Visual responses to action between unfamiliar object pairs modulate extinction.

Previous studies show that positioning familiar pairs of objects for action ameliorates visual extinction in neuropsychological patients (Riddoch, Humphreys, Edwards, Baker, & Willson, 2003). This effect is stronger when objects are viewed from a self-perspective and are placed in locations congruent with the patient's premorbid handedness (Humphreys, Wulff, Yoon, & Riddoch, 2010a), consistent with it being modulated by a motor response to the stimuli. There is also some evidence that extinction can be reduced with unfamiliar object pairs positioned for action (Riddoch et al. 2006), but the effects of reference frame and hand-object congruence have not been examined with such items. This was investigated in the present experiment. There was greater recovery from extinction when objects were action-related compared to when they were not, in line with previous studies. In addition, patients benefited more when they saw action-related pairs from a third-person than from a first-person perspective. Interestingly, on trials where extinction occurred, there was a bias reporting the 'active' object on the extinguished side-a reversal of the standard pattern of extinction-but only when objects were seen from a self-perspective. The data show that several factors contribute to the effects of action relations on attention, depending upon the familiarity of the object pairs and the reference frame that stimuli have been seen in.