Audiovisual Emotional Congruency Modulates the Stimulus-Driven Cross-Modal Spread of Attention

It has been reported that attending to stimuli in visual modality can spread to task-irrelevant but synchronously presented stimuli in auditory modality, a phenomenon termed the cross-modal spread of attention, which could be either stimulus-driven or representation-driven depending on whether the visual constituent of an audiovisual object is further selected based on the object representation. The stimulus-driven spread of attention occurs whenever a task-irrelevant sound synchronizes with an attended visual stimulus, regardless of the cross-modal semantic congruency. The present study recorded event-related potentials (ERPs) to investigate whether the stimulus-driven cross-modal spread of attention could be modulated by audio-visual emotional congruency in a visual oddball task where emotion (positive/negative) was task-irrelevant. The results first demonstrated a prominent stimulus-driven spread of attention regardless of audio-visual emotional congruency by showing that for all audiovisual pairs, the extracted ERPs to the auditory constituents of audiovisual stimuli within the time window of 200-300 ms were significantly larger than ERPs to the same auditory stimuli delivered alone. However, the amplitude of this stimulus-driven auditory Nd component during 200-300 ms was significantly larger for emotionally incongruent than congruent audiovisual stimuli when their visual constituents' emotional valences were negative. Moreover, the Nd was sustained during 300-400 ms only for the incongruent audiovisual stimuli with emotionally negative visual constituents. These findings suggest that although the occurrence of the stimulus-driven cross-modal spread of attention is independent of audio-visual emotional congruency, its magnitude is nevertheless modulated even when emotion is task-irrelevant.