Perception and Action in ‘Visual Form Agnosia’

Milner, A. David; Perrett, David I.; Johnston, Robert Mackenzie; Benson, Philip J.; Jordan, Timothy R.; Heeley, D.W.; Bettucci, D.; Mortara, F.; Mutani, Roberto; Terazzi, Emanuela; Davidson, D. L. W.

doi:10.1093/brain/114.1.405

Cited by 551 publications

(213 citation statements)

References 26 publications

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“…D.F. failed in visual perceptual tasks while her visuomotor performance was not impaired (Milner et al, 1991). A recent study (Schenk, 2006) revealed that the discrepancy in her behavior was not due to different response modes, but rather due to deficits in different spatial representations (Himmelbach et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Spatial task context makes short-latency reaches prone to induced Roelofs illusion

Taghizadeh

Gail

2014

Front. Hum. Neurosci.

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The perceptual localization of an object is often more prone to illusions than an immediate visuomotor action towards that object. The induced Roelofs effect (IRE) probes the illusory influence of task-irrelevant visual contextual stimuli on the processing of task-relevant visuospatial instructions during movement preparation. In the IRE, the position of a task-irrelevant visual object induces a shift in the localization of a visual target when subjects indicate the position of the target by verbal response, key-presses or delayed pointing to the target (“perception” tasks), but not when immediately pointing or reaching towards it without instructed delay (“action” tasks). This discrepancy was taken as evidence for the dual-visual-stream or perception-action hypothesis, but was later explained by a phasic distortion of the egocentric spatial reference frame which is centered on subjective straight-ahead (SSA) and used for reach planning. Both explanations critically depend on delayed movements to explain the IRE for action tasks. Here we ask: first, if the IRE can be observed for short-latency reaches; second, if the IRE in fact depends on a distorted egocentric frame of reference. Human subjects were tested in new versions of the IRE task in which the reach goal had to be localized with respect to another object, i.e., in an allocentric reference frame. First, we found an IRE even for immediate reaches in our allocentric task, but not for an otherwise similar egocentric control task. Second, the IRE depended on the position of the task-irrelevant frame relative to the reference object, not relative to SSA. We conclude that the IRE for reaching does not mandatorily depend on prolonged response delays, nor does it depend on motor planning in an egocentric reference frame. Instead, allocentric encoding of a movement goal is sufficient to make immediate reaches susceptible to IRE, underlining the context dependence of visuomotor illusions.

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Section: Discussionmentioning

confidence: 99%

Spatial task context makes short-latency reaches prone to induced Roelofs illusion

Taghizadeh

Gail

2014

Front. Hum. Neurosci.

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“…For example, whereas visual illusions may affect our perception of an object's size or position, it has been reported that visually guided reaching can be relatively immune from such perceived distortions (38,39). Similarly, patients with brain damage may be able to act appropriately on objects despite dramatic perceptual disruption that would seem to preclude such accurate actions (40). Furthermore, neurons in some sensorimotor areas are activated by visual stimuli more quickly than neurons in many areas of visual cortex (41), indicating that sensorimotor mechanisms can be initiated without relying on a hierarchy of visual processing to feed them perceptual information.…”

Section: Discussionmentioning

confidence: 99%

Attentional modulation of sensorimotor processes in the absence of perceptual awareness

Sumner

Tsai

et al. 2006

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

114

108

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Attention modulates visual perception and is generally considered inextricably linked with conscious awareness: we become aware of stimuli as we attend to them, and we attend to stimuli as we become aware of them. Recent evidence suggests that attention can also modulate the effects of stimuli that remain invisible, and a natural explanation is that attention enhances weak perceptual representations, bringing them closer to conscious threshold even if they do not reach that threshold. However, there is also the possibility that attention may modulate neural processes that are entirely separate from those supporting conscious perception: sensorimotor mechanisms that do not create awareness however much they are enhanced. Here we provide evidence in support of this second hypothesis by showing that attentional cueing can modulate the behavioral response to invisible stimuli in a way that is distinct from enhancing their visibility. We used a masked-prime paradigm that produces a negative or positive compatibility effect depending on the perceptual strength (duration or brightness) of the prime. We found that attention enhanced the effect of both visible and invisible primes and also increased the likelihood of detecting the prime (i.e., boosted perceptual strength). Crucially, the pattern of attentional influence on priming could not be explained by attentional modulation of the prime's perceptual strength but was predicted by a direct attentional influence on the nonconscious priming process itself. Therefore, in addition to regulating what we perceive, attention seems to influence our behavior through sensorimotor processes that are not involved in conscious awareness.priming ͉ unconscious ͉ motor inhibition ͉ action

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“…'s brain that provided the important clue as to how these different mechanisms might be realized in neural circuitry. An early structural MRI [16] showed evidence of extensive bilateral damage in the ventral visual stream. More recent high-resolution MRI scans [17,18] have confirmed this ventral-stream damage but revealed that the lesions are focused in the lateral occipital cortex (area LO), an area that we now know is involved in the visual recognition of objects, particularly their geometric structure [19].…”

Section: Neuropsychological Dissociations Between Perception and Actionmentioning

confidence: 99%

How (and why) the visual control of action differs from visual perception

Goodale

2014

Proc. R. Soc. B.

128

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Vision not only provides us with detailed knowledge of the world beyond our bodies, but it also guides our actions with respect to objects and events in that world. The computations required for vision-for-perception are quite different from those required for vision-for-action. The former uses relational metrics and scene-based frames of reference while the latter uses absolute metrics and effector-based frames of reference. These competing demands on vision have shaped the organization of the visual pathways in the primate brain, particularly within the visual areas of the cerebral cortex. The ventral 'perceptual' stream, projecting from early visual areas to inferior temporal cortex, helps to construct the rich and detailed visual representations of the world that allow us to identify objects and events, attach meaning and significance to them and establish their causal relations. By contrast, the dorsal 'action' stream, projecting from early visual areas to the posterior parietal cortex, plays a critical role in the real-time control of action, transforming information about the location and disposition of goal objects into the coordinate frames of the effectors being used to perform the action. The idea of two visual systems in a single brain might seem initially counterintuitive. Our visual experience of the world is so compelling that it is hard to believe that some other quite independent visual signal-one that we are unaware of-is guiding our movements. But evidence from a broad range of studies from neuropsychology to neuroimaging has shown that the visual signals that give us our experience of objects and events in the world are not the same ones that control our actions.

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Perception and Action in ‘Visual Form Agnosia’

Cited by 551 publications

References 26 publications

Spatial task context makes short-latency reaches prone to induced Roelofs illusion

Spatial task context makes short-latency reaches prone to induced Roelofs illusion

Attentional modulation of sensorimotor processes in the absence of perceptual awareness

How (and why) the visual control of action differs from visual perception

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