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Murphy RJ, Godfrey K, Shaw AD, Muthukumaraswamy S, Sumner RL. Modulation of long-term potentiation following microdoses of LSD captured by thalamo-cortical modelling in a randomised, controlled trial. BMC Neurosci 2024; 25:7. [PMID: 38317077 PMCID: PMC10845757 DOI: 10.1186/s12868-024-00844-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 01/10/2024] [Indexed: 02/07/2024] Open
Abstract
BACKGROUND Microdosing psychedelics is a phenomenon with claimed cognitive benefits that are relatively untested clinically. Pre-clinically, psychedelics have demonstrated enhancing effects on neuroplasticity, which cannot be measured directly in humans, but may be indexed by non-invasive electroencephalography (EEG) paradigms. This study used a visual long-term potentiation (LTP) EEG paradigm to test the effects of microdosed lysergic acid diethylamide (LSD) on neural plasticity, both acutely while on the drug and cumulatively after microdosing every third day for six weeks. Healthy adult males (n = 80) completed the visual LTP paradigm at baseline, 2.5 h following a dose of 10 µg of LSD or inactive placebo, and 6 weeks later after taking 14 repeated microdoses. Visually induced LTP was used as indirect index of neural plasticity. Surface level event-related potential (ERPs) based analyses are presented alongside dynamic causal modelling of the source localised data using a generative thalamocortical model (TCM) of visual cortex to elucidate underlying synaptic circuitry. RESULTS Event-related potential (ERP) analyses of N1b and P2 components did not show evidence of changes in visually induced LTP by LSD either acutely or after 6 weeks of regular dosing. However modelling the complete timecourse of the ERP with the TCM demonstrated changes in laminar connectivity in primary visual cortex. This primarily included changes to self-gain and inhibitory input parameters acutely. Layer 2/3 to layer 5 excitatory connectivity was also different between LSD and placebo groups. After regular dosing only excitatory input from layer 2/3 into layer 5 and inhibitory input into layer 4 were different between groups. CONCLUSIONS Without modulation of the ERPs it is difficult to relate the findings to other studies visually inducing LTP. It also indicates the classic peak analysis may not be sensitive enough to demonstrate evidence for changes in LTP plasticity in humans at such low doses. The TCM provides a more sensitive approach to assessing changes to plasticity as differences in plasticity mediated laminar connectivity were found between the LSD and placebo groups. TRIAL REGISTRATION ANZCTR registration number ACTRN12621000436875; Registered 16/04/2021 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=381476 .
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Affiliation(s)
- Robin J Murphy
- School of Pharmacy, University of Auckland, Auckland, New Zealand.
| | - Kate Godfrey
- Centre for Psychedelic Research, Department of Psychiatry, Imperial College London, London, UK
| | | | | | - Rachael L Sumner
- School of Pharmacy, University of Auckland, Auckland, New Zealand
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Acharya D, Ruesch A, Schmitt S, Yang J, Smith MA, Kainerstorfer JM. Changes in neurovascular coupling with cerebral perfusion pressure indicate a link to cerebral autoregulation. J Cereb Blood Flow Metab 2022; 42:1247-1258. [PMID: 35078343 PMCID: PMC9207489 DOI: 10.1177/0271678x221076566] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cerebral autoregulation ensures a stable average blood supply to brain tissue across steady state cerebral perfusion pressure (CPP) levels. Neurovascular coupling, in turn, relies on sufficient blood flow to meet neuronal demands during activation. These mechanisms break down in pathologies where extreme levels of CPP can cause dysregulation in cerebral blood flow. Here, we experimentally tested the influence of changes in CPP on neurovascular coupling in a hydrocephalus-type non-human primate model (n = 3). We recorded local neural and vascular evoked responses to a checkerboard visual stimulus, non-invasively, using electroencephalography and near-infrared spectroscopy respectively. The evoked signals showed changes in various waveform features in the visual evoked potentials and the hemodynamic responses, with CPP. We further used these signals to fit for a hemodynamic response function (HRF) to describe neurovascular coupling. We estimated n = 26 distinct HRFs at a subset of CPP values ranging from 40-120 mmHg across all subjects. The HRFs, when compared to a subject dependent healthy baseline (CPP 70-90 mmHg) HRF, showed significant changes in shape with increasing CPP (ρCPP = -0.55, p-valueCPP = 0.0049). Our study provides preliminary experimental evidence on the relationship between neurovascular coupling and CPP changes, especially when beyond the limits of static autoregulation.
