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Li, Zinbarg, and Paller (2007) used words and found the P1 (100-160 ms) amplitude difference between threat and neutral words was positively correlated to BIS trait anxiety. The P1 “tended” to be larger for high trait anxiety participants. Low anxiety participants appeared to show neutral words evoked a larger P1 than threat words. The LPP (300-500 ms) showed a larger amplitude pattern to threat words than neutral words, which was greatest at central sites. It is expected that threat words had greater arousal quality than neutral words.

Li, Zinbarg, Boehm, and Paller (2008) did report differences in P1 (145-175 ms) amplitude for happy versus fearful faces. Fearful faces evoked larger amplitude P1 than happy faces at in occipital region. The magnitude of P1 differences between fearful and happy faces was positively correlated with trait anxiety score (formed as a composite of SPS and BIS measures). The LPP pattern (300-400 ms) showed that fearful faces evoked a lower amplitude pattern than happy faces in the central region. There was not a relationship found between the LPP and trait anxiety. The face stimuli used in this study were not matched on arousal.

Holmes, Nielsen, Tipper, and Green (2009) used fearful, happy, and neutral facial expressions to evaluate the P1, EPN, and LPP in high and low anxiety participants using a 1- back and 2-back task. These tasks required participants to indicate whether the current stimulus presented matched a previous stimulus that appeared one or two presentations in the past. In frontal regions the early LPP (180-400 ms) and the late LPP (400-700 ms) were analyzed. In posterior regions the P1 (124-164 ms) the EPN (208-280 ms) were analyzed. Fearful faces evoked the largest P1, which differed from neutral faces. Happy faces evoked an intermediate amplitude P1, which did not differ from fearful or neutral faces. In the EPN window, the low anxious group showed that fearful and happy faces differed from neutral faces, but did not differ

from each other. For the early LPP window, fearful and happy faces differed from neutral, but fearful and happy did not differ from each other. The waveforms indicate the fearful and happy conditions had greater positivity than neutral faces. For the late LPP window, the 1-back task results showed that fearful faces evoked a significantly larger pattern than neutral, with happy faces again intermediate that did not differ from fearful or neutral. The 2-back task showed both fearful and happy faces evoked significantly larger patterns than neutral, but did not differ from each other.

Wangelin et al. (2012) found that the LPP (400-700 ms) was more positive for both high arousing positive and negative images (erotica, violence) than neutral scenes. Additionally, the startle LPP amplitude was lower in amplitude for these positive and negative scenes compared to neutral. There were no differences found for the LPP and LPP magnitude between high and low socially anxious groups classified using the LSAS.

Gibbons (2009) investigated subliminal priming using words presented at 17 ms to affect judgments of paintings and portrait images. The prime word varied valence (positive vs. negative) and arousal level (high vs. low). Individual differences in state and trait anxiety were measured because high anxiety has been found to increase priming effects on behavioral measures and P1 amplitude. Judgments of target images were more positive when primed by a positive word than by a negative word, and positive arousing prime words evoked more positive judgments than other conditions. In this study, high anxious participants were affected more than low anxious by the manipulation. ERP differences were not found in the early ERP patterns, however later components, such as the LPP, was more positive for positive arousing primes than negative arousing primes. The effects demonstrated that subliminal priming affected late versus early processing stages based on ERP results.

In general, when effects of anxiety were found in ERP patterns, they related to arousing positive and negative stimuli compared to neutral. A clear picture of how anxiety level affects ERP components is not apparent at this time. However, given the increased sensitivity to stimuli, especially negative stimuli, and growing interest in the neural mechanisms underlying anxiety I believe it is important to consider its role in emotional stimulus processing. It would not be surprising to find anxiety-specific effects as ERP components related to affective priming become more apparent.

Table 4. ERP Effects of Anxiety (NA)

Paper StimType Modality Task P1 N1 EPN MFN/N400 LPP

Sass (2010) words visual Stroop Anxious arousal

women > Anxious arousal men

n.a. E < NEU E > NEU NS

Gibbons (2009)

words visual Rate liking of image

NS NS n.a. n.a. POS arousing > NEG

arousing

Li (2009) faces visual Judge affect NEG > POS n.a. NS n.a. POS > NEG

Wangelin (2012)

scenes,

faces visual Passive view n.a. n.a. n.a.

P3: NEU > E; LPP: E > NEU

Li (2008) faces visual Valence

Judgment

NEG > POS n.a. n.a. n.a. POS > NEG

Li (2007) words visual Stroop NS n.a. n.a. n.a. NEG > NEU frontal in

supraliminal, posterior in subliminal Holmes

(2009)

faces visual 1-back test NEG > NEU n.a. n.a. POS & NEG > NEU

> means "more positive” or "less negative”, < means "more negative" or " less positive", ** = Did not control POS, NEG for arousal , NS = No Effect, n.a. = Not Analyzed