We compared observers' ability to discriminate the direction of apparent motion using images which varied in their spatial characteristic; white or flat spectrum noise, and 1/f noise which has an amplitude spectrum characteristic of natural scenes. The upper spatial limit for discrimination (dmax) was measured using a two-flash random dot kinematogram (RDK), which consisted either of a pair of ...

We have constructed "limited lifetime" stochastic motion stimuli using Gabor functions instead of dots, thereby controlling the local attributes of spatial frequency and orientation. Human psychophysical data for direction discrimination using these stimuli reveal two qualitatively distinct kinds of processing. For small displacements, direction discrimination performance as a function of displ...

In 2 earlier sets of experiments, the author reported that shape discrimination in an otherwise empty visual field is facilitated when the target shape is preceded by a valid spatial precue (J. M. Henderson, 1991; J. M. Henderson & A. D. Macquistan, 1993). L. Shiu and H. Pashler (1994) recently suggested that these earlier results were due to the presence of multiple posttarget pattern masks. T...

Birds have excellent spatial acuity and colour vision compared to other vertebrates while spatial contrast sensitivity is relatively poor for unknown reasons. Contrast sensitivity describes the detection of gratings of varying spatial frequency. It is unclear whether bird brightness discrimination between large uniform fields is poor as well. Here we show that budgerigars (Melopsittacus undulat...

Current models of attention, typically claim that vision and audition are limited by a common attentional resource which means that visual performance should be adversely affected by a concurrent auditory task and vice versa. Here, we test this implication by measuring auditory (pitch) and visual (contrast) thresholds in conjunction with cross-modal secondary tasks and find that no such interfe...

Unilateral damage to the lateral occipital region in humans can give rise to impaired motion perception in the contralateral visual field [Plant et al. (1993), Brain, 116, 1303-1335]. We report the following characteristics of the residual vision. (i) Spatial acuity and spatial frequency discrimination are not affected. (ii) Contrast thresholds for direction-of-motion (DOM) discrimination of lu...

The limbic thalamus, specifically the anterior thalamic nuclei (ATN), contains brain signals including that of head direction cells, which fire as a function of an animal's directional orientation in an environment. Recent work has suggested that this directional orientation information stemming from the ATN contributes to the generation of hippocampal and parahippocampal spatial representation...

We studied perception in three patients with prosopagnosia of childhood onset. All had trouble with other 'within-category' judgments. All were deficient on face matching tests and severely impaired on tests of perception of the spatial relations of facial features and abstract designs, indicating a deficit in the encoding of coordinate relationships, similar to adult-onset prosopagnosia with l...

We used functional magnetic resonance imaging (fMRI) to investigate the neural circuitry underlying tactile spatial acuity at the human finger pad. Stimuli were linear, three-dot arrays, applied to the immobilized right index finger pad using a computer-controlled, MRI-compatible, pneumatic stimulator. Activity specific for spatial processing was isolated by contrasting discrimination of left-r...