Abstract
Microstate analysis applied to electroencephalographic signals (EEG) allows both temporal and spatial imaging exploration and represents the activity across the scalp. Despite its potential usefulness in understanding brain activity during a specific task, it has been mostly exploited at rest. We extracted EEG microstates during the presentation of emotional expressions, presented either unilaterally (a face in one visual hemifield) or bilaterally (two faces, one in each hemifield). Results revealed four specific microstate’s topographies: (i) M1 involves the temporal areas, mainly in the right hemisphere, with a higher occurrence for stimuli presented in the left than in the right visual field; (ii) M2 is localized in the left temporal cortex, with higher occurrence and coverage for unilateral than bilateral presentations; (iii) M3, with a bilateral temporo-parietal localization, shows higher coverage for bilateral than unilateral presentation; (iv) M4, mainly localized in the right fronto-parietal areas and possibly representing the hemispheric specialization for the peculiar stimulus category, shows higher occurrence and coverage for unilateral stimuli presented in the left than in the right visual field. These results suggest that microstate analysis is a valid tool to explore the cerebral response to emotions and can add new insights on the cerebral functioning, with respect to other EEG markers.
Highlights
IntroductionFaces was contradictory enough to prevent conclusively clarifying the role of the two halves of the brain in emotion processing (see a lso[13,14])
By using the same divided visual field described above, during EEG recording, we reported that the P1 component showed a higher amplitude in the right than in the left hemisphere during the unilateral presentation of emotional faces, regardless of the positive or negative valence, and that the P2 component showed a higher amplitude in the right hemisphere for both unilateral and bilateral presentations of emotional faces, confirming the main involvement of the right hemisphere in all emotion processing[22]
In the same study we reported that the emotional judgments expressed by participants in the task were more positive for emotional faces presented in the Right Visual Field (RVF) and more negative for emotional faces presented in the Left Visual Field (LVF), regardless of their happy or angry e xpression[22], providing evidence for a valence-specific specialization of the cerebral hemispheres
Summary
Faces was contradictory enough to prevent conclusively clarifying the role of the two halves of the brain in emotion processing (see a lso[13,14]). Gianotti et al.[29] applied microstates analysis to a paradigm with emotional stimuli, and they found microstate differences from 140 to 330 ms for valence and from 300 to 520 ms for arousal (with respect to the stimulus onset), a result that extended previous knowledge obtained exploiting classical ERP analysis Starting from these premises, this study aimed at applying microstate analysis to EEG data recorded during unilateral and bilateral presentation of faces expressing positive and negative emotions. Starting from the paradigm described in Prete et al.[22,30], we aimed at investigating microstates related to the presentation of one angry or happy faces presented in either the LVF or the RVF, as well as to the presentation of two emotional faces (happy and/or angry) presented one in each visual field We believe this innovative analysis approach can help to shed more light on the unresolved field of hemispheric processing of positive and negative emotional stimuli. Considering previous ERP evidence using the same paradigm[22], we expected to find a stronger right-hemispheric involvement in emotion processing, in accordance with the RHH
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
