Brain electrical correlates of emotion and attention in lexical semantic processing.

摘要

Five experiments were conducted, using event-related potentials (ERPs) to examine neural correlates of emotion and attention in semantic priming. In Experiments 1 and 2, subjects made lexical decisions to letter strings that were preceded by prime words. Associative strength was varied to examine breadth of semantic priming. Interword interval (SOA) was 800ms in Experiment 1, and 200ms in Experiment 2. Priming effects were observed across multiple components, including a left temporal N3, medial frontal MFN, parietal N400, and late positivity (LPC). Strong and weak priming effects were similar across SOAs, but elicited hemispheric differences over posterior electrodes. To clarify these effects, Experiment 3 used a delayed-probe task to minimize overlap of the N400 and LPC. As predicted, weak associates elicited N400 priming only over the right hemisphere, whereas strong associates elicited priming over both hemispheres.; To emphasize effects of automatic processing, Experiment 4 used a 67ms SOA, and prime words were visually masked in half the trials. Frontal and posterior semantic effects were observed in the masked and unmasked conditions. The pattern of results in a secondary task suggested individual differences in allocation of attention that affected frontal (MFN) priming, even in the absence of awareness.; To further explore individual differences in semantic priming, a meta-analysis was conducted. Subjects were divided into high and low Positive Affect (PA) and Negative Affect (NA) groups. Enhanced priming of weakly related words was predicted for high-PA subjects, particularly over the right hemisphere. By contrast, high-NA subjects were expected to show enhancement of strong associates over the left hemisphere, reflecting a bias towards focal attention. N400 priming showed the predicted pattern of effects. Further, the MFN was modulated by NA, consistent with previous work on medial frontal networks in anxiety.; In Experiment 5, a noise stressor was used to induce anxiety in half the experimental blocks (67ms SOA). MFN effects showed a pattern reminiscent of the Yerkes-Dodson Law: moderately trait-anxious subjects showed robust MFN priming, while these effects were virtually absent for the high and low trait-anxious subjects. These results provide unequivocal evidence for "bottom-up" effects of emotion and arousal in semantic processing.