Emotional and movement-related body postures modulate visual processing

Abstract

Human body postures convey useful information for understanding others' emotions and intentions. To investigate at which stage of visual processing emotional and movement-related information conveyed by bodies is discriminated, we examined event-related potentials elicited by laterally presented images of bodies with static postures and implied-motion body images with neutral, fearful or happy expressions. At the early stage of visual structural encoding (N190), we found a difference in the sensitivity of the two hemispheres to observed body postures. Specifically, the right hemisphere showed a N190 modulation both for the motion content (i.e. all the observed postures implying body movements elicited greater N190 amplitudes compared with static postures) and for the emotional content (i.e. fearful postures elicited the largest N190 amplitude), while the left hemisphere showed a modulation only for the motion content. In contrast, at a later stage of perceptual representation, reflecting selective attention to salient stimuli, an increased early posterior negativity was observed for fearful stimuli in both hemispheres, suggesting an enhanced processing of motivationally relevant stimuli. The observed modulations, both at the early stage of structural encoding and at the later processing stage, suggest the existence of a specialized perceptual mechanism tuned to emotion- and action-related information conveyed by human body postures.

Keywords: N190; body postures; early posterior negativity (EPN); emotion perception; visual structural encoding.

Fig. 1

Graphical representation of the trial structure in the behavioral task. The figure depicts example trials with stimuli showing fearful (A), happy (B), neutral (C) and static body postures (D).

Fig. 2

Grand-average ERPs elicited by fearful, happy, neutral and static body postures. ERP waveforms at the representative electrodes P8 (A,B) and P7 (C,D) when stimuli were presented in the LVF (A,C) and in the RVF (B,D).

Fig. 3

Mean N190 amplitude elicited by fearful, happy, neutral and static body postures from electrode P8 in the right hemisphere (A, B) and electrode P7 in the left hemisphere (C, D) when stimuli were presented in the LVF (A, C) and in the RVF (B, D). Scalp topographies of the difference in mean N190 amplitude between fearful and other body stimuli (happy, neutral and static) when stimuli were presented in the LVF (E) and in the RVF (F) in a time window of 160–230 ms. (G) and (H) represent scalp topographies of the mean N190 amplitude averaged for all body stimuli (fearful, happy, neutral and static body postures) in a time window of 160–230 ms when stimuli were presented in the LVF and RVF, respectively. Error bars represent standard error of the mean (SEM). LF, left fearful body posture; LH, left happy body posture; LF, left neutral body posture; LS, left static body posture; RF, right fearful body posture; RH, right happy body posture; RN, right neutral body posture; RS, right static body posture.

Fig. 4

Mean EPN amplitude elicited by fearful, happy, neutral and static body postures from electrode P8 in the right hemisphere (A, B) and electrode P7 in the left hemisphere (C, D) when stimuli were presented in the LVF (A, C) and in the RVF (B, D). Scalp topographies of the difference in mean EPN amplitude between fear and other body stimuli (happy, neutral and static) when stimuli were presented in the LVF (E) and in the RVF (F) in a time window of 290–390 ms. Scalp topographies of the difference in mean EPN amplitude between static and other body stimuli (happy, neutral) when stimuli were presented in the LVF (G) and in the RVF (H) in a time window of 290–390 ms. Error bars represent standard error of the mean (SEM). LF, left fearful body posture; LH, left happy body posture; LF, left neutral body posture; LS, left static body posture; RF, right fearful body posture; RH, right happy body posture; RN, right neutral body posture; RS, right static body posture.