Impact of body posture on laterality judgement and explicit recognition tasks performed on self and others’ hands

Abstract

Judgments on laterality of hand stimuli are faster and more accurate when dealing with one's own than others' hand, i.e. the self-advantage. This advantage seems to be related to activation of a sensorimotor mechanism while implicitly processing one's own hands, but not during explicit one's own hand recognition. Here, we specifically tested the influence of proprioceptive information on the self-hand advantage by manipulating participants' body posture during self and others' hand processing. In Experiment 1, right-handed healthy participants judged laterality of either self or others' hands, whereas in Experiment 2, an explicit recognition of one's own hands was required. In both experiments, the participants performed the task while holding their left or right arm flexed with their hand in direct contact with their chest ("flexed self-touch posture") or with their hand placed on a wooden smooth surface in correspondence with their chest ("flexed proprioceptive-only posture"). In an "extended control posture", both arms were extended and in contact with thighs. In Experiment 1 (hand laterality judgment), we confirmed the self-advantage and demonstrated that it was enhanced when the subjects judged left-hand stimuli at 270° orientation while keeping their left arm in the flexed proprioceptive-only posture. In Experiment 2 (explicit self-hand recognition), instead, we found an advantage for others' hand ("self-disadvantage") independently from posture manipulation. Thus, position-related proprioceptive information from left non-dominant arm can enhance sensorimotor one's own body representation selectively favouring implicit self-hands processing.

Whose hand is this? Differential responses of right and left extrastriate body areas to visual images of self and others’ hands

“…Previous studies on the hand laterality task performed on self or others' hands reported a self-advantage (Conson et al, 2015;Ferri et al, 2012;Ferri et al, 2011). This selfadvantage seems to be related to activation of left vPM that, instead, is not recruited when explicitly recognizing one's own hands (Ferri et al, 2012).…”

“…In Experiment 1 we did not find evidence of a self-advantage but speeded judgments on others' hands (i.e., self-disadvantage) during right EBA stimulation. Since previous behavioral experiments on explicit visual recognition of self and others' hands demonstrated a selfdisadvantage (Conson et al, 2015;Ferri et al, 2011; but see Conson, Aromino, & Trojano, 2010), in the present experiment, rTMS of right EBA and left vPM was applied to test whether stimulation of right EBA could also enhance explicit visual recognition of others' hands.…”

“…In the first experiment, rTMS of right EBA and left vPM was applied while participants performed an implicit body identity processing task (i.e., the laterality judgment task on self or others' hand images; Conson et al, 2015;Ferri et al, 2012;Ferri et al, 2011). To find that right EBA stimulation affects responses to identity or perspective of observed hands would demonstrate its involvement in extracting identity information from body parts (Chan et al, 2004;Jeannerod, 2004;Myers & Sowden, 2008;Ramsey et al, 2011;Saxe et al, 2006;Urgesi et al, 2007).…”

“…In the present study, in two experiments we tested the role of right EBA and left vPM in self-other distinction by combining on-line high frequency repetitive transcranial magnetic stimulation (rTMS) with behavioral tasks requiring participants to judge laterality of either self or others' hands (implicit self-hand processing; Experiments 1) or to explicitly recognize their own hands (Experiment 2; Conson et al, 2015;Ferri et al, 2012;Ferri, Frassinetti, Costantini, & Gallese, 2011). In Experiment 3, we ascertained possible functional specialization in self-other distinction of the left and right EBA by online rTMS applied while participants performed the hand laterality task with implicit identity processing.…”

Mental simulation of drawing actions enhances delayed recall of a complex figure

“…keeping a specific posture of one's own arms/hands) can affect behavioural performance on tasks implying motor simulation (e.g. the hand laterality task) in an effector-specific way, thus supporting a simulation view of motor imagery: more precisely, keeping a right (left) arm/hand in an awkward posture could impair participants' judgments on right (left)-hand stimuli with respect to comfortable hand postures (Conson et al 2011(Conson et al , 2015(Conson et al , 2016de Lange et al 2006;Ionta and Blanke 2009). We capitalized on these findings and assessed whether specific postures (i.e.…”