Delay abolishes the obstacle avoidance deficit in unilateral optic ataxia

Rice, Nichola J.; Edwards, Martin; Schindler, Igor; Punt, David; McIntosh, Robert D.; Humphreys, Glyn W.; Lestou, Vaia; Milner, A. David

doi:10.1016/j.neuropsychologia.2008.01.012

Cited by 47 publications

(38 citation statements)

References 24 publications

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“…To investigate obstacle avoidance in CB, we adapted a task used previously in healthy individuals and in neurological patients (1,4,5,7,8). In this task, CB was required to make reaches from a start button (depth 15 cm) to a target strip (5 cm wide at a depth of 55 cm) with his right hand as quickly and accurately as possible (i.e., in ''real-time''), while avoiding obstacles (depth 35 cm) that could either be located laterally either 10 cm from the midline (''in'') or 15 cm from midline (''out'') in his right (sighted) or left (blind) visual field or in both visual fields.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies examining obstacle avoidance in neurological patients have indicated that lesions to the dorsal stream severely disrupt the ability to avoid obstacles (4,5), whereas lesions to the ventral stream do not impair obstacle avoidance (6). That is, patients with damage to the dorsal stream who have no trouble recognizing objects nevertheless have difficulty taking into account the position of obstacles while reaching.…”

mentioning

confidence: 99%

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“Real-time” obstacle avoidance in the absence of primary visual cortex

Striemer

Chapman

Goodale

2009

Proc. Natl. Acad. Sci. U.S.A.

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When we reach toward objects, we easily avoid potential obstacles located in the workspace. Previous studies suggest that obstacle avoidance relies on mechanisms in the dorsal visual stream in the posterior parietal cortex. One fundamental question that remains unanswered is where the visual inputs to these dorsal-stream mechanisms are coming from. Here, we provide compelling evidence that these mechanisms can operate in ''real-time'' without direct input from primary visual cortex (V1). In our first experiment, we used a reaching task to demonstrate that an individual with a dense left visual field hemianopia after damage to V1 remained strikingly sensitive to the position of unseen static obstacles placed in his blind field. Importantly, in a second experiment, we showed that his sensitivity to the same obstacles in his blind field was abolished when a short 2-s delay (without vision) was introduced before reach onset. These findings have far-reaching implications, not only for our understanding of the time constraints under which different visual pathways operate, but also in relation to how these seemingly ''primitive'' subcortical visual pathways can control complex everyday behavior without recourse to conscious vision.blindsight ͉ dorsal stream ͉ visuomotor control ͉ visual pathways ͉ consciousness

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

“Real-time” obstacle avoidance in the absence of primary visual cortex

Striemer

Chapman

Goodale

2009

Proc. Natl. Acad. Sci. U.S.A.

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“…Milner, Paulignan, et al (1999) have argued that this improvement occurs because the patients now use a memory of the stimulus location, based on perceptual processing carried out at the time of stimulation by the relatively intact ventral stream. In fact the improvements with delay in patients with optic ataxia have further been demonstrated for grasping (Milner et al, 2001) and, very recently, for obstacle avoidance (Rice et al, 2008).…”

Section: Introductionmentioning

confidence: 91%

Immediate and delayed reaching in hemispatial neglect

et al. 2009

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“…The analysis revealed a significant main effect of Repetition for un-primed trials in the The analyses presented in Sections 3.2.3-3.2.6 demonstrate that repetition is a significant factor in both Allocentric and Egocentric conditions but for different aspects of the 17 Delay in spatial priming experiment and therefore presumably for different reasons. Repetition was a significant factor for Allocentric un-primed sequences but not for Allocentric primed sequences, while the reverse was true for the Egocentric condition.…”

Section: Allocentric Group: Un-primed Sequencesmentioning

confidence: 87%

“…To explain this difference in delayed and non-delayed action it is argued 3 Delay in spatial priming that when there is a delay between target presentation and initiating a motor response towards it, as egocentric representations are unable to survive the delay period, the motor system is forced to rely on less accurate allocentric representations about the target location, which are presumably stored in the ventral stream. Introducing a delay differentially affects the motor performance of patients with dorsal and ventral stream damage: delay leads to an improvement in the visuomotor performance of patients with optic ataxia [15]; [16] ; [17] and a decline in the visuomotor performance of patients with visual agnosia [18] ; [19]. It is argued that the delay forces the motor system to rely on information from the ventral stream, meaning that in the case of a damaged dorsal stream (i.e.…”

Section: Introductionmentioning

confidence: 99%

Comparing the effect of temporal delay on the availability of egocentric and allocentric information in visual search

Ball

Birch

Lane

et al. 2017

Behavioural Brain Research

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(2017) 'Comparing the e ect of temporal delay on the availability of egocentric and allocentric information in visual search. ', Behavioural brain research., Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractFrames of reference play a central role in perceiving an object's location and reaching to pick that object up. It is thought that the ventral stream, believed to subserve vision for perception, utilises allocentric coding, while the dorsal stream, argued to be responsible for vision for action, primarily uses an egocentric reference frame. We have previously shown that egocentric representations can survive a delay; however, it is possible that in comparison to allocentric information, egocentric information decays more rapidly. Here we directly compare the effect of delay on the availability of egocentric and allocentric representations.We used spatial priming in visual search and repeated the location of the target relative to either a landmark in the search array (allocentric condition) or the observer's body (egocentric condition). Three inter-trial intervals created minimum delays between two consecutive trials of 2, 4, or 8 seconds. In both conditions, search times to primed locations were faster than search times to un-primed locations. In the egocentric condition the effects were driven by a reduction in search times when egocentric information was repeated, an effect that was observed at all three delays. In the allocentric condition while search times did not change when the allocentric information was repeated, search times to un-primed target locations became slower. We conclude that egocentric representations are not as transient as previously thought but instead this information is still available, and can influence behaviour, after lengthy periods of delay. We also discuss the possible origins of the differences between allocentric and egocentric priming effects.

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Delay abolishes the obstacle avoidance deficit in unilateral optic ataxia

Cited by 47 publications

References 24 publications

“Real-time” obstacle avoidance in the absence of primary visual cortex

“Real-time” obstacle avoidance in the absence of primary visual cortex

Immediate and delayed reaching in hemispatial neglect

Comparing the effect of temporal delay on the availability of egocentric and allocentric information in visual search

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