Grasping in the real world: choosing goals and avoiding obstacles
The visual control of grasping and the neural circuits supporting this behaviour have typically been studied by presenting people with a single goal object in an otherwise empty workspace. The real world of course is not nearly so accommodating. Workspaces such as the breakfast table and one’s desktop are normally cluttered with a number of objects, some of which might be goals for action on a particular occasion and some of which might be obstacles. Selecting and executing an action toward only one object in such complex environments present the visuomotor system with a significant challenge. Recent research has shown that, to overcome this problem, the brain sometimes encodes motor plans to multiple objects simultaneously, and these motor plans then compete for selection. The dorsal premotor and the posterior parietal cortex have been shown to play central roles in this coding. Work in our laboratory has shown that the decision to settle on a single motor plan is influenced both by incoming sensory information and previous experience. There also appears to be an upper limit of around 3 or 4 to the number of motor plans that can be encoded at the same time. Once people start to reach towards the selected goal object, they typically avoid other objects in the workspace, taking into account their position and size in a fairly ‘automatic’ manner. Kinematic studies of actions made by neurological patients in our laboratory and others suggest that the location of potential obstacles and the degree of interference they pose are encoded by the dorsal visual stream during action planning. Taken together, these findings suggest that action planning recruits circuitry in the parieto-premotor network, and that this activity may modulate the coding of objects in earlier visual areas.
Meet the speaker, reception with drinks and nibbles organized in L68, Department of Psychology.
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