Event-related potentials in humans for emotional words versus pictures

Issue: 
2014
Institution: 
Roanoke College, Salem, Virginia

Along with self-reported emotional reactions, changes in brain activity occur when someone is
exposed to emotionally-charged images related to pleasure and disgust, such as baby animals and
flesh wounds. Previous studies have shown that event-related potentials (ERPs) are enhanced
separately by emotional pictures and emotional words, but none have yet to consider related
pictures and words in the same study. This study examined the effects that stimulus type and
level of emotional valence had on brain activity. Electroencephalography (EEG) was used to
record P300 and late positive potential (LPP) activity of 21 undergraduate students. Two
stimulus types were used (pictures and words), and three levels of emotionality were also used
(positive, neutral, and negative). Analysis showed that pictures generated higher magnitude
P300 and LPP peaks as compared to words for all emotional states. In the channel involving the
occipital lobe, which is responsible for basic visual processing, results showed an effect for
stimulus type but not for emotionality. The second channel, involving an electrode over the
parietal lobe (a brain area participating in emotional processing), revealed an effect associated
with positive and negative stimuli compared to neutral stimuli, with the magnitude of the effect
depending on stimulus type. It was found that pictures consistently led to a greater emotional
response compared to related words. Further analysis took into consideration the possibility of
individual differences in self-reported arousal in the LPP time range, though no significant
effects based on individual differences were found on the magnitude of the LPP. The continued
presence of main effects of stimulus type, however, was indicative of differential neural
processing of pictures versus words. Overall the results indicated larger magnitude changes in
brain activity when pictures were used as visual stimuli compared to related words, both in
regards to basic visual processing and emotional processing.

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