Dual Visual System Research Articles

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<p>Goal. A representation is a multisensory model of an object that may or may not be represented in direct perceptual experience. In this regard, the question arises about the possibility of including in the representation information about the way of action with an object (motor programs). The purpose of this work is to analyze the existing theoretical concepts and empirical studies of the thesis about the inclusion of motor knowledge in the representation of an object and the influence of this knowledge on other cognitive processes. Methods. The work examines such theoretical approaches as the theory of the dual visual system, the model of embedded representation, as well as approaches based on manipulation and intention. In particular, the effect of compatibility is analyzed, which consists in reaction time reduction in the case of a congruence of the executed motor program and the perceived object. Results. The compatibility effect can be found in naming, categorization, and visual search tasks. The conditions for the occurrence of the compatibility effect in visual search are considered. Conclusions. It is assumed that there are two alternative explanations for the compatibility effect in the visual search — the conflict resolution in working memory or the inhibition of affordances hypothesis.</p>

Conscious vision guides motor action—rarely

ABSTRACT According to Milner and Goodale’s dual visual systems (DVS) theory, a division obtains between visual consciousness and motor action, in that the visual system producing conscious vision (the ventral stream) is distinct from the one guiding action (the dorsal stream). That there would be this division is often taken (by Andy Clark and others) to undermine the folk view on how consciousness and action relate. However, even if this division obtains, this leaves open the possibility that conscious ventral information is often transmitted to the unconscious dorsal stream and then used to guide action, a possibility seeming to preserve a significant role for consciousness in action. This article assesses this possibility. In course of doing so, we will review those arguments recently having been made against the DVS view on how visual consciousness and action relate (ones due to, e.g., Briscoe and Schwenkler, or Schenk and McIntosh). What we will find is that, if we properly analyze the data upon which these arguments are based, we are still left with the impression that the DVS view is largely correct; i.e., it is only rarely that visual experience guides action.

Dislocation, Not Dissociation: The Neuroanatomical Argument Against Visual Experience Driving Motor Action

AbstractCommon sense suggests that visual consciousness is essential to skilled motor action, but Andy Clark—inspired by Milner and Goodale's dual visual systems theory—has appealed to a wide range of experimental dissociations to argue that such an assumption is false. Critics of Clark's argument (e.g. Wallhagen, Mole) contend that the content driving motor action is actually within subjects' experience, just not easily discovered. In this article, I argue that even if such content exists, it cannot be guiding motor action, since a review of current visual neuroscience indicates that the visual brain areas producing conscious representations are distinct from those driving motor action.

Perception-action dissociations depend on the luminance contrast of the stimuli

The observation that near-threshold low-contrast visual distractors can equally influence perceptual state and goal-directed motor responses was recently taken as an argument against a sharp separation between a conscious vision for perception and an unconscious vision for action. However, data supporting the dual visual system theory have principally involved high-contrast stimuli. In the present study, we assessed the effect of varying the contrast of a near-threshold visual distractor while keeping its visibility constant with backward noise masks. Eight participants performed fast manual reaching movements toward a highly visible target while subsequently reporting the presence/absence of a near-threshold distractor appearing at the opposite location with respect to the body midline. For all distractor contrasts, hand trajectory deviations toward the distractor were observed when the distractor was present and detected. When the distractor remained undetected deviations also occurred, but for higher contrasts. The subliminal motor effect traditionally observed in visual masking studies may therefore primarily depend on the luminance contrast of the interfering stimuli. These results suggest that dissociations between perceptual and motor responses can be explained by a single-signal model involving differential thresholds for perception and action that are specifically modulated as a function of both the requirements of the task and the contrast level of the stimuli. Such modulation is compatible with neurophysiological accounts of visual masking in which feedforward activation to--and feedback activation from--higher visual areas are correlated with the actual presence of the stimulation and its conscious perception, respectively.

