Facial EMG Correlates of Subjective Hedonic Responses During Food Consumption

Abstract

An exploration of physiological correlates of subjective hedonic responses while eating food has practical and theoretical significance. Previous psychophysiological studies have suggested that some physiological measures, including facial electromyography (EMG), may correspond to hedonic responses while viewing food images or drinking liquids. However, whether consuming solid food could produce such subjective–physiological concordance remains untested. To investigate this issue, we assessed participants’ subjective ratings of liking, wanting, valence, and arousal while they consumed gel-type food stimuli of various flavors and textures. We additionally measured their physiological signals, including facial EMG from the corrugator supercilii. The results showed that liking, wanting, and valence ratings were negatively correlated with corrugator supercilii EMG activity. Only the liking rating maintained a negative association with corrugator supercilii activity when the other ratings were partialed out. These data suggest that the subjective hedonic experience, specifically the liking state, during food consumption can be objectively assessed using facial EMG signals and may be influenced by such somatic signals.

Facial EMG Activity Is Associated with Hedonic Experiences but Not Nutritional Values While Viewing Food Images

“…The liking ratings were negatively and positively associated with EMG activity of the corrugator supercilii [ 7 , 8 ] and zygomatic major muscles [ 7 ], respectively. Corroborating these data, other studies recorded EMG from these facial muscles while participants consumed liquid [ 9 , 10 , 11 ] or solid [ 12 ] food and showed similar associations between hedonic ratings, such as liking, wanting, and valence, and facial EMG activity of these muscles. Relatedly, some studies reported an association between facial expressions analyzed from video data and liking ratings during liquid food consumption [ 13 , 14 ].…”

“…Facial EMG signals of the corrugator supercilii, zygomatic major, masseter, and suprahyoid muscles were recorded using pre-gelled, self-adhesive silver/silver chloride (Ag/AgCl) electrodes with 0.7-cm diameter and 1.5-cm interelectrode distance (Prokidai, Sagara, Japan). The electrodes were attached according to guidelines [ 41 , 42 ] and methods in previous studies [ 12 , 31 , 32 ]. A ground electrode was set in the middle of the forehead.…”

“…Other relationships were analyzed in the same way for descriptive purposes. The intra-individual correlation coefficients were normalized using Fisher’s z -transformation and then analyzed with one-sample t -tests (two-tailed) to compare the means with zero, in accordance with previous studies that investigated subjective–physiological emotional concordance using food (e.g., [ 12 ]) and non-food (e.g., [ 45 ]) stimuli. Such a two-stage procedure has been shown to be valid as a random-effects analysis [ 46 ].…”

Dopaminergic and opioidergic regulation during anticipation and consumption of social and nonsocial rewards

“…Third, because facial responses during reward anticipation – previously shown to occur to learned cues for rewards in rats ( Delamater et al, 1986 ), and humans ( Korb et al, 2020 ) – may reflect anticipated pleasure during a period commonly associated with wanting, they were expected to be affected by naltrexone, as well as by amisulpride, compared to placebo. Finally, based on fEMG results showing similar hedonic facial reactions to food and touch rewards, such as relaxation of the corrugator supercilii muscle and in some cases activation of the zygomaticus major muscle ( Bershad et al, 2019 ; Korb et al, 2020 ; Mayo et al, 2018 ; Pawling et al, 2017 ; Ree et al, 2019 ; Sato et al, 2020 ), and on evidence from neuroimaging studies that supports the ‘common currency hypothesis’ of reward processing ( Berridge and Kringelbach, 2015 ; Ruff and Fehr, 2014 ), we expected the same pattern of results for both types of rewards.…”

“…Recently, the use of facial electromyography (fEMG) has gained increased attention in the context of human reward processing. Results suggested that human adults relax the corrugator muscle (involved in frowning), and to a lesser extent activate the zygomaticus muscle (involved in smiling), during both anticipation and consumption of different types of pleasurable stimuli, although differences between types of rewards exist ( Bershad et al, 2019 ; Franzen and Brinkmann, 2016 ; Korb et al, 2020 ; Mayo et al, 2018 ; Pawling et al, 2017 ; Rasch et al, 2015 ; Ree et al, 2019 ; Sato et al, 2020 ; Wu et al, 2015 ). Notably, to the best of our knowledge, no study has yet investigated implicit hedonic facial reactions to different types of rewards after pharmacological drug challenge in humans.…”