Effects of motivationally salient stimuli on visual spatial attention: Behavior and electrophysiology

Attention serves as a mediator between motivation and action by enabling the selection of goal-related information for enhanced processing at the expense of other information. Attentional biases toward food- and smoking-related stimuli may constitute an important mediator of feeding and smoking behavior, respectively, and in the latter case may play a significant role in nicotine dependence. To test for such biases, reaction time (RT) and event-related potential (ERP) measures were used to assess the impact of motivationally salient stimuli (food words in normal food-deprived individuals and smoking words in tobacco-deprived smokers) used as spatial cues that frequently predicted the location of targets in a simple detection task. RTs to targets are typically faster in such tasks when cues draw attention to the correct location (valid trials), and slower when cues draw attention to the wrong location (invalid trials). In parallel, early ERP components (P1/N1) have greater amplitude on valid trials than invalid trials, suggesting enhanced perception. It was hypothesized that motivationally salient (versus neutral) stimuli would evoke a larger P3-like late positivity due to their motivational salience and that they would magnify the classic validity effect on RT and P1/N1 amplitude due to an attentional bias. Experiment I: fasting and nonfasting subjects showed an attentional bias toward food-related words via RT. Experiment II: the RT effect was replicated in fasting subjects and found to result predominantly from an increased cost of invalid cueing by food words. The amplitude of a P3-like late positivity (P420) and an anterior N1 (100--180 ms) was enhanced in response to food words. Target-evoked P1/N1 components were not affected. Experiment III: no attentional bias was revealed by RT of deprived smokers when smoking words served as cues. There also was no difference in the target-evoked P1/N1, but there were increases in the amplitude of both the P2 and a late positivity (P410). Findings demonstrate a food-related attentional bias in normal subjects and potential electrophysiological correlates of motivational salience for both food and smoking words in deprived subjects. This research contributes to our understanding of the neurocognitive mechanisms underlying normal and maladaptive motivated behavior.