarn glued to data points located on fine fish line that was strung on specially drilled sheet-plastic supports. A zero voltage value for each of the plot axes (X, Y and Z) corresponded to the middle of the plot. In such a three-dimensional plot a single data point position represents the simultaneous values from three X, Y and Z recordings taken at a single time after the
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Fig. 1. Single channel ABR averages for orthogonal electrode pairs in the guinea pig. Z, vertexthroat; Y, mouth-nuchal ridge; X, pinna of stimulated ear-opposite pinna. All traces are shown with positivity of the first electrode pair up and are 10 ms in duration. The lettered points denote the boundaries of the first three waves, for comparison with Fig. 2. The right ear was stimulated.
183
Fig. 2. Stereoscopic photograph of a three-dimensional model showing the planar ABR of the data from Fig. 1. In this figure positive 'Z' is at the top of the illustration, positive 'Y' is away from the viewer, into the page, and positive 'X' is to the viewer's left. The easiest way to view the model threedimensionally is by using any of a number of commercially available stereoscopic viewers. If commercial viewers are not available, the reader may insert a 4--6 in. high card as a vertical barrier midway between the two figures. Then by coming within 6--7 in. of the illustration, the reader can adjust his own visual focus by staring into the distance until the three-dimensional effect is achieved. Focusing may be improved by moving nearer to or farther from the illustration. Notice that the continuous line from point A begins at the electrical origin (zero potential in all axes) and moves towards the viewer and to the upper right, then it changes direction to move away from the viewer and towards the lower left to point B. The points in the line between A and B appear to lie in a plane. Continuing from B the line again comes towards the viewer and to the upper right and then moves away from the viewer to point C. From this direction, the eye of the viewer is almost in the plane of these points. The line beginning at C moves vertically and away from the viewer and then drops to point D. Only the first of the ABR planes passes directly through the origin. Each plane has a unique orientation in this voltage-voltage-voltage space. stimulus. I n such a v o l t a g e - v o l t a g e - v o l t a g e plot, time is n o t explicitly g r a p h e d , b u t c a n be visualized as m o t i o n a l o n g the resulting t h r e e - d i m e n s i o n a l p l o t i f successive d a t a p o i n t s have differing voltages. I n d i v i d u a l v o l t a g e - t i m e plots for the X, Y a n d Z electrode pairs are shown in Fig. 1. These recordings show t h a t different X, Y a n d Z electrode pairs p r o v i d e different waveforms. I n s p e c t i o n o f the t h r e e - d i m e n s i o n a l m o d e l s revealed t h a t certain subsets o f sequential d a t a p o i n t s are planar, as shown in Fig. 2. A t least three subsets o f p o i n t s in the guinea pig t h r e e - d i m e n s i o n a l A B R lie in individual planes. The spatial p o s i t i o n o f each p l a n e differs significantly f r o m the others (Fig. 2) a n d r o u g h l y
184 corresponds to but is not fully matched to waves I to III in the guinea pig ABR as recorded from the vertex-mastoid electrode pair. No plane but the first passes through the origin (zero) of the three-dimensional plot. Similar results were seen in plots of recordings from all five animals. In vectorcardiography the data points of the cardiac potentials fall into distinct planes, which correspond with the P wave, QRS complex, and T wave 11. That planes should occur in three-dimensional far-field recordings with such different generators and locations as the heart and the ABR is a striking result, not evident from the singlechannel recordings in Fig. I. Planarity suggests that some underlying principle, such as synchrony and homogeneity of anatomical position of the generators, may play a role in the formation of the planes. Changes in the synchrony of the generator occur with cardiac lesions such as bundle branch block and myocardial infarction, with resulting alterations of the planarity of the waves of the vectorcardiogram2, 3,4,8. The three-dimensional ABR differs from the three-dimensional cardiac potential in that the ABR planes do not pass through the origin (Fig. 2). This is probably related to the fact that the ECG potentials return to the baseline before the next wave in the ECG (e.g. between the P wave and QRS complex), whereas the valleys of the ABR are not at zero potential. The purpose of this communication is to call attention to this previously undescribed phenomenon of planar points in the three-dimensional ABR and to suggest that these planes may be useful in analyzing and utilizing additional information obtainable from 'non-standard' electrode pairs. Furthermore, there is the possibility that this method can be utilized to distinguish the planar curve contributions of subsets of the neural generators of composite waveforms, with an attendant refining of interpretation of abnormal waveforms.
