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At least 1,351 records · Page 75Linked to original sources
PubMed1986

[Behavior of visual evoked potentials (pattern reversal VECP) in smokers].

Twenty six clinically healthy smokers were studied with transient pattern visual-evoked potentials. In comparison with a sample of "normal" subjects we found a difference of some parameters (P less than 0.05): the P2-latency and the interocular difference of latency on average were 6-7 ms respectively 2 ms larger. Thirteen subjects have had a prolonged P2-latency (P less than 0.05) and/or a difference in interocular latencies larger than 5 ms. These findings may suggest on subclinical disturbances of visual system and indicators of an special sensitivity of that person. The findings are possibly related to tobacco-alcohol amblyopia.

Adult↗
PubMed1985

[Latency differences of visual evoked potentials in binocular and monocular checkerboard stimulation as well as age and sex dependence].

Pattern reversal evoked potentials (VEPs) have been recorded in 100 normal subjects with an average age of 37.6 years (range 11-69). We found significantly shorter latencies of the P 100 for binocular stimulation compared to monocular stimulation. Women under 50 years showed shorter latencies than men for both binocular and monocular stimulation. Men showed no significant latency dependence of age. However, women had a significant latency prolongation above an age of 50 years, indicating a sex specific influence on latencies.

Adolescent↗
PubMed1983

Flicker threshold and pattern VEP latency in ocular hypertension and glaucoma.

Latency of the pattern visual-evoked potential (PVEP) was measured in 24 ocular hypertensive (OHT) patients, eight open-angle glaucoma (OAG) patients, and 37 control subjects. The PVEP stimulus was a 2.3 cycle/degree sinusoidal grating, counterphase-modulated at 1 Hz. Field size was 9 degrees and mean luminance 1.7 log ft-lamberts. For 22 of the 32 patients, a psycholphysical measure of dynamic contrast sensitivity at 8 Hz (DRC) was obtained with a 4 degrees diameter stimulus, by determining the mean value for the contrast sensitivities to a homogeneous flickering field and to a 1.2 cycle/degree counterphase-flickering grating. Patient DRC values were compared with previously published control data from 21 subjects. Mean PVEP latencies of both the OHT and the OAG patients were greater than normal (P less than 0.001), with the OAG value larger than the OHT value (P less than 0.001). Mean DRCs were lower than normal (P less than 0.002) for both patient groups, with the OAG value lower than the OHT value (P less than 0.025). DRC correlated with PVEP latency for these patients (r = -0.66, P less than 0.001).

Evoked Potentials, Visual↗
PubMed1983

Changes in spatial resolution for pattern and movement detection in clinical cases.

A simple and relatively fast method was used to evaluate visual performance: gratings of sinusoidal luminance profile, generated on the face of an oscilloscope, were reversed in contrast at a rate of 2 Hz. Under these conditions the patients could set separate contrast thresholds for seeing either the structure of a grating or its apparent movement. The grating resolution limit (maximum spatial frequency) for each task was determined by extrapolation from thresholds measured at several spatial frequencies. The resulting ratios of pattern/movement resolution limits (P:M) are usually between 1.6 and 2 for normals and for patients with pathological changes located distally (probably prior to the chiasma). On the other hand in patients suspected of multiple sclerosis the P:M ratios were reduced to below 1.3. It is considered that such results may suggest a central site for the damage, although they do not exclude pre-chiasmal defects which may occur simultaneously during the acute stages of the disease.

Adult↗
PubMed1981

Event-related brain potentials to human faces in infants.

Event-related brain potentials (ERPs) in response to tachistoscopically presented photographs of 2 human faces were recorded for 4--7-month-old infants. For each infant 1 face was chosen to be presented frequently (p = .88, a low-information event) and the other infrequently (p = .12, a high-information event). Both types of events elicited in our infants a long-latency negative ERP wave (ca. 700 msec), termed Nc, and a long-latency positive wave (ca. 1,360 msec), termed Pc. We found that the discrepant, infrequently presented face elicited Nc waves which were higher in amplitude and longer in latency than those elicited by the frequent face. These differences suggest that our infants were able to remember the frequently presented face from trial to trial and to discriminate it from the discrepant face. The discrepant event elicited Pc waves which were insignificantly higher in amplitude than those elicited by frequent events. In adults and children, discrepant events have been found by numerous researchers to elicit positive P3 waves (latency ca. 300--800 msec). In our study, however, such waves could not be discerned. So, of all of the ERP waves which have been related to cognitive processes, the wave which is maturationally the earliest to appear is the Nc wave, which has been related to the perception of attention-getting events or events of interest to the subject. Our findings suggest that ERP responses could provide a sensitive means for investigating infant cognitive development since they do not depend upon an integrated motor-response system.

Discrimination Learning↗
PubMed1994

[Objective evaluation of visual strain in computer screen and office work by recording visually evoked cortical potentials (VECP) and determining changes in contrast sensitivity and refraction].

Visual evoked cortical potentials (VECP) elicited with checkerboard pattern reversal stimuli of high spatial frequency and low contrast were recorded. The changes in the VECP depending on the duration of task-oriented activity at video display units (VDU) and in the office were determined. The testing procedure can be used to decide on adequate recovery periods (breaks) for any visual workload and requires only a short time. We investigated 30 probands: 10 subjects tested before and after 4 h of VDU work under controlled standard conditions had statistically significant increases of latency (P < 0.001) and decreases of amplitude in VECP recordings (P < 0.05). Another 10 subjects tested at the same intervals but exposed to standard office working conditions also showed statistically significant increases of latency (P < 0.0001) and decrease of amplitude in VECP recordings (P < 0.01). The 10 control subjects tested at the same intervals spent the time between recording sessions on leisure activity (walking) and showed no significant VECP changes. Statistical evaluation was performed with Student's t-test for paired samples. Contrast sensitivity (Ginsburg test) decreased in both VDU and office groups after completion of their workload, but remained within normal limits. The maximal changes in refraction amounted to +/- 0.25 D after 4 h and +/- 0.5 D after 6 h and showed no bias. Extended periods of working at VDUs and conventional office work increase the latency and decrease the amplitude of the pattern-evoked VECP. This method can be used to determine optimal scheduling of breaks in for people working at VDUs and doing conventional office work.

Adult↗