Relative latency of visual evoked responses to reversals in contrast, orientation, and motion direction

Contrast response of human visual mechanismsensitive to orientation and direction of motion.

-A slowly moving grating of low spatial frequency differentially raises the thresholdof various kinds of test targets. Systematic variation of the contrast of the adaptation gratingseparates two distinct components of this response. One component depends upon thegrating's orientation and is a power function of contrast. This component is independentof the grating's movement. The...

Attention modulates responses to motion reversals in human visual cortex.

Selective attention modulates brain responses in visual cortex. A common finding, using functional magnetic resonance imaging or event-related potentials, is that responses to attended relative to unattended stimuli are potentiated. We report an exceptional circumstance in a motion-processing paradigm. Participants viewed superimposed stationary and moving dots and were instructed to attend to ...

The relative importance of contrast and motion in visual detection.

Neural correlates of spontaneous direction reversals in ambiguous apparent visual motion.

Looking at bistable visual stimuli, the observer experiences striking transitions between two competing percepts while the physical stimulus remains the same. Using functional imaging techniques, it is therefore possible to isolate neural correlates of perceptual changes that are independent of the low-level aspects of the stimulus. Previous experiments have demonstrated distributed activations...

Orientation selectivity of motion-boundary responses in human visual cortex.

Motion boundaries (local changes in visual motion direction) arise naturally when objects move relative to an observer. In human visual cortex, neuroimaging studies have identified a region (the kinetic occipital area [KO]) that responds more strongly to motion-boundary stimuli than to transparent-motion stimuli. However, some functional magnetic resonance imaging (fMRI) studies suggest that KO...