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Affiliation(s)
- Deepshikha Acharya
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Alexander Ruesch
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Samantha Schmitt
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.,Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Jason Yang
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Matthew A Smith
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.,Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Jana M Kainerstorfer
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.,Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
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Visual Evoked Potentials Used to Evaluate a Commercially Available Superabsorbent Polymer as a Cheap and Efficient Material for Preparation-Free Electrodes for Recording Electrical Potentials of the Human Visual Cortex. SENSORS 2019; 19:s19224890. [PMID: 31717510 PMCID: PMC6891557 DOI: 10.3390/s19224890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/03/2019] [Accepted: 11/07/2019] [Indexed: 12/31/2022]
Abstract
The aim of this study was to investigate the use of inexpensive and easy-to-use hydrogel “marble” electrodes for the recording of electrical potentials of the human visual cortex using visual evoked potentials (VEPs) as example. Top hat-shaped holders for the marble electrodes were developed with an electrode cap to acquire the signals. In 12 healthy volunteers, we compared the VEPs obtained with conventional gold-cup electrodes to those obtained with marble electrodes. Checkerboards of two check sizes—0.8° and 0.25°—were presented. Despite the higher impedance of the marble electrodes, the line noise could be completely removed by averaging 64 single traces, and VEPs could be recorded. Linear mixed-effect models using electrode type, stimulus, and recording duration revealed a statistically significant effect of the electrode type on only VEP N75 peak latency (mean ± SEM: 1.0 ± 1.2 ms) and amplitude (mean ± SEM: 0.8 ± 0.9 µV) The mean amplitudes of the delta, theta, alpha, beta, and gamma frequency bands of marble electrodes were statistically significantly different and, on average, 25% higher than those of gold-cup electrodes. However, the mean amplitudes showed a statistically significant strong correlation (Pearson’s r = 0.8). We therefore demonstrate the potential of the inexpensive and efficient hydrogel electrode to replace conventional gold-cup electrodes for the recording of VEPs and possibly other recordings from the human cortex.
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Wittevrongel B, Van Hulle MM. Frequency- and Phase Encoded SSVEP Using Spatiotemporal Beamforming. PLoS One 2016; 11:e0159988. [PMID: 27486801 PMCID: PMC4972379 DOI: 10.1371/journal.pone.0159988] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 06/03/2016] [Indexed: 11/22/2022] Open
Abstract
In brain-computer interfaces (BCIs) based on steady-state visual evoked potentials (SSVEPs) the number of selectable targets is rather limited when each target has its own stimulation frequency. One way to remedy this is by combining frequency- with phase encoding. We introduce a new multivariate spatiotemporal filter, based on Linearly Constrained Minimum Variance (LCMV) beamforming, for discriminating between frequency-phase encoded targets more accurately, even when using short signal lengths than with (extended) Canonical Correlation Analysis (CCA), which is traditionally posited for this stimulation paradigm.
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Affiliation(s)
| | - Marc M. Van Hulle
- Laboratory for Neuro- and Psychophysiology, K.U. Leuven, Leuven, Belgium
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Liu TT, Glover GH, Mueller BA, Greve DN, Brown GG. An introduction to normalization and calibration methods in functional MRI. PSYCHOMETRIKA 2013; 78:308-21. [PMID: 25107618 DOI: 10.1007/s11336-012-9309-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 02/15/2012] [Indexed: 05/26/2023]
Abstract
In functional magnetic resonance imaging (fMRI), the blood oxygenation level dependent (BOLD) signal is often interpreted as a measure of neural activity. However, because the BOLD signal reflects the complex interplay of neural, vascular, and metabolic processes, such an interpretation is not always valid. There is growing evidence that changes in the baseline neurovascular state can result in significant modulations of the BOLD signal that are independent of changes in neural activity. This paper introduces some of the normalization and calibration methods that have been proposed for making the BOLD signal a more accurate reflection of underlying brain activity for human fMRI studies.
