No Dissociation between Perception and Action in Patient DF When Haptic Feedback is Withdrawn

Abstract

Goodale et al. (1991) reported a striking dissociation between vision for perception and action. They examined DF, a human patient who had damage to her ventral visual stream and suffered from visual form agnosia. She was unable to perceive an object's size but could match the opening of her hand to the object's size during grasping. It was concluded that grasping relied on a separate representation of visual size in the dorsal stream and required no visual input from the ventral stream. This observation inspired the influential perception-action model, which claimed separate visual streams for perception and action. However, in grasping (but not in corresponding perceptual tasks), participants receive haptic feedback after each trial. Using this feedback, DF might compensate for her impaired size-vision. I reexamined DF's grasping behavior using a mirror apparatus to dissociate the image of an object from its physical presence. DF's grasping was only normal when she received haptic feedback. Thus, in grasping, DF can rely on haptic feedback to compensate for her deficit in size-perception. This can explain why her grasping is significantly better than her perceptual performance. The findings emphasize the extent of early interstream interactions and highlight the multimodal nature of sensory processing in the dorsal stream.

Effect of visual and haptic feedback on grasping movements

“…However, even when haptic feedback was available throughout the block, the MGA was subject to the same depth constancy failure observed during Pretraining and Posttraining blocks. This second compelling result concerning the similarity between perceptual biases and biases observed for reach-to-grasp actions endorses the hypothesis that processing of visual information for both perceptual judgments and visually guided actions is indicative of similar and interrelated underlying mechanisms (Foster et al 2011;Franz et al 2000Franz et al , 2009Franz and Gegenfurtner 2008;Schenk 2010Schenk , 2012. In particular, the present findings would indicate that depth scaling of binocular disparities is the same for perception and action, a result incompatible with the dual visual systems theory (Goodale et al 1991;Goodale and Milner 1992).…”

“…In the latter cases, the action is shown to be subject to the different biases similar to those found in perceptual tasks, leading to the assumption that different perceptual processes are engaged depending on the different feedback available (Goodale et al 1994;Whitwell et al 2014). Then again, what these studies show is an undeniable inaccuracy in object depth and distance estimates in the absence of haptic feedback, supporting the key role the haptic feedback has in grasping actions Schenk 2012;Whitwell et al 2014). Nevertheless, the present findings demonstrate that also in the presence of all sensory feedback, haptic and visual, depth constancy is still compromised.…”

“…Haptic feedback, which takes place at the end of the movement, provides additional information about intrinsic properties of the object, such as shape and size. It can be assumed that this feedback corrects the initially biased visual estimate of the object size to allow accurate future grasping movements 2010, 2012.…”

“…Virtual reality setups permit the selective presentation of feedbacks, both visual and haptic, allowing systematic investigation of their effect on reach-to-grasp actions (Bingham et al 2000Bradshaw and Elliott 2003;Hibbard and Bradshaw 2003;Melmoth et al 2007;Schenk 2012;Servos 2000;Servos et al 1992;Smeets et al 2006). In this respect, some studies have tested grasping and reaching movements by asking subjects to perform the action beside the object, rather than performing it as an object-oriented action (Goodale et al 1994), or by limiting the availability of visual information to the phase preceding the movement execution, letting subjects perform the movement based only on the memory of the object (Goodale et al 1994).…”

Perceiving and acting upon weight illusions in the absence of somatosensory information

“…Our sense of touch, for example, is critical for a range of behaviors, from simple manual localization (Rao and Gordon 2001) to complex object interaction. Indeed, recent work has even suggested that haptic feedback might underpin the apparent skill with which the famous visual form agnosic patient DF grasps objects that she cannot visually distinguish (Schenk 2012; see Whitwell and Buckingham 2013 for discussion). It is clear that the role of haptic feedback in sensorimotor control is complex and relatively understudied.…”