1 Buchwald, .I.S. and Huang, C. M., Far-field acoustic response: origins in the cat, Science, 189 (1975) 382-384. 2 DePasquale, N. and Burch, G. E., The spatial vectorcardiogram in left bundle branch block and myocardial infarction, with autopsy studies, Amer. J. Med,, 29 (1960) 633-639. 3 Frimpter, G. W., Scherr, L. and Ogden, D., The spatial vectorcardiogram in complete left bundle branch block with special reference to the initial component, Amer. Heart J., 55 (1958) 220-230. 4 Hugenholtz, P. G., Whipple, G. H. and Levine, H. D., A clinical appraisal of the vectorcardiogram in myocardial infarction. I. The cube system, Circulation, 24 (1961) 808-824. 5 Jewett, D. L., Volume-conducted potentials in response to auditory stimuli as detected by averaging in the cat, Electroenceph. clin. Neurophysiol., 28 (1970) 609-618. 6 Jewett, D. L. and Williston, J. S., Auditory-evoked far fields averaged from the scalp of humans, Brain, 94 (1971) 681-696. 7 Lev, A. and Sohmer, H., Sources of averaged neural responses recorded in animals and human subjects during cochlear audiometry (electro-cochleogram), Arch. klin. exp. Ohren- Nasen- Kehlkopfheilkd., 201 (1972) 79-90. 8 Mayer, J. W. Castellanos, A., Jr. and Lemberg, L., The spatial vectorcardiogram in peri-infarction block, Amer. J. Cardiol., 11 (1963) 613-621. 9 Picton, T. W., Hillyard, S. A., Krausz, H. I. and Galambos, R., Human auditory evoked potentials. I. Evaluation of components, Electroenceph. clin. Neurophysiol., 36 (1974) 179-190. 10 Plantz, R. G., Williston, J. S. and Jewett, D. L., Spatio-temporal distribution of auditory-evoked far field potentials in rat and cat, Brain Research, 68 (1974) 55-71. 11 Wartak, J., Simplified Vectorcardiography, J. B. Lippincott Co., Philadelphia, 1970, pp. 24-25.
181
Elsevier/North-Holland Biomedical Press
Planar curve analysis of three-channel auditory brain stem response: a preliminary report
J O H N S. WILLISTON, D O N L. JEWETT* and WILLIAM H. M A R T I N
Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA 94143 (U.S.A.) (Accepted July 2nd, 1981)
Key words: auditory brain stem response - - far-field - - three-dimensional - - neural generators - vectorcardiography - - planar curve - - evoked potentials - - mapping
Recordings of auditory brain stem responses (ABRs) were made in guinea pigs by means of farfield computer averaging from three orthogonal electrode pairs. The 'Y' locations were mouth and nuchal ridge, 'X' locations left and right mastoids, and 'Z' locations vertex and throat. Three-dimensional models were constructed to plot simultaneous points from the three averages in a voltage-voltage-voltage space. In all five animals tested, at least three subsets of sequential data points lie in separate planes. The data points in each plane roughly correspond to waves I to III in the guinea pig ABR as recorded from the vertex-throat electrode pair. The planarity of data points is a new observation and is not predicted from the singie-channel recordings. Three-dimensional planes are also found by means of vectorcardiography, which suggests some underlying principle, such as synchrony and homogeneity of anatomical position of the generators. Planar analysis of ABRs may be useful in analyzing and utilizing the additional information obtainable from 'non-standard' electrode pairs.
