| Abstract No.: | B-G2201 |
| Country: | Canada |
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| Title: | DO OBJECTS WITHIN REACH PRIME THE VISUOMOTOR SYSTEM FOR ACTION? |
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| Authors/Affiliations: | 1 Jason Gallivan*; 1 Craig Chapman; 1 Jody Culham;
1 University of Western Ontario, London, ON, Canada.
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| Content: | Objectives: It is well known that graspable objects elicit affordances (Gibson, 1979). In particular, it has been suggested that such affordances can affect visuomotor processing related to potential actions that can be performed on the object. There remains, however, inconclusive evidence on whether the affordances offered by graspable objects result in either facilitation or interference of motor responses not directed toward the object (see Tucker and Ellis, 1998; Handy et al., 2003; 2007). It also remains to be seen if such effects are dependent on the object potentiating immediate actions, like in the case of reachable vs. unreachable objects. Indeed, human and macaque studies have previously shown that reachable objects elicit a unique neural representation that objects beyond reach do not (Gallivan et al., 2007; Iriki et al., 1996). The main purpose of this research is to examine the effect that both object handle orientation (affordance) and distance have on reaching kinematics and reaction times. Studies have shown that reaching trajectories are highly representative of underlying cognitive processes evolving over time (Song and Nakayama, 2007). Thus using a reaching paradigm, we wanted to address whether objects within reach prime the visuomotor system for action with the hand congruent to the orientation of an object’s handle. We hypothesize modulations in reaction times (RTs) and reach kinematics when objects are within reach and the handle is oriented toward the hand used to respond.
Materials and Methods: 24 right handed subjects were instructed to reach-to-touch two buttons on a table surface in front of them (40 cm away from a left and a right-hand start position) to indicate whether the object presented at one of two distances (40 cm and 200 cm) was upright or inverted (one response with each hand). The hand of response was counterbalanced across subjects. The handle of the object could either be oriented towards the left, right or alternatively, the object had no handle. Reach trajectories and RTs were measured using an OPTOTRAK infrared camera that tracked the position of six infrared markers, 3 attached to each of the participant’s hands.
Results: Preliminary results show slower reaction times with the right hand only when the object was within reachable space and its handle was oriented towards the right. This same effect was not observed with the left hand. This finding is consistent with an interference effect, but only for the dominant hand and when the object is reachable.
Conclusions: This study provides evidence supporting an interference of visuomotor processing related to object affordance for motor responses not directed toward the object. We suggest that not only is the visuomotor system concerned with handedness and affordance, but also whether potential hand actions can be immediately performed on the object, that is, whether the object is reachable or not.
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