It is well established that the preparation of goal directed movements such as saccades and manual reaches is accompanied by covert shifts of attention to the future target position. In the present study, we investigated the spatial deployment of attention during two- and three finger grasping of various geometric objects. The objects were attached to a vertically oriented plane and grasped with two fingers (thumb and index finger) or with three fingers (plus middle finger). The contact points with the object were self-chosen by the participant and recorded with electromagnetic sensors attached to individual fingers. In order to assess the spatial distribution of visual attention, we developed a new perceptual discrimination paradigm, the "multiple letters task". In each trial, a noise pattern surrounding the object changed into eight letters and eight distractors for 100 ms, and then post-masked by a noise pattern. The letters were chosen randomly from a larger set of 16 letters. After grasping, subjects were asked to indicate three letters they had seen during the preparation of the movement. The percentage of correctly reported letters as a function of distance from the contact positions of the individual fingers yielded the distribution of covert visual attention. The findings confirm the tight link between covert attention and movement targets also for grasping. Attention was directed to all future contact points with the object, demonstrating that multiple foci of attention are established during grasping. Our results provide evidence in favor of an "attentional landscape" that is established when more than a single location is relevant for the planning of a motor action.
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