A Review on the Role of Affective Stimuli in Event-Related Frontal Alpha Asymmetry

Abstract

Frontal alpha asymmetry refers to the difference between the right and left alpha activity over the frontal brain region. Increased activity in the left hemisphere has been linked to approach motivation and increased activity in the right hemisphere has been linked to avoidance or withdrawal. However, research on alpha asymmetry is diverse and has shown mixed results, which may partly be explained by the potency of the used stimuli to emotionally and motivationally engage participants. This review gives an overview of the types of affective stimuli utilized with the aim to identify which stimuli elicit a strong approach-avoidance effect in an affective context. We hope this contributes to better understanding of what is reflected by alpha asymmetry, and in what circumstances it may be an informative marker of emotional state. We systematically searched the literature for studies exploring event-related frontal alpha asymmetry in affective contexts. The search resulted in 61 papers, which were categorized in five stimulus categories that were expected to differ in their potency to engage participants: images & sounds, videos, real cues, games and other tasks. Studies were viewed with respect to the potency of the stimuli to evoke significant approach-avoidance effects on their own and in interaction with participant characteristics or condition. As expected, passively perceived stimuli that are multimodal or realistic, seem more potent to elicit alpha asymmetry than unimodal stimuli. Games, and other stimuli with a strong task-based component were expected to be relatively engaging but approach-avoidance effects did not seem to be much clearer than the studies using perception of videos and real cues. While multiple factors besides stimulus characteristics determine alpha asymmetry, and we did not identify a type of affective stimulus that induces alpha asymmetry highly consistently, our results indicate that strongly engaging, salient and/or personally relevant stimuli are important to induce an approach-avoidance effect.

Alpha‐band oscillations and emotion: A review of studies on picture perception

“…Pönkänen & Hietanen, 2012;Poole & Gable, 2014;Uusberg et al, 2014; for reviews, seeSabu et al, 2022). Consistently, most of the studies examined in the present review did not report any hemispheric difference in alpha activity for pleasant and unpleasant stimuli, and neuroimaging studies (fMRI and PET) failed to find asymmetrical frontal activation differences as a function of type of affective stimuli(García-García et al, 2016;Kober et al, 2008;Murphy et al, 2003;Pizzagalli et al, 2003;Xu et al, 2021;Wager et al, 2015).…”

“…Several studies examined frontal alpha asymmetry as an individual difference variable (resting activity) related to emotional responses and disorders (for reviews on this specific topic see Coan & Allen, 2004; Davidson, 1992; Hagemann, 2004; Harmon‐Jones & Gable, 2018; Reznik & Allen, 2018). Concerning frontal alpha asymmetry as a state‐dependent concomitant of emotional responding (“activation”) to visual stimuli, the studies failed to observe any effect of emotional picture content (Adolph et al, 2017; Deng et al, 2021; Elgavish et al, 2003; Gable & Harmon‐Jones, 2008; Güntekin et al, 2017; Hagemann et al, 1998; Harmon‐Jones, 2007, Harmon‐Jones et al, 2010; Harmon‐Jones et al, 2022; Pönkänen & Hietanen, 2012; Poole & Gable, 2014; Uusberg et al, 2014; for reviews, see Sabu et al, 2022). Consistently, most of the studies examined in the present review did not report any hemispheric difference in alpha activity for pleasant and unpleasant stimuli, and neuroimaging studies (fMRI and PET) failed to find asymmetrical frontal activation differences as a function of type of affective stimuli (García‐García et al, 2016; Kober et al, 2008; Murphy et al, 2003; Pizzagalli et al, 2003; Xu et al, 2021; Wager et al, 2015).…”

Commentary: A review on the role of affective stimuli in event-related frontal alpha asymmetry

“…This commentary addresses the discrepancies in measuring and interpreting frontal alpha asymmetries (FAAs) as electrophysiological makers for motivation and affect identified by a recent review (Sabu et al, 2022). Specifically, the authors aim to identify under which circumstances FAAs yield meaningful results and index emotional or motivational states.…”

Emotional dampening in hypertension: Impaired recognition of implicit emotional content in auditory and cross‐modal stimuli

“…These researchers have speculated this frontal asymmetry (an enhanced activation of the left relative to right frontal cortex) to be a possible mechanism mediating BP and emotional dampening. Since greater left compared to right frontal activation is linked to behavioral tendencies of approach (see review by Sabu et al, 2022 ), this implies that cardiovascular emotional dampening may be associated with enhanced behavioral approach tendencies, such as risk‐taking behaviors (e.g., rash driving, excessive drug use, and gambling; Loveless et al, 2018 ). Relatedly, emotional dampening has been reported to possibly mediate the relationship of high BP and increased risk‐taking behavior (McCubbin et al, 2018 ) due to a reduced appraisal of threat.…”