Differential control of light–dark adaptation in the ocelli and compound eyes of Triatoma infestans

The adaptation to light of compound eyes in insects has been extensively documented and their adaptive role is well understood. Much less attention has been paid, however, to the control of ocelli sensitivity, a study which could help us to understand the functional role of these simple eyes. We analyzed the dynamic changes in the distribution of screening pigments which occur in the ocelli of the haematophagous bug, Triatoma infestans, when the insects are subjected either to light/dark cycles (LD), to constant darkness (DD) or constant light (LL). We then compared these changes with those occurring in the compound eyes of the same individuals and found that, while compound eyes are subject to the control of an endogenous circadian clock, the adaptation of the ocelli is entirely dependent on environmental illumination. In addition, we have observed that environmental temperature is not involved in the control of screening pigments in either ocelli or compound eyes as a direct stimulus, nor as a Zeitgeber. The existence of a differential control in the components of the dual visual system represents an adaptive advantage in the adjustment of visual sensitivity in insects exposed to quick changes in lighting conditions in their natural habitat. We discuss the implications of our findings with regards to the biology of triatomines and with respect to the general understanding the functional role of insect ocelli.

Dual visual systems and working memory for object and spatial properties

Dual visual systems and working memory for object and spatial properties

Perception, action, and experience: Unraveling the golden braid

Much of our human mental life looks to involve a seamless unfolding of perception, action and experience: a golden braid in which each element twines intimately with the rest. We see the very world we act in and we act in the world we see. But more than this, visual experience presents us with the world in a way apt for the control and fine guidance of action. Or so it seems. Milner and Goodale's [Milner, D., Goodale, M. (1995). The visual brain in action. Oxford: Oxford University Press; Milner, A., Goodale, M. (2006). Epilogue: Twelve years on. In Milner, A., Goodale, M. (Ed.), The visual brain in action (2nd ed., pp. 207–252). Oxford: Oxford University Press] influential work on the dual visual systems hypothesis casts doubt on certain versions of this intuitive vision. It does so by prising apart the twining strands of conscious visual perception and the fine control of visuomotor action. Such a bold proposal is of major interest both to cognitive science and philosophy. In what follows I first clarify the major claims that the bold proposal involves, then examine three sets of worries and objections. The first set concern some important matters of detail. The second set concern a certain kind of conceptual or philosophical worry to the effect that the perception/action model unfairly equates visual experience itself with what are in fact certain elements within visual experience. The third set concern the very idea of conscious experience as a well-defined conceptual or experimental target. I conclude that the boldest versions of the Dual Visual Systems (2VS) story underestimate the variety and richness of visual experience, but that the general picture of visual uptake as a fragmented, multi-stream, multipurpose adaptation is correct, and still revealing after all these years.

What the hand can?t tell the eye: illusion of space constancy during accurate pointing

When we press an elevator button or pick up a coffee cup, different visual information is used to guide our reach and to form our conscious experience of these objects. But can the information guiding our hand be brought into awareness? The fact that we can see and feel our own hand in action suggests that it might be possible. However, the dual visual systems theory claims that on-line control of movement is governed by the dorsal stream of visual processing, which is largely unconscious. Two experiments are presented as strong tests of the hypothesis that the visual information guiding on-line pointing in healthy human adults is inaccessible for conscious report. Results show that participants are incapable of consciously accessing the information used in pointing, even though they can see and feel their hands in action and accurate performance depends on it.

Graspability and object processing in infants

This review pursues the idea that a dual visual system approach is fruitful for interpreting work on infant cognition. We provide examples from the visual perception and cognition literature demonstrating that the potential graspability of stimuli typically used in infant studies influence how these stimuli are processed by the infant brain. Specifically, we argue that small, local, familiar and moving stimuli are more likely to be processed by the dorsal (how or action) stream of visual processing. In contrast, larger, stationary objects are likely to be processed by the ventral (what or perception) stream. This analysis clarifies apparently conflicting results in the literature.

Target detection and localization in visual search: A dual systems perspective

The dual visual systems framework (Milner & Goodale, 1995) was used to explore target detection and localization in visual search. Observers searched for a small patch of tilted bars against a dense background of upright bars. Target detection was performed along with two different localization tasks: direct pointing, designed to engage the dorsal stream, and indirect pointing, designed to engage the ventral stream. The results indicated that (1) target detection was influenced more by orientation differences in 3-D space than by 2-D pictorial differences, (2) target localization was more accurate for direct than for indirect pointing, and (3) there were performance costs for indirect localization when it followed target detection, but not for direct localization. This is consistent with direct localization's having greater dependence on the dorsal visual system than either target detection or indirect localization.

