Abstract
A long history of neuropsychological research has shown the visual control of grasping and other skilled movements depends on the integrity of visual projections to the dorsal visual stream in the posterior parietal cortex. Patients with lesions to the dorsal stream are unable to direct their hands towards or grasp visual targets in the contralesional visual field, despite being able to describe the size, orientation, and location of those targets. Other patients with lesions to the ventral stream are able to grasp objects accurately and efficiently despite being unable to report the very object features controlling their actions. More recent imaging studies of both neurological patients and healthy controls has confirmed the role of the dorsal stream in transforming visual information into the required coordinates for action. In this presentation, I will discuss research from our lab showing that visual information about the metrical properties of goal objects may reach the dorsal stream via pathways that bypass the geniculostriate pathway. I will go on to show that manual interactions with some classes of objects, such as tools, requires that visual information about those objects be processed by circuits in both the ventral and the dorsal stream. Finally, I will speculate that some of the other higher-order functions of the parietal lobe, such as its evident role in numerical processing and working memory, may have evolved from the need to plan actions to multiple goals.
Meeting abstract presented at VSS 2016