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Zaaroor M, Bleich N, Mittelman N, Pratt H. Equivalent dipoles of the binaural interaction components and their comparison with binaurally evoked human auditory 40 Hz steady-state evoked potentials. Ear Hear 2003; 24:248-56. [PMID: 12799547 DOI: 10.1097/01.aud.0000070162.03279.79] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The purpose of this study was to acquire the Binaural Interaction (BI) components of the auditory middle-latency steady-state 40 Hz potentials, compare them with those of the binaurally evoked 40 Hz response and with transient-evoked Auditory Middle Latency Evoked Potentials (AMEP) and suggest possible contributors and generators of the composite 40 Hz BI. METHODS Potentials were recorded from 15 normal-hearing adults in response to 40/sec clicks. BI was derived by subtracting the binaurally evoked potentials from the algebraic sum of the evoked potentials to left and to right ear stimulation. Latencies, magnitudes and orientations of the dipole equivalents of 40 Hz components were compared with their BI counterparts, as estimated by three-channel Lissajous' trajectories. Comparison of the transient AMEP to binaural stimulation with the BI of the steady-state 40 Hz response was also conducted to elucidate the contributions of different levels along the auditory pathway to the 40 Hz BI responses. RESULTS Each cycle of the BI of the steady-state 40 Hz AMEP included four components that corresponded in latency, amplitude, and dipole orientation to their counterparts in the binaurally evoked waveform. Amplitudes of BI components were 50 to 60% of the respective values in the binaurally evoked potentials. Orientations of BI components matched those of the cortical components in the transient-evoked AMEP. CONCLUSIONS The results suggest that the main contribution to the 40 Hz BI is from rate resistant thalamo-cortical neurons. The results also suggest that the binaural cortical neurons contributing to the 40 Hz BI are less affected by increased rate than monaural neurons.
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Affiliation(s)
- Menashe Zaaroor
- Evoked Potentials Laboratory, Technion - Israel Institute of Technology, Haifa 32000, Israel.
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2
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Polyakov A, Pratt H. Electrophysiological correlates of azimuth and elevation cues for sound localization in human middle latency auditory evoked potentials. Ear Hear 2003; 24:143-55. [PMID: 12677111 DOI: 10.1097/01.aud.0000058109.44006.47] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To study, in humans, the effects of sound source azimuth and elevation on primary auditory cortex binaural activity associated with sound localization. DESIGN Middle Latency Auditory Evoked Potentials (MLAEPs) were recorded from three channels, in response to alternating polarity clicks, presented at a rate of 5/sec, at nine virtual spatial locations with different azimuths and elevations. Equivalent dipoles of Binaural Interaction Components (BICs) of MLAEPs were derived from 15 normally and symmetrically hearing adults by subtracting the response to binaural clicks at each spatial location from the algebraic sum of responses to stimulation of each ear alone. The amplified potentials were averaged over 4000 repetitions using a dwell time of 78 micro sec/address/channel. Variations in magnitudes, latencies and orientations of the dipole equivalents of cortical activity were noted in response to the nine spatial locations. RESULTS Middle-latency BICs included six major components corresponding in latency to the vertex-neck recorded components of MLAEP. A significant decrease of equivalent dipole magnitude was observed for two of the components: Pa2 in response to clicks in the backward positions (medium and no elevation); and Nb in response to clicks in the back and front positions (medium and no elevation) in the midsagittal plane. In the coronal plane, Pa2 equivalent dipole magnitude significantly decreased in response to right-horizontal (no elevation) clicks. Significant effects on equivalent dipole latencies of Pa2 were found for backward positions (no elevation) in the midsagittal plane. No significant effects on Pa2 and Nb equivalent dipole orientations were found across stimulus conditions. CONCLUSIONS The changes in equivalent dipole magnitudes and latencies of MLAEP BICs across stimulus conditions may reflect spectral tuning in binaural primary auditory cortex neurons processing the frequency cues for sound localization.
