Spontaneous in-flight accommodation of hand orientation to unseen grasp targets: A case of action blindsight

ABSTRACT

The division of labour between the dorsal and ventral visual pathways is well established. The ventral stream supports object identification, while the dorsal stream supports online processing of visual information in the service of visually guided actions. Here, we report a case of an individual with a right inferior quadrantanopia who exhibited accurate spontaneous rotation of his wrist when grasping a target object in his blind visual field. His accurate wrist orientation was observed despite the fact that he exhibited no sensitivity to the orientation of the handle in a perceptual matching task. These findings indicate that non-geniculostriate visual pathways process basic volumetric information relevant to grasping, and reinforce the observation that phenomenal awareness is not necessary for an object’s volumetric properties to influence visuomotor performance.

KEYWORDS:

• Blindsight
• dorsal stream
• grasping
• visuomotor
• visual object recognition
• parietal cortex
• cortical blindness
• PCA stroke

Acknowledgments

We are grateful to A.I. for his enthusiastic participation in these studies, to Duje Tadin for his assistance with the development of the letter detection and identification test and to the Seneca Nation of Indians, on whose traditional territory the University of Rochester resides.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the National Institutes of Health (NIH) [grant number R01NSO89069 to B.Z.M.]; a core grant to the Center for Visual Science [grant number P30 EY001319]; a grant from the Schmitt Program on Integrative Neuroscience (University of Rochester) to B.S. and B.Z.M; and an unrestricted grant from Research to Prevent Blindness to the Department of Ophthalmology at the University of Rochester.