Research conducted in the Zaidel Lab at UCLA

1. Automatic Processing of Emotionally Salient Images
Henry Schwimmer, Erica Huang, Michelle Frias, Alex Cho, Leonardo Fernandino, Allen Azizian*, & Eran Zaidel
University of California, Los Angeles
INTRODUCTION RESULTS
•P300 is an event related potential (ERP) associated with Within-subjects ANOVA: 4 (Condition: frequent, infrequent
attentional processing in oddball detection tasks. neutral, infrequent positive, infrequent negative) x 3 (Electrode
Laterality: left, central, right) x 3 (Electrode Location: frontal,
•Discrimination of affective stimuli yields a larger P300 for central, parietal)
negative than for positive targets.
P300 P300 P300
•No main effect of emotional valence.
•Question: Is the effect of stimulus valence on the amplitude • Significant interaction between laterality and emotional
of the P300 attentional or is it automatic? valence (p <.05):
METHODS negative stimuli produced a larger P300 in the right
Participants: electrodes while
• 17 right-handed undergraduate UCLA students positive stimuli produced a larger P300 in the left electrodes.
Procedure: P300 P300 P300
•We recorded EEG data from subjects while they
performed a perceptual discrimination task.
Task:
•Discriminate between frequent and infrequent stimuli using
manual key presses.
•Frequent stimuli were presented as a large sunburst effect. P300 P300 P300
• Only neutral images were presented in the background
of frequent stimuli.
• Infrequent stimuli were presented as a small sunburst Fig. 2. ERP grand averages of all subjects: Infrequent Negative (Red), Infrequent Positive (Blue),
effect. Infrequent Neutral (Yellow), Frequent Neutral (Green).
•Positive, neutral, or negative images were presented in
Fig. 3. Interaction between laterality and picture type
the background of infrequent stimuli.
DISCUSSION AND CONCLUSIONS
• There was no significant difference between P300 amplitudes for negative and positive stimuli.
• However, there was a significant interaction between emotional valence and laterality:
electrodes over the left hemisphere produced a larger P300 for positive stimuli
whereas
electrodes over the right hemisphere produced a larger P300 for negative stimuli.
• The effect of valence on the P300 of infrequent stimuli suggest that emotional valence is
processed automatically, independently of attention allocation.
Fig. 1. Stimuli (from left to right): Frequent Neutral, Infrequent Positive, Infrequent Negative, Infrequent Neutral. • Previous developmental, lesion, and other ERP studies support the valence hypothesis of
REFERENCES hemispheric specialization of emotional stimuli (right hemisphere = negative affect, left
Davidson, R. J., Fox, N.A., 1982. Asymmetrical brain activity discriminates between positive and negative affective stimuli in human infants. hemisphere = positive affect). Our results suggest that those studies reflect automatic processes
Science 218, 1235-1237.
Olofsson, J.K., Nordin, S., Sequeria, H., Polich, J., 2008. Affective picture processing: An integrative review of ERP findings. Biological
as well.
Psychology 77, 247-265.
Polich, J., 2007. Updating P300: an integrative theory of P3a and P3b. Clinical Neurophysiology 118, 2128–2148.
• The pattern of responses in the central electrodes is the same as in the right electrodes. This
suggests dominance by the right hemisphere for processing affective stimuli.
* Corresponding author: aazizian@usc.edu