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Affiliation(s)
- Andrey Polyakov
- Evoked Potentials Laboratory, Technion--Israel Institute of Technology, Haifa
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Polyakov A, Pratt H. Electrophysiologic correlates of direction and elevation cues for sound localization in the human brainstem. Int J Audiol 2003; 42:140-51. [PMID: 12705779 DOI: 10.3109/14992020309090423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Our objective was to study the effects of sound source direction and elevation on human brainstem electrical activity associated with sound localization. The subjects comprised 15 normal-hearing and symmetrically hearing adults Auditory brainstem evoked potentials (ABEPs) were recorded from three channels, in response to alternating-polarity clicks, presented at a rate of 21.1/s, at nine virtual spatial locations with different direction and elevation attributes Equivalent dipoles of the binaural interaction components (BICs) of ABEPs were derived by subtracting the response to binaural clicks at each spatial location from the algebraic sum of monaural responses to stimulation of each ear in turn. The BICs included two major components corresponding in latency to the vertex-neck-recorded components V and VI of ABEP. A significant decrease of the first BIC's equivalent dipole magnitude was observed for clicks in the horizontal-frontal position (no elevation) in the midsagittal plane, and for clicks in the left-horizontal (no elevation) and right diagonally above the head (medium elevation) positions in the coronal plane, compared to clicks positioned directly above the head. Significant effects on equivalent dipole latencies of this component were found for front-back positions in the midsagittal plane and left-right positions in the coronal plane, compared to clicks positioned directly above the head. The most remarkable finding was a significant change in equivalent dipole orientations across stimulus conditions. We conclude that the changes in BIC equivalent dipole latency, amplitude and orientation across stimulus conditions reflect differences in the distribution of binaural pontine activity evoked by sounds in different spatial locations.
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Affiliation(s)
- Andrey Polyakov
- Evoked Potentials Laboratory, Technion-Israel Institute of Technology, Haifa, Israel
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4
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Pratt H, Karim N, Bleich N, Mittelman N. Short latency visual evoked potentials in occupational exposure to organic solvents. Neurophysiol Clin 2000; 30:306-12. [PMID: 11126642 DOI: 10.1016/s0987-7053(00)00230-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
OBJECTIVES Short latency visual evoked potentials (SVEP), in response to high-intensity flashes from light emitting diodes (LED), were used to detect subclinical effects along the visual pathway in four groups of subjects with different levels of exposure to gasoline, all within legally acceptable limits. METHODS Potentials and exposure levels were obtained from 31 subjects with different occupational exposure levels to gasoline fumes, as well as from 17 non-exposed control subjects. SVEP were recorded from four electrode sites (infra-orbital, Cz, Pz, Oz), in response to flashes presented to each eye in turn from goggle-mounted LEDs. SVEP components were defined after digital filtering, which eliminated the high-frequency oscillatory potentials and accentuated five major components: a periocular P30, attributed to the retina; a fronto-central N50, attributed to the optic nerve; centro-parietal P65 and N85, attributed to the optic tracts and radiation; and an occipital, cortical P105. RESULTS The latencies of successive SVEP components of the exposed subjects showed a significant latency prolongation compared to controls, beginning with activity attributed to the optic nerve and increasing cumulatively with the later components. Retinal components were not affected by the exposure to organic solvents. Among the exposed groups, differences in latency prolongation corresponded to occupational exposure. CONCLUSION The low-frequency components of SVEP were reliably measured and proved to be sensitive to subclinical effects of organic solvents on conduction along the visual pathway. These components are likely to be sensitive to other subcortical visual pathway lesions, but their clinical promise needs further verification.
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Affiliation(s)
- H Pratt
- Evoked Potentials Laboratory, Behavioral Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
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5
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Coutin-Churchman P, Charroo L, Balmaseda A, Santiesteban R. Vector analysis of visual evoked potentials elicited by pattern reversal and photic stimuli. Clin Neurophysiol 1999; 110:390-6. [PMID: 10363760 DOI: 10.1016/s1388-2457(98)00016-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The 2D VEPs to pattern reversal (PR) and LED goggle were studied in order to obtain a stable parameter for the functional assessing of posterior visual pathways regardless of the stimulus type used. DESIGN AND METHODS Apex c latency, bc segment amplitude (V), and bc vector orientation angle (theta) in voltage space were computed from VEPs recorded in 50 normal human beings and two patients with left posterior brain lesions, in an orthogonal Fpz-Oz and T3-T4 montage and displayed as a two channel Lissajous' trajectory. The effects of stimulus type and stimulated eye were analyzed in the normal group by a two-way ANOVA. RESULTS The stimulated eye had no effect on any parameter. Apex c latency was slightly longer, and V was greater and more variable in the responses to goggle stimuli, but there was no significant difference in theta, oriented to mid-occipital scalp with very low variability for both stimulus types. The patients showed significant deviations of theta towards the affected hemisphere. CONCLUSIONS The bc vector orientation (theta) is a stable parameter for the evaluation of the posterior visual pathways using both pattern reversal and LED stimuli, specially the latter, useful in unconscious or uncooperative patients.
