Affective motivational direction drives asymmetric frontal hemisphere activation.

Decades of research have shown that the left- and right-frontal cortical regions are asymmetrically involved in affective processing. Specifically, this past work has demonstrated that greater left-frontal activation is related to positive-approach, and greater right-frontal activation is related to negative-withdrawal. However, much of this past work confounded motivation and affective valence. The current experiment sought to illuminate whether frontal asymmetry is related to motivation or affective valence by examining frontal-lateralized late positive potentials (f-LPPs) and frontal cortical alpha power activation to approach-positive, approach-negative, and withdrawal-negative affects in the same participants. Results revealed that f-LPPs to approach-positive and approach-negative pictures were larger in left- (vs. right-) frontal regions, whereas f-LPPs to withdrawal-negative pictures did not differ between frontal regions. In addition, midline LPPs to approach-positive and approach-negative pictures related to greater left-frontal cortical activation. Together, these results suggest that greater relative left-frontal activation is associated with positive and negative approach-motivated states in the same participants. More broadly, these results are consistent with conceptual models that asymmetric hemisphere activation is related to motivational direction, rather than affective valence.