Visual evoked potentials (VEP's) recorded from the scalp are sensitive to retinal image sharpness and thus to changes in the refractive state of the eye. Initially the responses to checkerboard flash or reversal stimuli were computer-averaged in order to raise the signal above the noise, primarily the electroencephalogram (EEG). Recently analogue Fourier signal analysis has been proposed for us...

Brain-computer interfaces (BCIs), independent of the brain's normal output pathways, are attracting an increasing amount of attention as devices that extract neural information. As a typical type of BCI system, the steady-state visual evoked potential (SSVEP)-based BCIs possess a high signal-to-noise ratio and information transfer rate. However, the current high speed SSVEP-BCIs were implemente...

Although attention in older adults is an active research area, feature-selective aspects have not yet been explicitly studied. Here we report the results of an exploratory study involving directed changes in feature-selective attention. The stimuli used were two random dot kinematograms (RDKs) of different colours, superimposed and centrally presented. A colour cue with random onset after the b...

Emotional stimuli capture and hold attention without explicit instruction. The late positive potential (LPP) component of the event related potential can be used to track motivated attention toward emotional stimuli, and is larger for emotional compared to neutral pictures. In the frequency domain, the steady state visual evoked potential (ssVEP) has also been used to track attention to stimuli...

Differences in cortical geometry within and between subjects can complicate multifocal visual evoked potential (mfVEP) and standard evoked potential (EP) intra- and inter-subject comparisons. We present methods for aligning temporal intra- and inter-subject data prior to comparison. Multiple groups have informally observed that the two dominant temporal principal components (PCs) of the pattern...

The aim of this work is to introduce correlation test to detect artifacts in visual evoked potentials. If an artifact occurs a sample signal deviates from the ensemble average. In this paper signals with less correlation coefficient are considered as artifacts and are removed from the further analysis. An attempt has been made to apply these techniques to 14 -channel visual evoked potentials (V...

H. Drissi,1 F. Regragui,2 J-P. Antoine,3 and M. Benouna 1 1 D epartement de Physique, Facult e des Sciences et Techniques Tanger, Maroc 2 D epartement de Physique, Facult e des Sciences, Univ. Mohamed V Rabat, Maroc 3 Institut de Physique Th eorique, Universit e Catholique de Louvain B-1348 Louvain-la-Neuve, Belgium Abstract Visual Evoked Potentials are analyzed with the continuous wavelet tran...

Visually Evoked Potentials (VEPs) were recorded in response to the onset of chromatic and luminance motion gratings of 1 cpd and luminance 40 cd m(-2) subtending a 7 degrees field. At slow speeds (< or =2 cycles s(-1)) the motion onset response exhibits a clear amplitude minimum at isoluminance. Over the Michelson contrast range tested (0.05-0.75) the chromatic response at 2 cycles s(-1) posses...

PURPOSE To study the effect of monocular visual deprivation caused by dense unilateral cataracts in adults. METHODS Visual evoked potentials have been recorded in 11 patients after removal of a dense unilateral cataract acquired in adulthood. These were compared with those from 8 control patients after removal of a mild lens opacity. RESULTS Visual evoked potentials recorded on the first da...

Multifocal visual evoked potentials (mfVEP) were recorded simultaneously for both the target and the neighbor stimuli, each varying over 6 levels of contrast: 0%, 4%, 8%, 16%, 32%, and 64%. For most conditions, the relationship between the amplitude of target response and the contrast of the neighbor stimulus, as well as the amplitude of the response to the target stimulus, were described with ...