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Affiliation(s)
- P Coutin-Churchman
- Department of Clinical Neurophysiology, Institute of Neurology and Neurosurgery, Havana, Cuba.
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Pratt H, Polyakov A, Aharonson V, Korczyn AD, Tadmor R, Fullerton BC, Levine RA, Furst M. Effects of localized pontine lesions on auditory brain-stem evoked potentials and binaural processing in humans. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1998; 108:511-20. [PMID: 9780022 DOI: 10.1016/s0168-5597(98)00029-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES AND METHODS Four sets of measurements were obtained from 11 patients (44-80 years old) with small, localized pontine lesions due to vascular disease: (1) Monaural auditory brain-stem evoked potentials (ABEPs; peaks I to VI); (2) Binaural ABEPs processed for their binaural interaction components (BICs) in the latency range of peaks IV to VI; (3) magnetic resonance imaging (MRI) of the brain-stem; and (4) psychoacoustics of interaural time disparity measures of binaural localization. ABEPs and BICs were analyzed for peak latencies and interpeak latency differences. Three-channel Lissajous' trajectories (3-CLTs) were derived for ABEPs and BICs and the latencies and orientations of the equivalent dipoles of ABEP and BICs were inferred from them. RESULTS Intercomponent latency measures of monaurally evoked ABEPs were abnormal in only 3 of the 11 patients. Consistent correlations between sites of lesion and neurophysiological abnormality were obtained in 9 of the 11 patients using 3-CLT measures of BICs. Six of the 11 patients had absence of one or more BIC components. Seven of the 11 had BICs orientation abnormality and 3 had latency abnormalities. Trapezoid body (TB) lesions (6 patients) were associated with an absent (two patients with ventral-caudal lesions) or abnormal (one patient with ventral-rostral lesions) dipole orientation of the first component (at the time of ABEPs IV), and sparing of this component with midline ventral TB lesions (two patients). A deviant orientation of the second BICs component (at the time of ABEPs V) was observed with ventral TB lesions. Psychoacoustic lateralization in these patients was biased toward the center. Rostral lateral lemniscus (LL) lesions (3 patients) were associated with absent (one patient) or abnormal (two patients) orientation of the third BICs component (at the time of ABEPs VI); and a side-biased lateralization with behavioral testing. CONCLUSIONS These results indicate that: (1) the BICs component occurring at the time of ABEPs peak IV is dependent on ventral-caudal TB integrity; (2) the ventral TB contributes to the BICs component at the time of ABEPs peak V; and (3) the rostral LL is a contributing generator of the BICs component occurring at the time of ABEP peak VI.
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Affiliation(s)
- H Pratt
- Evoked Potentials Laboratory, Behavioral Biology, Technion - Israel Institute of Technology, Haifa.
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7
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Abstract
Three-channel Lissajous' trajectories (3-CLT) of the binaural interaction (BI) in auditory brainstem evoked potentials (ABEP) were derived from 13 normally and symmetrically hearing adults by subtracting the response to binaural clicks from the algebraic sum of monaural responses. ABEPs were recorded from four channels, three of them orthonormal to each other, in response to alternating polarity clicks, presented at a rate of 11/s with interaural time differences (ITD) of 0.2, 0.4 and 1.0 ms and an intensity of 65 dB nHL, or isochronic to both ears with interaural intensity differences (IIDs) of 5, 10 and 15 dB (65 dB nHL +/- 2.5, 5.0 and 7.5 dB, respectively). All 3-CLTs included 6 planar segments (labeled BdI, BdII, BdIII, BeI, BeII and Bf). Amplitudes of 3-CLT BI components were not significantly affected by increasing ITDs and IIDs, but latencies of all components increased significantly. The most remarkable finding was a significant change in apex orientations of BeI and BeII of the BI 3-CLT across stimulus conditions. The changes in BeI and BeII apex orientations, across stimulus conditions, may reflect differences in the anatomical representation of activity evoked by differently lateralized sounds. We suggest that this may indicate spatio-topic organization in the human brainstem.