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Affiliation(s)
- Thomas T Liu
- Center for Functional MRI, University of California San Diego, 9500 Gilman Drive, MC 0677, La Jolla, CA, 92093, USA,
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Chang HC, Lee PL, Lo MT, Lee IH, Yeh TK, Chang CY. Independence of Amplitude-Frequency and Phase Calibrations in an SSVEP-Based BCI Using Stepping Delay Flickering Sequences. IEEE Trans Neural Syst Rehabil Eng 2012; 20:305-12. [DOI: 10.1109/tnsre.2011.2180925] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Hsiang-Chih Chang
- Department of Electrical Engineering, National Central University, Jhongli 320, Taiwan.
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Wu HY, Lee PL, Chang HC, Hsieh JC. Accounting for phase drifts in SSVEP-based BCIs by means of biphasic stimulation. IEEE Trans Biomed Eng 2010; 58:1394-402. [PMID: 21193370 DOI: 10.1109/tbme.2010.2102757] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study proposes a novel biphasic stimulation technique to solve the issue of phase drifts in steady-state visual evoked potential (SSVEPs) in phase-tagged systems. Phase calibration was embedded in stimulus sequences using a biphasic flicker, which is driven by a sequence with alternating reference and phase-shift states. Nine subjects were recruited to participate in off-line and online tests. Signals were bandpass filtered and segmented by trigger signals into reference and phase-shift epochs. Frequency components of SSVEP in the reference and phase-shift epochs were extracted using the Fourier method with a 50% overlapped sliding window. The real and imaginary parts of the SSVEP frequency components were organized into complex vectors in each epoch. Hotelling's t-square test was used to determine the significances of nonzero mean vectors. The rejection of noisy data segments and the validation of gaze detections were made based on p values. The phase difference between the valid mean vectors of reference and phase-shift epochs was used to identify user's gazed targets in this system. Data showed an average information transfer rate of 44.55 and 38.21 bits/min in off-line and online tests, respectively.
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Affiliation(s)
- Hung-Yi Wu
- Institute of Brain Science, National Yang-Ming University, Taipei 112, Taiwan.
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Wu Z, Lai Y, Xia Y, Wu D, Yao D. Stimulator selection in SSVEP-based BCI. Med Eng Phys 2008; 30:1079-88. [DOI: 10.1016/j.medengphy.2008.01.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 12/29/2007] [Accepted: 01/28/2008] [Indexed: 10/22/2022]
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Friman O, Volosyak I, Gräser A. Multiple channel detection of steady-state visual evoked potentials for brain-computer interfaces. IEEE Trans Biomed Eng 2007; 54:742-50. [PMID: 17405382 DOI: 10.1109/tbme.2006.889160] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this paper, novel methods for detecting steady-state visual evoked potentials using multiple electroencephalogram (EEG) signals are presented. The methods are tailored for brain-computer interfacing, where fast and accurate detection is of vital importance for achieving high information transfer rates. High detection accuracy using short time segments is obtained by finding combinations of electrode signals that cancel strong interference signals in the EEG data. Data from a test group consisting of 10 subjects are used to evaluate the new methods and to compare them to standard techniques. Using 1-s signal segments, six different visual stimulation frequencies could be discriminated with an average classification accuracy of 84%. An additional advantage of the presented methodology is that it is fully online, i.e., no calibration data for noise estimation, feature extraction, or electrode selection is needed.
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Affiliation(s)
- Ola Friman
- Institute of Automation, University of Bremen, Otto-Hahn Allee 1, 28359 Bremen, Germany.
