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[Visual suppression during eye movements (a brief review on the problem of the mechanisms and their role in visual perception). I. A brief review and the mechanisms].

A problem of visual suppression during eye movements is discussed. The short critical review of the main published papers is adduced. A comparative analysis of the literary and author's data has been considered. These data provide evidence for the existence of three but not two (how is maintained) mechanisms of visual suppression: a retinal, efferent copy, and proprioceptive (from extraocular muscles) signals. The proprioceptive mechanism is more powerful than efferent copy. Both retinal and extraretinal mechanisms of visual suppression are discussed in detail. The sources and the passage's pathways of the extraretinal signals are considered thoroughly. It is shown that the retino-geniculate system provide mainly retinal mechanisms vs the tecto-thalamic system provide extraretinal mechanisms.

Animals↗
PubMed1984

Single unit activity and visual perception of motion.

Extracellular recordings were carried out in the primary visual cortex of behaving macaque monkeys. Neurons were activated by moving a visual stimulus across their receptive fields during steady fixation and by moving their receptive fields (by visual tracking) at the same velocity across a stationary visual stimulus. Out of a total number of 123 cells studied, 111 were activated by the visual stimulation both during fixation and tracking. The remaining 12 cells showed good response during fixation and very weakened response during tracking. Our results show that a small percentage of striate neurons in macaque monkey could discriminate between the real motion of an object in the visual world and the self-induced displacement of its retinal image.

Animals↗
PubMed1997

Visual perception of egocentric distance as assessed by triangulation.

Two triangulation methods for measuring perceived egocentric distance were examined. In the triangulation-by-pointing procedure, the observer views a target at some distance and, with eyes closed, attempts to point continuously at the target while traversing a path that passes by it. In the triangulation-by-walking procedure, the observer views a target and, with eyes closed, traverses a path that is oblique to the target; on command from the experimenter, the observer turns and walks toward the target. Two experiments using pointing and 3 using walking showed that perceived distance, averaged over observers, was accurate out to 15 m under full-cue conditions. For target distances between 15 and 25 m, the evidence indicates slight perceptual underestimation. Results also show that observers, on average, were accurate in imaginally updating the locations of previously viewed targets.

Adolescent↗
PubMed1976

The visual perception of accelerated motion.

The present research is an investigation of how changes in the rate of motion are percieved. Five separate experiments were performed with the use of filmed stimulus material and a variety of response measures, including both categorical judgments and reporduction techniques. It was found that (a) the smaller the ratio of terminal to initial velocity, the less frequent the judgments of acceleration or deceleration, (b) deceleration was significantly easier to perceive than acceleration, (c) the perception of acceleration was facilitated when the velocity of a lead-in segment was the same as the velocity at onset of motion, (d) a short tunnel centered in the motion path facilitated the perception of acceleration and deceleration, and (e) instantaneous changes in velocity were much more easily perceived than gradual changes. A one-event model for the perception of motion change in which there is a continuous interplay between earlier, later, and interpolated motion segments is favored over a two-event model in which earlier and later segments of velocity are compared.

Acceleration↗
PubMed1997

Temporal hierarchy of the visual perceptive systems in the Mondrian world.

Our earlier psychophysical work has shown that colour and motion are not perceived at the same time, with colour leading motion by about 50-100 ms. In pursuing this work, we thought it would be interesting to use a more complex colour stimulus, one in which the wavelength composition of the light reflected or emitted from surfaces changes continually, without entailing a change in the perceived colour (colour constancy). We therefore used a Mondrian figure--an abstract multi-coloured scene with no recognizable objects--against which squares (either red or green) moved up and down, changing colour from red to green in various phase differences with the change in direction of motion. The red and green squares changed continually in their spectral characteristics, as did every other patch on the Mondrian. The results showed that colour is still perceived before motion, by about 80 ms.

Adult↗