We have examined the correlations between direct surface-finish metrology techniques and normalincidence, soft x-ray reflectance measurements of highly polished x-ray multilayer mirrors. We find that, to maintain high reflectance, the rms surface roughness of these mirrors must be less than ~ 1 Å over the range of spatial frequencies extending approximately from 1 to 100 µm(-1)1 (i.e., spatial ...

Neuronal spatial frequency tuning in primary visual cortex (V1) substantially changes over time. In both primates and cats, a shift of the neuron's preferred spatial frequency has been observed from low frequencies early in the response to higher frequencies later in the response. In most cases, this shift is accompanied by a decreased tuning bandwidth. Recently, the mouse has gained attention ...

Previous work (Verrillo, 1963, 1968) has shown that when measured as a change in absolute threshold, spatial summation occurs only at vibration frequencies above 40 Hz. The present study measured vibrotactile spatial summation at suprathreshold amplitudes. A matchingtask was used to investig-ate the effect of varying contactor size on sensory magnitude at three different vibration frequencies. ...

We measured contrast thresholds for the identification of faces and facial expressions as a function of the center spatial frequency of narrow-band additive noise. In adults, masking of mid spatial frequencies (11-16c/fw) caused the largest elevation in contrast threshold (Experiment 1). Ideal observer analysis revealed that adults were equally sensitive to available information at low and mid ...

Perceived contrast is reduced after prolonged exposure to a textured pattern (contrast adaptation). The size of this effect is dependent on the relationship between the adapting contrast and the test contrast. It is generally accepted that the greatest reductions occur when the adapting contrast is much higher than the test contrast. Here this relationship was examined for a wide range of spati...

Neurophysiological and behavioral reports converge to suggest that monocular neurons in the primary visual cortex are biased toward low spatial frequencies, while binocular neurons favor high spatial frequencies. Here we tested this hypothesis with functional magnetic resonance imaging (fMRI). Human participants viewed flickering gratings at one of two spatial frequencies presented to either th...

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...