Complex Action Analysis Labs

Spatial and Non-spatial Factors in Selection for Action

Laurel J. Buxbaum, PsyD, Principal Investigator

This five-year grant from the National Institutes of Health (NIH) focuses on how objects in the environment are identified and selected for the purpose of action, and whether objects may be associated with particular actions.

Several factors appear to be important in determining how rapidly we can select an object for action; that is, locate and identify a target object, filter out irrelevant objects, and grasp the target.

One factor is the location of the target and other objects. Items closest to the hand of the person are easiest to identify and select for action.

One of our studies explores whether the degree to which the objects are compatible with the intended action is another factor influencing the ease of target selection.

For example, when one intends to reach toward and grasp the handle of a cup, it may be that other handled objects in the environment compete strongly for our attention, and cause slowing in the target selection process. If one intends to push an object away with the palm of the hand, it may be that other handled objects in the environment do not compete very strongly for our attention. We are pursuing such questions with healthy adults and with patients who have had strokes affecting object selection abilities.

In another study, we are exploring whether common objects and unfamiliar, novel shapes call forth a particular action with the hand, and whether this association between objects and actions may be disrupted after stroke.

For example, the round, smooth shape of a hammer's handle is very well suited to a grasping action. In addition, we know through our experience with hammers that one grasps them. A thin, tall, pencil-like block shape elicits a pinching action. We are investigating whether or not individuals grasp objects because of their shape, or if these are learned actions. We are also learning if these actions are disrupted in patients who have trouble gesturing and using objects after stroke.

Previous studies under this grant have explored:

• Whether disorders of spatial attention (spatial neglect) are associated with asymmetries in the object selection processes described above;

• Whether knowledge of object manipulation may be impaired in patients with apraxia; and

• Whether disorders of an internal map of the position of the body in space may be disrupted in several disorders of the parietal lobes of the brain.