ABRs (Auditory Brainstem Responses) are far-field potentials that result from progressive activation of the auditory pathway in response to an abrupt auditory stimulus. ABRs are usually recorded between electrodes at the vertex and mastoid ipsilateral to the stimulus. A single averaged response plots voltage versus time and consists in humans of from five to seven waves within the first 10 ms after the stimulus ~,a. Various animal studies have supported the following generalizations: (1) sequential activation of different neural generators is represented in the ABR by a sequence of waves 1,5,7; (2) the potential at any given point in time after the stimulus is an algebraic summation of the potentials of all simultaneously active generatorsS; (3) small differences in electrode location do not significantly change the waveforms in such far-field recording6; and (4) large changes in electrode position can differentially accentuate or diminish different waves with or without phase differences10. The latter observation suggests that different far-field electrode pairs may yield different information concerning the neural generation of the ABR. * To whom correspondence should be addressed at: Special Studies Unit, Department of Orthopaedic Surgery, U-471, University of California, San Francisco, CA 94143 (U.S.A.). 0006-8993/81/0000-0000/$02.50 © Elsevier/North-Holland Biomedical Press
182 We have plotted the data points from three orthogonal pairs of electrodes in a three-dimensional plot and have observed a singular and striking result: certain segments of this plot are planar in configuration. The planarity of three-dimensional ABR data points is not predicted by single-channel ABR averages and may help to distinguish different neural generators that are simultaneously active. Five guinea pigs with normal ears as determined by examination and response to single-channel ABR were used as subjects and were lightly anesthetized with 2 %, halothane in oxygen administered via a face mask. Auditory 'clicks' of 200/~s duration and 60 dB SPL intensity from a T D H 39 earphone were presented monaurally to the right ear at 10 clicks/s through a plastic ear coupling tube that produced a 1 ms conduction delay. Hook-shaped electrodes fashioned from 26-gauge stainless steel hypodermic needles were attached to the scalp in three orthogonal pairs: the ' Y ' pair locations were mouth and nuchal ridge, ' X ' locations left and right mastoids, and 'Z' locations vertex and throat. The ground reference hook electrode was inserted in the skin of the back. Each input signal was amplified by a factor of 105 by a Data Inc. Model 2124 preamplifier with a 1-10 kHz bandpass (6 dB/octave rolloff) and then directly run into a 12 bit A-D converter on a Nova-3 minicomputer with a sampling rate of 50 #s/point. Averaged evoked responses were taken from each of the X, Y and Z inputs and stored in the computer memory separately. Five hundred samples were taken for each average, which was 10 ms in duration. These averages were individually plotted, and numerical values for each data bin were printed. We then used these numbers to make three-dimensional plots, which we constructed with yarn glued to data points located on fine fish line that was strung on specially drilled sheet-plastic supports. A zero voltage value for each of the plot axes (X, Y and Z) corresponded to the middle of the plot. In such a three-dimensional plot a single data point position represents the simultaneous values from three X, Y and Z recordings taken at a single time after the
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Fig. 1. Single channel ABR averages for orthogonal electrode pairs in the guinea pig. Z, vertexthroat; Y, mouth-nuchal ridge; X, pinna of stimulated ear-opposite pinna. All traces are shown with positivity of the first electrode pair up and are 10 ms in duration. The lettered points denote the boundaries of the first three waves, for comparison with Fig. 2. The right ear was stimulated.
183
Fig. 2. Stereoscopic photograph of a three-dimensional model showing the planar ABR of the data from Fig. 1. In this figure positive 'Z' is at the top of the illustration, positive 'Y' is away from the viewer, into the page, and positive 'X' is to the viewer's left. The easiest way to view the model threedimensionally is by using any of a number of commercially available stereoscopic viewers. If commercial viewers are not available, the reader may insert a 4--6 in. high card as a vertical barrier midway between the two figures. Then by coming within 6--7 in. of the illustration, the reader can adjust his own visual focus by staring into the distance until the three-dimensional effect is achieved. Focusing may be improved by moving nearer to or farther from the illustration. Notice that the continuous line from point A begins at the electrical origin (zero potential in all axes) and moves towards the viewer and to the upper right, then it changes direction to move away from the viewer and towards the lower left to point B. The points in the line between A and B