BACKGROUND Although it is well established that methylphenidate (MPH) enhances sustained attention, the neural mechanisms underpinning this improvement remain unclear. We examined how MPH influenced known electrophysiological precursors of lapsing attention over different time scales. METHODS We measured the impact of MPH, compared with placebo, on behavioral and electrocortical markers while...

A visual evoked potential (VEP) component that appears in the power spectrum only during binocular fusion has recently been discovered. When both eyes are stimulated with the same checkerboard but at different pattern reversal rates, this fusional component appears at a frequency intermediate between the two stimulus frequencies. We have proposed a model to explain the appearance of this interm...

We have investigated whether ageing affects selectively the responses to equiluminant patterns of pure colour contrast. In two groups of subjects (mean ages 29 and 72 yr) contrast thresholds were measured psychophysically for the detection and for the discrimination of the direction of motion of drifting gratings. The gratings were modulated either in pure luminance contrast (and uniform colour...

The effect of contrast on visual evoked potential (VEP) amplitude was examined in nine observers. A 6.0 cycles/deg (cpd) grating was modulated in an "on-off" mode at 7.5 Hz. The VEP response contains significant first and second harmonic components: their growth with contrast is parallel, each function consisting of two limbs. The data are consistent with the hypothesis that the pattern VEP obt...

One week of solitary confinement of prison inmates produced significant changes in their EEG frequency and visual evoked potentials (VEP) that parallel those reported in laboratory studies of sensory deprivation. EEG frequency declined in a nonlinear manner over the period. VEP latency, which decreased with continued solitary confinement, was shorter for these 5s than for control 5s whose VEP l...

background: we compared the wave amplitude of visually evoked potential (vep) between patients with esotropic and anisometropic amblyopic eyes and a normal group. methods: the wave amplitude of vep was documented in 2 groups of persons with amblyopia (15 with esotropia and 28 with anisometropia) and 1 group of individuals with normal visual acuity (n, 15). the amplitude of p100 was recorded mon...

The visual evoked potential (VEP) in the mouse is characterized and compared to responses obtained with the electroretinogram (ERG). The results indicate that: 1, the VEP originates in the visual cortex; 2, the rod and cone pathways contribute separately to the VEP; 3, temporal tuning functions for rod and cone ERGs are low pass and band pass, respectively; VEP tuning functions are both band pa...

Young infants actively gather information about their world through visual foraging, but the dynamics of this important behavior is poorly understood, partly because developmental scientists have often equated its essential components, looking and attending. Here we describe a method for simultaneously tracking spatial attention to fixated and nonfixated locations during free looking in 12-week...

Temporal analysis of the multifocal cortical visual evoked potential (VEP) was studied using pseudo-random (m-sequence) achromatic stimulation. The effects of variation of luminance contrast on the first-order response were complex. At low to mid contrasts (< 60%), a wave doublet (P100-N115) predominated. A second wave complex (N100-P120-N160) dominated at high contrasts. The second-order respo...

Results from psychophysics and single-unit recordings suggest that color vision comprises multiple stages of processing. Postreceptoral channels appear to consist of both a stage of broadly tuned opponent channels that compare cone signals and a subsequent stage, which includes cells tuned to many different directions in color space. The chromatic visual evoked potential (crVEP) has demonstrate...