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Stephen JM, Ranken DF, Aine CJ. Frequency-Following and Connectivity of Different Visual Areas in Response to Contrast-Reversal Stimulation. Brain Topogr 2006; 18:257-72. [PMID: 16845594 DOI: 10.1007/s10548-006-0004-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2006] [Indexed: 11/28/2022]
Abstract
The sensitivity of visual areas to different temporal frequencies, as well as the functional connections between these areas, was examined using magnetoencephalography (MEG). Alternating circular sinusoids (0, 3.1, 8.7 and 14 Hz) were presented to foveal and peripheral locations in the visual field to target ventral and dorsal stream structures, respectively. It was hypothesized that higher temporal frequencies would preferentially activate dorsal stream structures. To determine the effect of frequency on the cortical response we analyzed the late time interval (220-770 ms) using a multi-dipole spatio-temporal analysis approach to provide source locations and timecourses for each condition. As an exploratory aspect, we performed cross-correlation analysis on the source timecourses to determine which sources responded similarly within conditions. Contrary to predictions, dorsal stream areas were not activated more frequently during high temporal frequency stimulation. However, across cortical sources the frequency-following response showed a difference, with significantly higher power at the second harmonic for the 3.1 and 8.7 Hz stimulation and at the first and second harmonics for the 14 Hz stimulation with this pattern seen robustly in area V1. Cross-correlations of the source timecourses showed that both low- and high-order visual areas, including dorsal and ventral stream areas, were significantly correlated in the late time interval. The results imply that frequency information is transferred to higher-order visual areas without translation. Despite the less complex waveforms seen in the late interval of time, the cross-correlation results show that visual, temporal and parietal cortical areas are intricately involved in late-interval visual processing.
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Affiliation(s)
- Julia M Stephen
- Department of Radiology, University of New Mexico School of Medicine, Albuquerque, NM 87131-0001, USA.
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11
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Tobimatsu S, Celesia GG. Studies of human visual pathophysiology with visual evoked potentials. Clin Neurophysiol 2006; 117:1414-33. [PMID: 16516551 DOI: 10.1016/j.clinph.2006.01.004] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 12/28/2005] [Accepted: 01/11/2006] [Indexed: 11/19/2022]
Abstract
Visual evoked potentials (VEPs) offer reproducible and quantitative data on the function of the visual pathways and the visual cortex. Pattern reversal VEPs to full-field stimulation are best suited to evaluate anterior visual pathways while hemi-field stimulation is most effective in the assessment of post-chiasmal function. However, visual information is processed simultaneously via multiple parallel channels and each channel constitutes a set of sequential processes. We outline the major parallel pathways of the visual system from the retina to the primary visual cortex and higher visual areas via lateral geniculate nucleus that receive visual input. There is no best method of stimulus selection, rather visual stimuli and VEPs' recording should be tailored to answer specific clinical and/or research questions. Newly developed techniques that can assess the functions of extrastriate as well as striate cortices are discussed. Finally, an algorithm of sequential steps to evaluate the various levels of visual processing is proposed and its clinical use revisited.
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Affiliation(s)
- Shozo Tobimatsu
- Department of Clinical Neurophysiology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan.
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Goto Y, Taniwaki T, Kinukawa N, Tobimatsu S. Interhemispheric functional synchronization at the first step of visual information processing in humans. Clin Neurophysiol 2004; 115:1409-16. [PMID: 15134709 DOI: 10.1016/j.clinph.2004.01.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2004] [Indexed: 11/15/2022]
Abstract
OBJECTIVE We examined the interhemispheric functional synchronization of the visual cortex using coherence (Coh) analysis. METHODS Achromatic or isoluminant chromatic sinusoidal grating stimuli were presented to each hemifield at a rate of 8 reversals/s to record steady-state visual-evoked potentials (S-VEPs) in 10 healthy subjects. Four recording electrodes were placed at O1, O2, P3 and P4, referred to an electrode at Cz. A total of 50 responses of 1 s epoch were averaged, and were subjected to discrete fast Fourier transforms to yield the amplitude and phase of the 8 Hz component. Ordinary and partial Coh values were also calculated. RESULTS For both achromatic and chromatic stimuli, the 8 Hz amplitudes of O1 and O2 were significantly larger than those of P3 and P4 without any significant difference between O1 and O2. The phase lag between O1 and O2 was approximately 30 degrees (latency shift 10.4 ms). Partial Coh between O1 and O2 at 8 Hz was significantly greater than that of the unstimulated condition, and this was only observed at 8 Hz. CONCLUSIONS These results suggest that interhemispheric synchronization in the occipital area occurs despite the nature of the visual stimuli. Therefore, the activation of interhemispheric connection is important for the early stage of the visual information processing. SIGNIFICANCE Our results indicate that the first step of the visual information processing requires interhemispheric functional synchronization.