The finger in flight: real-time motor control by visually masked color stimuli.

Current theories of dual visual systems suggest that color is processed in a ventral cortical stream that eventually gives rise to visual awareness but is only indirectly involved in visuomotor control mediated by the dorsal stream. If the dorsal stream is indeed less sensitive to color than the ventral stream, color stimuli blocked from awareness by visual masking should also be blocked from guiding fast motor responses. In this study, pointing movements to one of two isoluminant color targets were preceded by consistent or inconsistent color primes. Trajectories were strongly affected by priming, with kinematics implying a continuous flow of color information into executive brain areas while the finger was already moving. Motor effects were more sensitive to color of the primes than were deliberate attempts to identify the primes in forced-choice tasks based on visual awareness. Priming was observed even when masking was complete.

Visual Experience and Motor Action: Are the Bonds Too Tight?

How should we characterize the functional role of conscious visual experience? In particular, how do the conscious contents of visual experience guide, bear upon, or otherwise inform our ongoing motor activities? According to an intuitive and (I shall argue) philosophically influential conception, the links are often quite direct. The contents of conscious visual experience, according to this conception, are typically active in the control and guidance of our fine-tuned, real-time engagements with the surrounding three-dimensional world. But this idea (which I shall call the Assumption of Experience-Based Control) is hostage to empirical fortune. It is a hostage, moreover, whose safety is in serious doubt. Thus Milner and Goodale (1995) argue for a deep and abiding dissociation between the contents of conscious seeing, on the one hand, and the resources used for the online guidance of visuomotor action, on the other. This “dual visual systems” hypothesis, which finds many echoes in various other bodies of cognitive scientific research, poses a prima facie challenge to the Assumption of Experience-Based Control. More importantly, it provides (I shall argue) fuel for an alternative and philosophically suggestive account of the functional role of conscious visual experience.

The differential optomotor response of the four-eyed fish Anableps anableps.

The perception of motion is important for the survival and reproduction of many animals, including fish. In the laboratory, support for this idea comes from the observation that many fish show a tendency to follow a series of stripes revolving around a circular aquarium. This response, known as the optomotor response (OMR), is recognized as an innate behavior in many species. The 'four-eyed' fishes of the genus Anableps are an unusual fish from Central and South America and actually have only two eyes. Each eye is divided into upper and lower halves internally and externally. This peculiar dual visual system allows Anableps to feed on creatures that swim or land near or on the water surface or to flee from flying predators attacking from above. It was hypothesized that Anableps should also possess the OMR. We used the OMR as a test to investigate potential differential visual processing in Anableps on normal and 'blinded' fish (the eyes are actually covered--not physically blinded). It was found that the OMR does exist in Anableps and that the strength of this response is dependent on the visual field being tested--a stronger OMR was seen as a result of visual stimulation from the aerial environment.

Some factors affecting the rate of dark adaptation in certain insects

Mutant fruit-flies ( Drosophila melanogaster), which are rendered blind by intense light, gradually recover visual sensitivity to a test flash during dark adaptation—80 per cent recovery being achieved in some 30 to 60 sec. Changes in the time course of recovery and a refractory period, which may be considerable, occur with increasing duration or intensity of adaptation in a similar manner to that described for the chalky eyed mutant Calliphora which differs from the normal red eyed form only in the lack of screening eye-colour pigments. The mutant Drosophila has normal red eye colouration and is not simply excessively bleached by light as the Calliphora mutant. Wildtype Drosophila recover rapidly and abruptly in a similar manner to the hive-bee, 80 per cent recovery being achieved in 10 to 20 seconds or often less. It is suggested that processes limiting the rate of dark adaptation are common to the insects cited and the differences between the mutant and wildtype data indicate that the mutants lack certain parts of a common system. The present data add support to the theory of a dual visual system in the compound eye of Drosophila and suggest the mutant form described lacks a photopic mechanism.