Express saccades and superior colliculus responses are sensitive to short-wavelength cone contrast.

A key structure for directing saccadic eye movements is the superior colliculus (SC). The visual pathways that project to the SC have been reported to carry only luminance information and not color information. Short-wavelength-sensitive cones (S-cones) in the retina make little or no contribution to luminance signals, leading to the conclusion that S-cone stimuli should be invisible to SC neurons.

Shape selectivity and remapping in dorsal stream visual area LIP.

We explore the visual world by making rapid eye movements (saccades) to focus on objects and locations of interest. Despite abrupt retinal image shifts, we see the world as stable. Remapping contributes to visual stability by updating the internal image with every saccade.

Remapping for visual stability.

Visual perception is based on both incoming sensory signals and information about ongoing actions. Recordings from single neurons have shown that corollary discharge signals can influence visual representations in parietal, frontal and extrastriate visual cortex, as well as the superior colliculus (SC). In each of these areas, visual representations are remapped in conjunction with eye movements.

Representation of the ipsilateral visual field by neurons in the macaque lateral intraparietal cortex depends on the forebrain commissures.

Our eyes are constantly moving, allowing us to attend to different visual objects in the environment. With each eye movement, a given object activates an entirely new set of visual neurons, yet we perceive a stable scene. One neural mechanism that may contribute to visual stability is remapping.

Spatial updating in monkey superior colliculus in the absence of the forebrain commissures: dissociation between superficial and intermediate layers.

In previous studies, we demonstrated that the forebrain commissures are the primary pathway for remapping from one hemifield to the other. Nonetheless, remapping in lateral intraparietal cortex (LIP) across hemifield is still present in split brain monkeys. This finding indicates that a subcortical structure must contribute to remapping.

Trans-saccadic perception.

A basic question in cognition is how visual information obtained in separate glances can produce a stable, continuous percept. Previous explanations have included theories such as integration in a trans-saccadic buffer or storage in visual memory, or even that perception begins anew with each fixation. Converging evidence from primate neurophysiology, human psychophysics and neuroimaging indicate an additional explanation: the intention to make a saccadic eye movement leads to a fundamental alteration in visual processing itself before and after the saccadic eye movement.

Dynamic circuitry for updating spatial representations. III. From neurons to behavior.

Each time the eyes move, the visual system must adjust internal representations to account for the accompanying shift in the retinal image. In the lateral intraparietal cortex (LIP), neurons update the spatial representations of salient stimuli when the eyes move. In previous experiments, we found that split-brain monkeys were impaired on double-step saccade sequences that required updating across visual hemifields, as compared to within hemifield.

Remapping in human visual cortex.

With each eye movement, stationary objects in the world change position on the retina, yet we perceive the world as stable. Spatial updating, or remapping, is one neural mechanism by which the brain compensates for shifts in the retinal image caused by voluntary eye movements. Remapping of a visual representation is believed to arise from a widespread neural circuit including parietal and frontal cortex.

Spatial updating in area LIP is independent of saccade direction.

We explore the world around us by making rapid eye movements to objects of interest. Remarkably, these eye movements go unnoticed, and we perceive the world as stable. Spatial updating is one of the neural mechanisms that contributes to this perception of spatial constancy.

Corollary discharge and spatial updating: when the brain is split, is space still unified?

How does the brain keep track of salient locations in the visual world when the eyes move? In parietal, frontal and extrastriate cortex, and in the superior colliculus, neurons update or 'remap' stimulus representations in conjunction with eye movements. This updating reflects a transfer of visual information, from neurons that encode a salient location before the saccade, to neurons that encode the location after the saccade. Copies of the oculomotor command - corollary discharge signals - must initiate this transfer.

Active vision in parietal and extrastriate cortex.

Vision is an active process. We do not see the world directly; rather, we construct a representation of it from sensory inputs in combination with internal, nonvisual signals. In the case of spatial perception, our representation of the visual scene must take into account our own movements.

Dynamic circuitry for updating spatial representations. I. Behavioral evidence for interhemispheric transfer in the split-brain macaque.

Internal representations of the sensory world must be constantly adjusted to take movements into account. In the visual system, spatial updating provides a mechanism for maintaining a coherent map of salient locations as the eyes move. Little is known, however, about the pathways that produce updated spatial representations.

Dynamic circuitry for updating spatial representations. II. Physiological evidence for interhemispheric transfer in area LIP of the split-brain macaque.

With each eye movement, a new image impinges on the retina, yet we do not notice any shift in visual perception. This perceptual stability indicates that the brain must be able to update visual representations to take our eye movements into account. Neurons in the lateral intraparietal area (LIP) update visual representations when the eyes move.

Spatial updating in human parietal cortex.

Single neurons in monkey parietal cortex update visual information in conjunction with eye movements. This remapping of stimulus representations is thought to contribute to spatial constancy. We hypothesized that a similar process occurs in human parietal cortex and that we could visualize it with functional MRI.

Spatial working memory in human extrastriate cortex.

The performance of spatial working memory tasks is known to evoke activity in a set of higher-order association areas, including the prefrontal cortex, posterior parietal cortex and the frontal and supplementary eye fields. Recent physiological studies in monkey have shown that memory-related activity also is found in extrastriate cortex [J. Neurophysiol.

Updating of the visual representation in monkey striate and extrastriate cortex during saccades.

Neurons in the lateral intraparietal area, frontal eye field, and superior colliculus exhibit a pattern of activity known as remapping. When a salient visual stimulus is presented shortly before a saccade, the representation of that stimulus is updated, or remapped, at the time of the eye movement. This updating is presumably based on a corollary discharge of the eye movement command.