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Affiliation(s)
- Yoshinobu Goto
- Department of Clinical Neurophysiology, Neurological Institute, Graduate School of Medical Sciences, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan.
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Abstract
OBJECTIVE To determine whether a one-dimensional (1D) Laplacian analysis detects steady-state visual evoked potentials (ssVEPs) faster than the standard O(z)-F(z) montage and to establish the optimum position of Laplacian reference electrodes. METHODS Twenty-two normal adults were shown reversing checks ranging from 1.5' to 60'. Three electrode montages were investigated: O(z)-F(z), LO-F(z) and a 1D Laplacian analysis of 3 occipital electrodes (2O(z)-(RO+LO)). RO and LO were placed symmetrically and horizontally about O(z). Five different locations for RO and LO were investigated. Recordings were analysed in the frequency domain and the presence (and detection time, DT) or absence of a ssVEP defined statistically. Effects of individual, reference electrode site and check size on DT and phase differences between recording montages were investigated. RESULTS Laplacian analysis detected ssVEPs to small (3') checks faster than O(z)-F(z), by 12.3 and 4.1s on average with Laplacian reference electrodes at 15 and 20% of half-head circumference, respectively. The optimum position of reference electrodes was governed by the instantaneous spatial spread of the response and the noise coherence between midline and lateral electrodes. CONCLUSIONS A 1D Laplacian analysis can reduce the time to statistical detection of ssVEPs compared to the traditional O(z)-F(z) recording for stimuli near the normal acuity threshold of adults. This in turn could be used to minimise the length of a VEP acuity assessment.
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Affiliation(s)
- Alison M Mackay
- Department of Clinical Physics, Yorkhill NHS Trust, Dalnair Street, G3 8SJ, Glasgow, UK.
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Tobimatsu S, Zhang YM, Kato M. Steady-state vibration somatosensory evoked potentials: physiological characteristics and tuning function. Clin Neurophysiol 1999; 110:1953-8. [PMID: 10576493 DOI: 10.1016/s1388-2457(99)00146-7] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE The steady-state somatosensory evoked potentials (S-SEPs) to vibratory stimulation were recorded to characterize their physiological properties. METHODS Vibratory stimuli were applied to the right palmar surface in 10 normal subjects. A total of 200 responses were recorded from electrodes at 2 cm posterior to C3, Cz and C4 and 2 cm anterior to C3. All responses were Fourier analyzed and the amplitudes of the first (1F) and second (2F) harmonic components were thus obtained. The effects of modulation frequency (5-30 Hz) and stimulus intensity (0.001-0.1 Newton (N)) on S-SEPs were studied. RESULTS The amplitudes of 1F and 2F were greatest at the electrode 2 cm posterior to C3, 1F being predominant. The mean 1F amplitudes as a function of modulation frequency showed a bimodal distribution with a trough at 14 Hz and a peak at 21 Hz. The mean 1F amplitudes showed a linear increase of up to 0.05 N and thereafter reached a plateau against the logarithmic stimulus intensity axis. CONCLUSION Vibratory S-SEPs may originate from the primary somatosensory cortex and provide information on the fast-adapting mechanoreceptive afferents. The temporal resonance at 21 Hz places the somatosensory system between the visual and auditory systems.
