A random-dot field undergoing counterphase flicker paradoxically appears to move in the same direction as head and eye movements, i.e. opposite to the optic-flow field. The effect is robust and occurs over a wide range of flicker rates and pixel sizes. The phenomenon can be explained by reversed phi motion caused by apparent pixel movement between successive retinal images. The reversed motion ...

Presenting the two eyes with incongruent stimuli leads to the phenomenon of interocular rivalry. At any given time, one of the stimuli is perceptually suppressed in order to avoid double vision. In squinting subjects, rivalry occurs permanently also for congruent stimuli because of developmental rearrangement of cortical circuitry. In this study, we have investigated the dynamics and stimulus d...

PURPOSE To investigate the effect of age on optokinetic nystagmus (OKN) in response to stimuli designed to preferentially stimulate the M-pathway. METHOD OKN was recorded in 10 younger (32.3 +/- 5.98 years) and 10 older (65.6 +/- 6.53) subjects with normal vision. Vertical gratings of 0.43 or 1.08 cpd drifting at 5 degrees /s or 20 degrees /s and presented at either 8% or 80% contrast were di...

Albino ferrets contrary to their pigmented conspecifics show no optokinetic nystagmus. Therefore, in this study motion perception was compared between pigmented and albino ferrets (Mustela putorius furo) trained to discriminate between coherently moving random dot patterns and dynamic noise stimuli in a two-alternative forced choice task. Fully coherently versus incoherently moving patterns cou...

Animal models suggest that the asymmetry of monocular optokinetic nystagmus (OKN) in young infants can be explained by a direct pathway from retina to the midbrain nucleus of the optic tract. However, earlier studies with hemispherectomized infants showed no evidence for OKN responses towards the damaged cortex that could be ascribed to this subcortical pathway. In longitudinal testing of two i...

BACKGROUND Optokinetic nystagmus (OKN) gain is asymmetrical between temporal to nasal (TN) and nasal to temporal (NT) stimulation in infancy and decreases at older ages. The age at which OKN gain becomes symmetrical and decreases is debated. The aim was to investigate OKN over the whole lifespan in a large sample of healthy subjects. METHODS In a prospective, cross sectional study OKN was tes...

To investigate whether up-down asymmetry similar to that reported in vertical optokinetic nystagmus (OKN), that is, larger OKN responses for upward motion than for downward motion, would appear in vertical vection, we conducted three experiments. In all three experiments, participants viewed a vertically moving random-dot pattern. In Experiments 1 and 2, participants reported vection using a jo...

While the chick is one of the widely used animal models for eye growth studies very little is known about its visual spatial resolution performance. Using optokinetic nystagmus responses as an indicator of stimulus visibility, we estimated the visual acuity of young chicks to be between 6.0 and 7.7 cycles deg-1 at 2 and 4 days of age and slightly higher, between 7.7 and 8.6 cycle deg-1, at 8 da...

Optokinetic nystagmus (OKN) is the sawtooth movement of the eye elicited when an observer views a repeated moving pattern. We present a method for identifying the presence and direction of OKN in recordings of the eye made using a standard off-the-shelf video-camera or webcam. Our approach uses vertical edge detection to determine the limbus/iris boundary, and we estimate the velocity of the ed...

Different types of fast eye movements, including saccades and fast phases of optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN), are coded by only partially overlapping neural networks. This is a likely cause for the differences that have been reported for the dynamic parameters of fast eye movements. The dependence of two of these parameters-peak velocity and duration-on saccadi...