PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7451076

Early wavelets in the VECP.

J B Siegfried·J Lukas
View original source ↗Export metadata ↓

Abstract

With the use of a Maxwellian view optical system to present light flashes to the right eye, electroretinograms (ERGs) and visual evoked cortical potentials (VECPs) were recorded from normal subjects. The first 120 msec postflash onset was examined. A series of five VECP wavelets was recorded with implicit times of 50, 72, 82, 90, and 101 msec, at the highest radiance used. Recordings of ERGs in the same experimental session revealed a series of three wavelets with implicit times of 23, 30, and 38 msec. It is concluded that the VECP wavelets are not volume-conducted from the retina and probably represent initial arrival of visual information at the cortex, or subcortical activity.

Explore related subjects

ElectroretinographyEvoked PotentialsHumansPhotic StimulationVisual PerceptionJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J B Siegfried, J Lukas. 1981. Early wavelets in the VECP.. https://pubmed.ncbi.nlm.nih.gov/7451076/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

The 'two global flash' mfERG in high and normal tension primary open-angle glaucoma.

PURPOSE: To analyse the sensitivity of the '2 global flash' multifocal electroretinogram (mfERG) to detect glaucomatous dysfunction in normal tension (NTG) and high tension primary open angle glaucoma (POAG) patients. METHODS: MfERGs were recorded from 20 NTG and 20 POAG patients and compared to those of 20 controls. The mfERG array consisted of 103 hexagons. Each m-sequence step started with a focal flash that could be either dark or light (m-sequence: 2--13, L(max): 200 cd/m(2), L(min): 1 cd/m(2)), followed by two global flashes (L(max): 200 cd/m(2)) at an interval of approximately 26 ms. Focal scalar products (SP) were calculated using focal templates derived from the control recordings (VERIS 4.8). We analyzed 5 response averages (central 7.5 degrees and 4 adjoining quadrants) of the response to the focal flash, the direct component at 10-40 ms (DC) and the following two components induced by the effects of the preceding focal flash on the response to the global flashes at 40-70 ms (IC-1) and at 70-100 ms (IC-2). RESULTS: Both NTG and POAG patients differed from controls in the IC-1 response to the superior quadrants, and POAG patients also differed from controls in the centre. The most sensitive parameter was the IC-1 of the superior temporal quadrant with an area under the ROC curve of 0.82 for POAG and 0.79 for NTG. The DC and the IC-2 did not differ significantly between the groups. When all five response averages of the IC-1 were taken into consideration 90% of the NTG patients and 85% of the POAG patients were correctly classified as abnormal while 80% of the control subjects were correctly classified as normal. CONCLUSIONS: This stimulus sequence holds promise for the diagnosis of early functional changes in POAG. A new finding is that both NTG, as well as POAG can be differentiated from control subjects.

Electroretinography↗
PubMed2006

Long-term effects of tibolone on ocular functions in postmenopausal women.

Hormone replacement therapy has been widely used for the prevention of postmenopausal osteoporosis and treatment of climacteric symptoms for many years, but its effect on ocular functions remains unclear. The aim of the study was to evaluate the long-term effects of tibolone on ocular functions in postmenopausal women. A total of 77 healthy women with at least 1 year of spontaneous menopause were enrolled in the study. Forty women were treated with tibolone for 6 months and 37 women were left untreated. All these patients underwent ophthalmic examination including visual acuity, intraocular pressure (IOP), tear functions, blue-on-yellow and white-on-white Humphrey visual field (HVF), visual evoked potentials (VEP) and electroretinography (ERG). There were significant differences in mean deviation of blue-on-yellow HVF, and oscillatory potentials (O1, O2, and O4) in the ERGs of the chronic tibolone users and the control (P < 0.0001, P = 0.001, P < 0.0001 and 0.05, respectively). However, no significant differences were observed in visual acuity, IOP, tear functions, white-on-white HVF and VEP. We concluded that, although tibolone had no effects on visual acuity, IOP, tear functions and VEP, it might cause some early adverse effects on the electrophysiologic and structural characteristics of the retina, which are detected by these sensitive assays. Randomized placebo-controlled studies with larger groups are needed in future research.

Electroretinography↗
PubMed2006

Examination of short binary sequences for mfERG recording.

The mfERG, when first introduced by Erich Sutter used long sequences with short periods (approximately 15 ms) between steps (flashes). Since then a number of studies have introduced slower or modified sequences to emphasise Oscillatory Potentials (OPs), Optic Nerve Head Components (ONHC) or the s-wave. With this reduction in the rate of presentation many of the investigators have reduced the length of the sequence to allow a shorter recording period. This is also desirable for patient comfort and co-operation in diagnostic investigations. When reducing the length of the sequence there is a risk that it will be too short to ensure orthogonality of the first order component and all significant higher order components, particularly when a large number of areas (hexagons) are stimulated. This paper aims to verify that a short sequence (using the sequence used by the Roland Retiscan stimulating 19 hexagons) is capable of keeping responses of both first and higher orders separate for each stimulating area. The sequence was investigated by placing photodiodes connected to a Diagnosys Espion and then exported to Excel and MATLAB for analysis. It was determined that the sequences used were m-sequences length n = 9. The photodiode only responded to flashes of light so was unable to detect a correcting 0 at the end of sequence. The sequences driving each hexagon were then determined and found to be shifted 26 steps from each other. The correlation coefficients between all sequences was found to be -1/(2n -1). The sequences to decode the second order kernels were determined and the correlation coefficients between each of these sequences, and between these and the original sequences, were also -1/(2n -1). This work provides a mathematical validation of the use of short sequences for slow mfERG, and describes an empirical test method.

Electroretinography↗