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Affiliation(s)
- S Tobimatsu
- Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
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Tomoda Y, Tobimatsu S, Mitsudome A. Visual evoked potentials in school children: a comparative study of transient and steady-state methods with pattern reversal and flash stimulation. Clin Neurophysiol 1999; 110:97-102. [PMID: 10348327 DOI: 10.1016/s0168-5597(98)00051-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Flash visual evoked potentials (VEPs) are commonly used in pediatrics, because children are sometimes uncooperative. We performed a comparative study of transient and steady-state VEPs with pattern reversal (PR) and flash (light-emitting diode, LED) stimulation. METHODS We recorded VEPs in 15 boys and 17 girls (aged 6-12 years) using 4 different stimulus conditions. The latency and amplitude of transient VEPs (T-VEPs) were measured. Steady-state VEPs (S-VEPs) were Fourier analyzed, and both the phase and amplitude of the major components were obtained. RESULTS The mean P100 latency of LED T-VEPs was longer and had a greater variability than that of PR T-VEPs. The LED T-VEPs had an amplitude of about double that of PR T-VEPs. The first harmonic response in the LED and second harmonic in PR were the major components of S-VEPs. The phases of PR and LED S-VEPs had narrow angular dispersions and amplitudes showed marked intersubject variability. Sex and age had no significant effect on both T-VEPs and S-VEPs. CONCLUSIONS Reproducible VEPs with 4 stimulus conditions can be obtained in school children. T-VEPs and S-VEPs are clinically useful because these methods provide complementary information.
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Affiliation(s)
- Y Tomoda
- Department of Pediatrics, School of Medicine, Fukuoka University, Japan
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Lyskov E, Ponomarev V, Sandström M, Mild KH, Medvedev S. Steady-state visual evoked potentials to computer monitor flicker. Int J Psychophysiol 1998; 28:285-90. [PMID: 9545663 DOI: 10.1016/s0167-8760(97)00074-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the present study, steady-state visual evoked potentials (S-VEP) in response to amplitude-modulated light from a computer monitor (colour sVGA, 15-inch tube) have been examined. S-VEPs to computer monitors with different refresh rates (60 Hz or 72 Hz) and screen brightness (65 cd/m2 or 6 cd/m2) were recorded in 13 subjects with normal or corrected-to-normal vision. EEG samples were amplified, averaged and stored using Cadwell Excel EMG-EP recorder and a regression model was applied for the amplitude analysis. The mean values of S-VEP amplitude at 60 Hz were found to be significantly higher at 60 Hz refresh rate vs. 72 Hz (F1,12 = 14.1; P = 0.003). Effect of screen brightness (F2,24 = 6.5; e = 0.62; P = 0.00075) as well as the interaction effect of refresh rate and screen brightness (F2,24 = 11.6; P = 0.0003) were also found to be significant. Data obtained show that the characteristics of amplitude-modulated light from a computer monitor (frequency, brightness, waveform) are sufficient to elicit S-VEP, and the influence is not only restricted to the peripheral divisions of the visual system as it was shown earlier, but also extends to the central brain structures.
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Affiliation(s)
- E Lyskov
- Institute of the Human Brain, St. Petersburg, Russia
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Müller MM, Teder W, Hillyard SA. Magnetoencephalographic recording of steady-state visual evoked cortical activity. Brain Topogr 1997; 9:163-8. [PMID: 9104827 DOI: 10.1007/bf01190385] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Steady-state visual evoked magnetic fields (SSVEFs) were recorded in response to a flickering light source using a 37-channel magnetometer. The SSVEF had a sinusoidal waveform having the same fundamental frequency as the driving stimulus, which was either 6.0 Hz, 11.9 Hz, or 15.2 Hz. SSVEF topographies at each frequency had a dipoloar form over the posterior head that could well-modelled by single equivalent current dipoles. The best-fit dipoles were localized in posterior occipital cortex for the SSVEFs to 6.0 and 11.9 Hz stimuli and in more anterior and ventromedial occipital cortex for the 15.2 Hz SSVEP.
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Affiliation(s)
- M M Müller
- Department of Neurosciences, University of California, San Diego, La Jolla, USA.
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