Spatial Frequency Influences The Multi-level Processing Of Face Emotions

Spatial frequency,a component underlying the processing of visual information,can have a significant impact on the processing of features and configurations of face emotions at multiple levels.Since the visual system usually has difficulty in discriminating between fear and surprise emotions due to the high degree of confusion between the two in terms of physical features,facial action units and concepts,the present study explored the multilevel processing of face emotions by spatial frequency through a series of behavioural and two EEG experiments.Behavioural Experiment 1 used the emotion recognition task to investigate the information sources of ambiguous emotion processing without disrupting the low-level integrity of faces.The results found that there were significant differences in feature recognition for both fear and surprise emotional faces in the high spatial frequency condition,while there were no significant differences in the accuracy of mouth and eye feature regions or whole face recognition for surprise and fear emotional faces in the low spatial frequency condition.Experiments 2 and 3 used the fast periodic visual stimulation(FPVS)paradigm and its variants by EEG technique,using ssVEP as an indicator.Experiment 2 used neutral and surprised faces at spatial frequencies as baseline stimuli and fearful emotions as target stimuli.The results showed that the SNR and amplitude of the low spatial frequency faces were significantly higher than those of the high spatial frequency and full spectrum conditions,and that the right hemisphere occipitotemporal region was more responsive to the stimuli when the whole face was presented.Experiment 3 added the face feature factor and chose the mixed emotion FPVS paradigm to explore the neural mechanisms underlying high-level face feature processing.The results of the study further corroborated the results of Experiments 1and 2,finding that the SNR and amplitude were significantly greater in the eye region than in the whole face in the high spatial frequency condition,while the differences between feature and configuration processing were not significant in the broad spatial frequency condition.In summary,the following conclusions were concluded from this study.(1)The similarity of eye regions can cause difficulties in the recognition of fear and surprise emotions,and the source of information to distinguish between the two emotions relies mainly on mouth regions..(2)The processing of information about the features of ambiguous emotional faces relies on high spatial frequency information,and low spatial frequencies are more sensitive to low levels of information processing.(3)Face recognition of ambiguous emotions can lose processing dominance in the right hemisphere occipitotemporal region.(4)The FPVS paradigm applies primarily to low levels of visual information processing,whereas the mixed emotion FPVS paradigm may involve higher levels of processing of facial emotion features.