appear to lie in a plane. Continuing from B the line again comes towards the viewer and to the upper right and then moves away from the viewer to point C. From this direction, the eye of the viewer is almost in the plane of these points. The line beginning at C moves vertically and away from the viewer and then drops to point D. Only the first of the ABR planes passes directly through the origin. Each plane has a unique orientation in this voltage-voltage-voltage space. stimulus. I n such a v o l t a g e - v o l t a g e - v o l t a g e plot, time is n o t explicitly g r a p h e d , b u t c a n be visualized as m o t i o n a l o n g the resulting t h r e e - d i m e n s i o n a l p l o t i f successive d a t a p o i n t s have differing voltages. I n d i v i d u a l v o l t a g e - t i m e plots for the X, Y a n d Z electrode pairs are shown in Fig. 1. These recordings show t h a t different X, Y a n d Z electrode pairs p r o v i d e different waveforms. I n s p e c t i o n o f the t h r e e - d i m e n s i o n a l m o d e l s revealed t h a t certain subsets o f sequential d a t a p o i n t s are planar, as shown in Fig. 2. A t least three subsets o f p o i n t s in the guinea pig t h r e e - d i m e n s i o n a l A B R lie in individual planes. The spatial p o s i t i o n o f each p l a n e differs significantly f r o m the others (Fig. 2) a n d r o u g h l y
184 corresponds to but is not fully matched to waves I to III in the guinea pig ABR as recorded from the vertex-mastoid electrode pair. No plane but the first passes through the origin (zero) of the three-dimensional plot. Similar results were seen in plots of recordings from all five animals. In vectorcardiography the data points of the cardiac potentials fall into distinct planes, which correspond with the P wave, QRS complex, and T wave 11. That planes should occur in three-dimensional far-field recordings with such different generators and locations as the heart and the ABR is a striking result, not evident from the singlechannel recordings in Fig. I. Planarity suggests that some underlying principle, such as synchrony and homogeneity of anatomical position of the generators, may play a role in the formation of the planes. Changes in the synchrony of the generator occur with cardiac lesions such as bundle branch block and myocardial infarction, with resulting alterations of the planarity of the waves of the vectorcardiogram2, 3,4,8. The three-dimensional ABR differs from the three-dimensional cardiac potential in that the ABR planes do not pass through the origin (Fig. 2). This is probably related to the fact that the ECG potentials return to the baseline before the next wave in the ECG (e.g. between the P wave and QRS complex), whereas the valleys of the ABR are not at zero potential. The purpose of this communication is to call attention to this previously undescribed phenomenon of planar points in the three-dimensional ABR and to suggest that these planes may be useful in analyzing and utilizing additional information obtainable from 'non-standard' electrode pairs. Furthermore, there is the possibility that this method can be utilized to distinguish the planar curve contributions of subsets of the neural generators of composite waveforms, with an attendant refining of interpretation of abnormal waveforms.
1 Buchwald, .I.S. and Huang, C. M., Far-field acoustic response: origins in the cat, Science, 189 (1975) 382-384. 2 DePasquale, N. and Burch, G. E., The spatial vectorcardiogram in left bundle branch block and myocardial infarction, with autopsy studies, Amer. J. Med,, 29 (1960) 633-639. 3 Frimpter, G. W., Scherr, L. and Ogden, D., The spatial vectorcardiogram in complete left bundle branch block with special reference to the initial component, Amer. Heart J., 55 (1958) 220-230. 4 Hugenholtz, P. G., Whipple, G. H. and Levine, H. D., A clinical appraisal of the vectorcardiogram in myocardial infarction. I. The cube system, Circulation, 24 (1961) 808-824. 5 Jewett, D. L., Volume-conducted potentials in response to auditory stimuli as detected by averaging in the cat, Electroenceph. clin. Neurophysiol., 28 (1970) 609-618. 6 Jewett, D. L. and Williston, J. S., Auditory-evoked far fields averaged from the scalp of humans, Brain, 94 (1971) 681-696. 7 Lev, A. and Sohmer, H., Sources of averaged neural responses recorded in animals and human subjects during cochlear audiometry (electro-cochleogram), Arch. klin. exp. Ohren- Nasen- Kehlkopfheilkd., 201 (1972) 79-90. 8 Mayer, J. W. Castellanos, A., Jr. and Lemberg, L., The spatial vectorcardiogram in peri-infarction block, Amer. J. Cardiol., 11 (1963) 613-621. 9 Picton, T. W., Hillyard, S. A., Krausz, H. I. and Galambos, R., Human auditory evoked potentials. I. Evaluation of components, Electroenceph. clin. Neurophysiol., 36 (1974) 179-190. 10 Plantz, R. G., Williston, J. S. and Jewett, D. L., Spatio-temporal distribution of auditory-evoked far field potentials in rat and cat, Brain Research, 68 (1974) 55-71. 11 Wartak, J., Simplified Vectorcardiography, J. B. Lippincott Co., Philadelphia, 1970, pp. 24-25.