Institution: Roanoke College, Salem, Virginia
Abstract: 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.