Abstract
Recent evidence demonstrates that attentional allocation is sensitive to monetary reward (Kristjansson et al., 2005, 2010). What remains to be explored is the extent to which reward-based orienting influences attentional allocation. We examined whether visuo-spatial neglect, a deficit of attention to the left side of space, is sensitive to an imposed reward-based structure. Several studies suggest that a necessary component to improving attentional allocation in neglect is having a top-down goal (Snow & Mattingley, 2006). Therefore, the aim of the current study is to influence attentional allocation by biasing the neglected side with reward. Subjects completed a pop-out search task in which one of three diamonds was a color singleton. The task was to report the location (top or bottom) of a missing notch on the singleton. One color was designated as the high reward stimulus, while the other was low reward. Color, and therefore reward level, could repeat or switch on every trial. Control participants exhibited effects of reward (faster reaction time for highly rewarded color) and of repetition (decreasing reaction time as the number of repetitions increased). In patients, with no reward structure, we found large differences in reaction time between the left and right sides, serving as the baseline level of neglect. To examine flexibility of attention, patients completed a color reward condition (same as controls) and a left side reward condition in which reward biased the left side of the display. The same RT differences were present with color reward, but decreased significantly in the left side reward condition indicating that attentional allocation was influenced by reward. The change in allocation of spatial attention indicates that reward can be used as a rehabilitative tool for neglect patients. These results provide strong evidence for the flexibility of attention and the possibility of plasticity and recovery after stroke.