Reports of modulations of early visual processing suggest that retinotopic visual cortex may actively predict upcoming stimuli. We tested this idea by showing healthy human participants images of human faces at fixation, with different emotional expressions predicting stimuli in either the upper or the lower visual field. On infrequent test trials, emotional faces were followed by combined stim...

Localized evoked activity of the human cortex produces fast changes in optical properties that can be detected noninvasively (event-related optical signal, or EROS). In the present study a fast EROS response (latency approximately 100 ms) elicited in the occipital cortex by visual stimuli showed spatial congruence with fMRI signals and temporal correspondence with VEPs, thus combining subcentim...

An experiment was conducted on naive human subjects to measure the time benefits on finger reaction times produced by the offset of a central fixation point 200 ms before the appearance of a target stimulus in the periphery. Subjects produced a shift advancement of manual reaction times. Simultaneously, the event-related potentials were recorded. The gap paradigm induced offset visual evoked po...

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...