The influence of frontal alpha-asymmetry on the processing of approach- and withdrawal-related stimuli-A multichannel psychophysiology study

The approach-withdrawal model of hemispheric activation suggests that left frontal cortical areas mediate approach, while right frontal cortical areas mediate withdrawal motivation. Within this framework, the present study investigates the association of frontal cortical asymmetry with attentional and emotional responses toward approach- and withdrawal-related emotional stimuli. Resting frontal asymmetry was measured from 43 students before they passively viewed negative, neutral, and positive emotional pictures. The startle reflex, skin conductance response, and subjective ratings of valence and arousal were assessed to quantify emotional responding, while attention was assessed with ERPs. We also assessed frontal asymmetry in response to the pictures. Results indicated that relatively stronger right frontal cortical activation was associated with increased N1 amplitudes and more negative subjective emotional evaluation of all stimuli. Furthermore, enhanced right frontal asymmetry (state and trait) was associated with diminished emotional modulation of the late positive potential. In contrast, no association of frontal asymmetry with defensive reflex physiology or activation of sympathetic nervous system activity was found. The current data suggest dissociable influence of resting frontal brain asymmetry on attentional and physiological processing of withdrawal- and approach-related stimuli. That is, asymmetrical frontal cortical brain activation might not modulate approach-/withdrawal-related motor responses and sympathetic arousal directly, but instead enhances allocation of attentional resources to subjectively significant stimuli. The results are discussed in terms of their potential importance for emotion perception in anxiety disorders and their contribution to the understanding of frontal asymmetry.