Body form and body motion processing are dissociable in the visual pathways

The human body is a salient communicator of social information, such as aggression, intention, and affective state. Although brain areas specializing in human body recognition have been identified, little is understood about how these areas interact and contribute to the different components of body recognition (see de Gelder et al., 2010). One model of action discrimination proposes that signals conveyed by the body are processed along two parallel pathways in the brain, a dorsal pathway analyzing body motion signals and a ventral pathway analyzing body form signals (Thompson and Baccus, 2012; Miller and Saygin, 2013) (see Figure 1A). The posterior superior temporal sulcus (pSTS) is hypothesized to be involved in processing body motion cues, while the extra-striate body area (EBA) and fusiform body area (FBA) are hypothesized to be involved in processing body form cues (Peelen et al., 2006; Grossman et al., 2010; Grosbras et al., 2012). However, dissociating these two pathways remains a contentious issue in the body recognition literature. Firstly, there is substantial cortical overlap between EBA and the human motion complex (hMT+). Secondly, body form and motion are closely linked and integrated; body motion can give clues about body form such as gender, identity and emotion (Pollick et al., 2005; Ross et al., 2012); conversely body posture conveys information about intended movement (Cazzato et al., 2012). A recent study conducted by Vangeneugden et al. published in The Journal of Neuroscience, addressed these issues in a novel way (Vangeneugden et al., 2014).