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Affiliation(s)
- A Polyakov
- Evoked Potentials Laboratory, Israel Institute of Technology, Haifa, Israel
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Pratt H, Bleich N, Martin WH. Short latency visual evoked potentials to flashes from light-emitting diodes. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1995; 96:502-8. [PMID: 7489671 DOI: 10.1016/0013-4694(95)00089-h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Short latency visual evoked potentials (SVEPs) have been described in response to high-intensity, strobe flashes. High-intensity flashes can now be generated from goggle-mounted light emitting diodes (LEDs) and the SVEPs to such flashes have been shown to be reproducible across subjects, avoiding photic spread to the examination room and acoustical artifacts from the strobe stimulator. In this study, SVEPs from multichannel records are described in terms of normative latencies and amplitudes, as well as scalp distributions, to explore their generators. Potentials were recorded from 10 young male subjects, from 16 scalp locations, in response to flashes from goggle-mounted LEDs. Flashes were presented to each eye in turn, as well as binocularly. The latencies, scalp distributions and intersubject variabilities of the LED evoked SVEPs were similar to those obtained with strobe flashes. SVEP components were divided into 3 groups, according to their latency and the electrodes at which they were recorded with the largest amplitudes: periocular (under 40 msec latency), fronto-central (40-55 msec) and parieto-occipital (55-80 msec latency). The scalp distributions observed in this study suggest subcortical generators along the visual pathway, beginning at the retina. The use of goggle-mounted LEDs should promote routine evaluation of the integrity of the visual pathway between retina and cortex using SVEPs.
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Affiliation(s)
- H Pratt
- Evoked Potentials Laboratory, Technion-Israel Institute of Technology, Haifa, Israel
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9
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Polyakov A, Pratt H. Three-channel Lissajous' trajectory of the binaural interaction components of human auditory middle-latency evoked potentials. Hear Res 1995; 82:205-15. [PMID: 7775286 DOI: 10.1016/0378-5955(94)00178-s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Three-channel Lissajous' trajectories (3-CLTs) of the binaural interaction component (BI) of auditory middle latency evoked potentials (AMLEPs) were derived from 14 normally hearing adults by subtracting the response to binaural clicks from the algebraic sum of monaural responses. AMLEPs were recorded in response to 65 dB nHL, rarefaction clicks, presented at a rate of 3.3/s. A normative set of BI 3-CLT measures was calculated and compared with the corresponding measures of simultaneously recorded, single-channel vertex-left mastoid and vertex-neck derivations of BI and of AMLEP to binaural stimulation (B). 3-CLT measures included: apex latency, amplitude and orientation, as well as planar segment duration, orientation, size and shape. The results showed seven main apices and associated planar segments ('Be', 'Bf', 'Bg', 'Bh', 'Bi1', 'Bi2' and 'Bj') in the 3-CLT of BI. Apex latencies of the BI 3-CLT were comparable to peak latencies of the vertex-left mastoid and vertex-neck AMLEP and BI records, both in their absolute values and in intersubject variability. Durations of BI planar segments were approximately 5.0 ms. Apex amplitudes of BI 3-CLT were larger than the respective peak amplitudes of the vertex-mastoid and vertex-neck BI records, while their intersubject variabilities were comparable. The lateralization of BI components may indicate asymmetric processing of binaural auditory input, or may be connected with anatomical asymmetry such as skull thickness. Preliminary analyses did not reveal a clear correlation between the lateralization of the BI component 'Bi2' and the handedness of the subject. We suggest that BI components of AMLEP may be associated with the primary auditory cortex and subcortical ascending structures.
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Affiliation(s)
- A Polyakov
- Evoked Potentials Laboratory Technion, Israel Institute of Technology, Haifa
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10
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Pratt H, Martin WH, Bleich N, Zaaroor M, Schacham SE. A high-intensity, goggle-mounted flash stimulator for short-latency visual evoked potentials. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1994; 92:469-72. [PMID: 7523092 DOI: 10.1016/0168-5597(94)90025-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The few studies that have been done on short-latency, subcortical visual evoked potentials (SVEPs) have all used stroboscopic flashes as the evoking stimulus. The dimensions of the stimulator, the acoustical artifacts and the photic spread to the examination room limited the use of SVEPs to research laboratories. With the advent of high-efficiency light-emitting diodes (LEDs), high-intensity flashes can now be generated from goggle-mounted LEDs. In this study, a goggle-mounted high-intensity stimulator was constructed and its flashes used to evoke SVEPs. The reproducibility of SVEPs across subjects and the ease of using the high-intensity LED flash stimulator make them a promising candidate for testing subcortical visual pathway function in the operating room.
