Chromatic contrast thresholds may be estimated from transient VEPs by measuring the peak-to-peak amplitude at a range of stimulus levels followed by extrapolation to zero amplitude. However, there have been reports of failure of this technique when applied to the transient chromatic VEP due to variability of amplitude, difficulties with component identification and poor correlation of amplitude...

This study deals with the effect of stimulus contrast, between 1.3% and 96%, on the visual evoked potentials (VEPs) for onset of motion and for pattern reversal of checkerboard stimuli. The VEPs for pattern reversal and for the onset of motion both contain an initial positive peak (P1; peak latency about 120 msec) followed by a later negative peak (N2; peak latency 160-200 msec). However the P1...

The intersubject and intrasubject reproducibility of the VEP was evaluated using two different methods of producing pattern reversal--a mirror/projector system and a light-emitting diode (LED) system. Intersubject reproducibility was determined in 100 normal subjects (50 males, 50 females). Ten subjects were studied on ten different occasions over 11 months to establish intrasubject reproducibi...

Pattern reversal visual evoked potentials (VEPs) have been elicited in 16 female hyperthyroid patients before and after treatment and compared with those from a similar group of age and sex matched control subjects. No effect on latency was seen, and although larger amplitude values were noted in the thyrotoxic group these too were not significant. We would conclude that hyperthyroidism per se ...

In five subjects, we measured visual evoked potentials (VEPs) elicited by Vernier targets in which the contrast of the two components of the stimuli were modulated by sinusoids at distinct frequencies fl and f2. This approach allows for the extraction of VEP signatures of spatial interactions, namely, responses at intermodulation frequencies n1f1 + n2f2, without the need to introduce motion int...

The possibility of a link between medial axes (hereafter called symmetries) and figure salience has recently been proposed [Vision Res. 38 (1998) 2323; Vision Res. 38 (1998) 2429]. In this paper we investigated the characteristics of transient visual evoked potentials (VEPs) associated with stimulus figures designed to have different symmetries. Significant trends were observed for VEP componen...

Reliable motion-onset visual evoked potentials (result of the dorsal stream activation) were recorded to motion stimuli with the temporal frequency of five cycles per seconds in 20 different locations with eccentricity up to 42 degrees to periphery of the visual field. Amplitudes and latencies of the positive-negative-positive (P1-N1-P2; 84-144-208 ms) complex were evaluated in occipital (OZ an...

Abstract Background: Opium-dependence having different effects on the nervous system is a common problem, especially in the Middle East and Iran. The aim of this study is evaluating the effects of opium-dependence on visual evoked potential (VEP) in men. Methods: Thirty subjects with both chronic cigarette smoking and opium-dependence (group 1) and 30 subjects with only chronic ciga...

Faster and less obtrusive means for measuring a Visual Evoked Potential would be valuable in clinical testing and basic neuroscience research. This study presents a method for accomplishing this by smoothly modulating the luminance of a visual stimulus using a stochastic process. Despite its visually unobtrusive nature, the rich statistical structure of the stimulus enables rapid estimation of ...