An allocentric rather than perceptual deficit in patient D.F.

Abstract

The 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-prot 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.

No Dissociation between Perception and Action in Patient DF When Haptic Feedback is Withdrawn

“…In this model, the ventral system serves object and scene recognition and the dorsal system uses vision to guide actions (Milner and Goodale, 2006). But in recent years, many of the model's claims were challenged (Schenk and McIntosh, 2010;Schenk et al, 2011), most notably, its claim that action is immune to perceptual illusions (Smeets and Brenner, 2006;Franz and Gegenfurtner, 2008), its claim that the dorsal stream does not provide observer-invariant visual information (Konen and Kastner, 2008) and does not make a contribution to perception (Schenk, 2006), the assertion that visual form agnosia and optic ataxia constitute a proper double-dissociation (Pisella et al, 2006), and the assumption that memory-based action is not processed by the dorsal stream (Himmelbach and Karnath, 2005;Himmelbach et al, 2009). In response to this critique, Goodale and colleagues noticed that critics fail to take the evidence from their patient, DF, into account and argued that one cannot dispute the two-visual stream hypothesis unless an alternative account for DF's surprisingly good visuomotor behavior is provided (Milner and Goodale, 2008, Goodale and Milner, 2010, Westwood and Goodale, 2011.…”

Dissociations between vision for perception and vision for action depend on the relative availability of egocentric and allocentric information

“…Milner and Goodale (2008, p. 778) recently argued that "the fact that a task involves action does not mean that the performance of this task would engage vision for action." In their critique of a study of Schenk (2006), they argued that a manual matching task in which the participant is asked to move a finger to an arbitrary point is nothing else but a "manual report" of a perceptual estimate (Milner & Goodale, 2008).…”

Saccades reveal that allocentric coding of the moving object causes mislocalization in the flash-lag effect

“…Whereas it is undisputed that retinal extrapolation mechanisms compensate for neuronal processing delays of moving stimuli (Berry et al, 1999), the results of Experiment 2 indicate that this extrapolation mechanism might not be responsible for on differences in encoding strategies. As Schenk (2006) demonstrated, patient D.F., who suffers a bilateral damage to the ventral stream, is not unable to successfully complete perceptual judgment tasks (while motor-level responses are unimpaired), as was first proposed by Goodale and Milner (1992). Instead, patient D.F.…”

“…How- in visual illusions. According to the frame of reference explanation, differences between perceptual and motor responses obtained in previous studies are not due to dissociations between the corresponding systems, but rather to the type of encoding strategies used in the task (see, e.g., Bernardis, Knox, & Bruno, 2005;Bruno, 2001;Schenk, 2006). In particular, it has been proposed that visual illusions result from an allocentric encoding of stimuli, whereas immunity from visual illusions stems from an egocentric encoding strategy.…”