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Affiliation(s)
- H Pratt
- Evoked Potentials Laboratory, Technion-Israel Institute of Technology, Haifa
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11
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Sjöström A, Abrahamsson M. Patterned light flash evoked short latency activity in the visual system of visually normal and in amblyopic subjects. Acta Ophthalmol 1994; 72:195-202. [PMID: 8079625 DOI: 10.1111/j.1755-3768.1994.tb05016.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In a previous experimental study on anaesthetized cat it was shown that a short latency (35-40 ms) cortical potential changed polarity due to the presence or absence of a pattern in the flash stimulus. The results suggested one pathway of neuronal activation in the cortex to a pattern that was within the level of resolution and another to patterns that were not. It was implied that a similar difference in impulse transmission to pattern and non-pattern stimuli may be recorded in humans. The present paper describes recordings of the short-latency visual evoked response to varying light flash checkerboard pattern stimuli of high intensity in visually normal and amblyopic children and adults. When stimulating the normal eye a visual evoked response potential with a peak latency between 35 to 40 ms showed a polarity change to patterned compared to non-patterned stimulation. The visual evoked response resolution limit could be correlated to a visual acuity of 0.5 and below. In amblyopic eyes the shift in polarity was recorded at the acuity limit level. The latency of the pattern depending potential was increased in patients with amblyopia compared to normal, but not directly related to amblyopic degree. It is concluded that the short latency, visual evoked response that mainly represents the retino-geniculo-cortical activation may be used to estimate visual resolution below 0.5 in acuity level.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Sjöström
- Department of Opthalmology, Sahlgren's Hospital, University of Gothenburg, Sweden
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12
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Schroeder CE, Tenke CE, Givre SJ. Subcortical contributions to the surface-recorded flash-VEP in the awake macaque. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1992; 84:219-31. [PMID: 1375881 DOI: 10.1016/0168-5597(92)90003-t] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Epidural mapping of flash-VEP in awake monkeys revealed a reliable, short latency negativity, N25 (onset: 18-22 msec; peak: 23-27 msec; duration: 15-20 msec), with a broad frontal surface distribution (frontolateral maximum). N25 was dissociable from the electroretinogram (ERG), from cortical VEP and from the high frequency oscillations (wavelets) coextensive with the ERG and with cortical VEP. Depth recordings traced N25 from its surface maximum down to the lateral geniculate nucleus (LGN). Concomitant VEP, current source density (CSD) and multiunit activity (MUA) profiles obtained with multicontact electrodes showed that the peak and later portion of N25 arise primarily from current sinks (associated with MUA increases) that reflect transmembrane current flow attending depolarization of cells in lamina 6, the uppermost lamina, but may also receive contributions from the more ventral LGN laminae. The initial portion of N25 arises from similar processes near the lamina 3/2 border. Wavelets, in contrast, are prominent in VEP, CSD and MUA within LGN, but attenuate rapidly above LGN. LGN laminar and cellular morphology predict volume conduction of N25 over a wide arc lateral and anterior to LGN and roughly horizontal isopotential planes medial and posterior to LGN. Recordings on the brain surface, within LGN, and in the regions surrounding LGN are consistent with these predictions. Possible contributions from other structures and how these results fit with data obtained in humans are considered.
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Affiliation(s)
- C E Schroeder
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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13
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Witt JC, Towle VL, Bolaños J, Spire JP. Tetrahedral recording of 3-D BAEPs: evidence for the centered dipole model. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1991; 80:551-60. [PMID: 1720732 DOI: 10.1016/0168-5597(91)90138-n] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Three-dimensional brain-stem auditory evoked potentials (3-D BAEPs) were recorded from 12 normal subjects using a new tetrahedral montage, as well as two other bipolar montages previously described for 3-channel Lissajous' trajectories (3-CLTs). Mean responses, as well as between-subject and within-subject variability were described. A mathematical transformation was applied to the recorded trajectories to render them in a common canonical form to test the assumption that the BAEP conforms to a centrally generated dipolar field. Apex, segment, and plane orientations were measured for each trajectory, and discrepancies between montages were evaluated to judge the adequacy of the centered dipole model. For the vector means of apices, segments, and planes, median angles of discrepancy between montages ranged from 10 to 23 degrees. These results support the validity of a centered dipole model for the BAEP and affirm the rationale for employing the 3-channel recording technique. Among the montages studied, the tetrahedron provided maximum economy by using fewer electrodes, avoided certain problematic recording sites, and produced less variable data.
