From a planned action to a revised action: revealing the structure of motor plans




Lawless, Katie

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We examined the effect of changing from an internally prepared motor plan to a revised action which potentially differed from the original plan along two dimensions: wrist orientation (horizontal or vertical) and left/right hand. Participants were instructed to prepare a particular hand grasp action and then were cued either to execute that motor plan or cancel it and plan a new action. In Experiments I and II, if the change from the original motor plan to an alternate response implied an action different from the prepared one, there was a slowing in response time. Moreover, if there was a change, maintaining the originally planned wrist orientation produced faster responses than changing orientation, but only if the response hand remained constant between planned and alternate actions and the cue was an image of a hand depicting a goal posture. In Experiment III, when the alternate action was cued by an image of an object inviting a particular grasp action, there was transfer only of the hand feature. In a final experiment, participants switched from a prepared action to naming a manipulable object. The motor features of the object differed from the original motor plan in the same way as in previous experiments. No effect of the previously cancelled motor plan was seen on naming latencies. These results elucidate the nature of motor plans and the role of motor actions in the representation of objects.



motor plan, wrist orientation, prepared action, revised action