Both monocular and binocular signals contribute to motion rivalry

Evidence for strictly monocular processing in visual motion opponency and Glass pattern perception

When presented with locally paired dots moving in opposite directions, motion selective neurons in the middle temporal cortex (MT) reduce firing while neurons in V1 are unaffected. This physiological effect is known as motion opponency. The current study used psychophysics to investigate the neural circuit underlying motion opponency. We asked whether opposing motion signals could arrive from different eyes into the receptive field of a binocular neuron while still maintaining motion opponency. We took advantage of prior findings that orientation discrimination of the motion axis (along which paired dots oscillate) is harder when dots move counter-phase than in-phase, an effect associated with motion opponency. We found that such an effect disappeared when paired dots originated from different eyes. This suggests that motion opponency, at some point, involves strictly monocular processing. This does not mean that motion opponency is entirely monocular. Further, we found that the effect of a Glass pattern disappeared under similar viewing conditions, suggesting that Glass pattern perception also involves some strictly monocular processing.

Motion processing, directional selectivity, and conscious visual perception in the human brain

Several human and monkey studies have demonstrated a close relationship between motion perception and activation of area V5, leading to the general view that activity in this area correlates with the subjective experience of motion. In the present study, we investigate whether the responses of this area are still governed by the motion percept when the latter is in conflict with the reality of the physical visual stimulation. We simultaneously presented two different, specially designed random-dot kinematograms, one to each eye. These stimuli either both had a single direction of motion and worked in synergy, or had opposite motion directions and thus cancelled each other out perceptually. In this way, we were able to pit the visual stimulus (one vs. two stimulating directions) against the reported perception (directional motion vs. motion noise) of human volunteers during fMRI experiments. We found that a strong motion stimulus that is weakly perceived is more effective in activating V5 (as well as V3) than a weaker motion stimulus, which is nevertheless robustly perceived. Thus, contrary to the prevailing view of perception being the correlate of activity in higher visual areas, we show here that activity is instead dominated by the properties of the physical stimulus, raising the question of whether there is a subpopulation of cells in V5 whose activity is critical for generating the motion percept. In addition, our results provide the first robust evidence for the presence of directionally selective neuronal populations in human prestriate cortex.

Perceptual issues in the use of head-mounted visual displays

OBJECTIVE

We provide a review and analysis of much of the published literature on visual perception issues that impact the design and use of head-mounted displays (HMDs).

BACKGROUND

Unlike the previous literature on HMDs, this review draws heavily from the basic vision literature in order to help provide insight for future design solutions for HMDs.

METHOD

Included in this review are articles and books found cited in other works as well as articles and books obtained from an Internet search.

RESULTS

Issues discussed include the effect of brightness and contrast on depth of field, dark focus, dark vergence, and perceptual constancy; the effect of accommodation-vergence synergy on perceptual constancy, eyestrain, and discomfort; the relationship of field of view to the functioning of different visual pathways and the types of visual-motor tasks mediated by them; the relationship of binocular input to visual suppression; and the importance of head movements, head tracking, and display update lag.

CONCLUSION

This paper offers a set of recommendations for the design and use of HMDs.

APPLICATION

Consideration of the basic vision literature will provide insight for future design solutions for HMDs.