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Affiliation(s)
- J C Witt
- Department of Neurology, Pritzker School of Medicine, University of Chicago, IL 60637
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14
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Towle VL, Witt JC, Ohira T, Munson R, Nader SH, Spire JP. Three-dimensional human pattern visual evoked potentials. I. Normal subjects. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1991; 80:329-38. [PMID: 1716556 DOI: 10.1016/0168-5597(91)90079-d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Pattern visual evoked potentials (PVEPs) were obtained from 30 normal adult volunteers, recording from both a conventional horizontal occipital array and three orthogonal bipolar antipodal channels approximating the three dimensions of space. Central and eccentric fixation of 60' checks and central fixation of 30' checks under binocular and monocular viewing conditions was employed. The three antipodal wave forms were displayed as a single 3-D Lissajous trajectory which contained four apices, corresponding to P40 (apex A), N70 (apex B), P100 (apex C) and N125 (apex D). The 3-D evoked potentials depicted the dynamic nature of the human PVEP in terms of changes in the 3-D voltage-voltage-voltage plots of the recordings. The orientation of the A-B, B-C and C-D curvilinear segments reflected the stimulating condition (central fixation vs. right vs. left hemi-field stimulation) for all subjects with more accuracy than did the wave forms from the conventional array. Spherical statistical methods are described for quantifying and evaluating 3-D evoked potential recordings.
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Affiliation(s)
- V L Towle
- Department of Neurology, University of Chicago, IL 60637
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15
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Thusneyapan S, Zahalak GI. A practical electrode-array myoprocessor for surface electromyography. IEEE Trans Biomed Eng 1989; 36:295-9. [PMID: 2917776 DOI: 10.1109/10.16479] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A new myoprocessor is described which produces a relatively smooth and accurate measure of a muscle's electrical activity during both slow and rapid movements. This is achieved partly by spatial averaging of weakly correlated EMG signals from electrodes distributed over the surface of the muscle.
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Towle VL, Brigell M, Spire JP. Hemi-field pattern visual evoked potentials: a comparison of display and analysis techniques. Brain Topogr 1989; 1:263-70. [PMID: 2641269 DOI: 10.1007/bf01129604] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Three methods for analyzing the spatial organization of visual evoked potentials were compared. Pattern reversal visual evoked potentials were obtained from a single subject under three viewing conditions: stimulation of the left, right, and both visual fields. The scalp distribution of the VEP to 1 deg checks was displayed using three recording and analysis techniques: a conventional horizontal occipital array of electrodes, topographic mapping, and 3-dimensional evoked potentials. All three techniques revealed "paradoxical" lateralization of P100. The relative merits of each technique are discussed.
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Affiliation(s)
- V L Towle
- Department of Neurology, University of Chicago, IL 60637
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17
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Towle VL, Munson R, Ohira T, Ivanovic L, Witt JC, Spire JP. Three-dimensional human somatosensory evoked potentials. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1988; 71:336-47. [PMID: 2457485 DOI: 10.1016/0168-5597(88)90036-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Median nerve somatosensory evoked potentials were recorded from 30 normal adults using conventional scalp derivations and an orthogonal bipolar surface electrode montage. This allowed the determination of the spatial orientation of the hypothetical centrally located equivalent dipole derived from the evoked response recorded in 3-dimensional voltage space. The 3-dimensional voltage trajectory describing changes in equivalent dipole orientation and magnitude revealed 4 major apices between 5 and 25 msec, 3 of which corresponded to the traditional P14, N20 and P25 peaks. A fourth apex at 17 msec was not as evident in the conventional recordings and signaled a transition from a vertical P14-N18 generator process to a horizontal N20 generator process. The normal within- and between-subject variability of trajectory apices, segments and planes are described, along with the theoretical and practical implications of this recording technique.
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Affiliation(s)
- V L Towle
- Department of Neurology, University of Chicago, IL 60637
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