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Seeing or imagining others in pain may activate both the sensory and affective components of the neural network (pain matrix) that is activated during the personal experience of pain. Transcranial magnetic stimulation (TMS), proved adept at highlighting the sensorimotor side of empathy for pain in studies where mere observation of needles penetrating body parts of a human model brought about a clear corticospinal motor inhibition. By using TMS, we investigated whether inferring the sensory properties of the pain of a model influenced the somatomotor system of an onlooker. Moreover, we tested the possible lateralization of the motor substrates underlying this reading process. We recorded motor-evoked potentials (MEPs) to left and right motor cortex stimulation during the observation of "flesh and bone" painful stimulations of right and left hands respectively. We found a significant reduction of onlookers' MEPs amplitudes specific to the muscle penetrated in the model. Subjective inferences about localization and intensity of the observed pain were associated with specific patterns of motor modulation with larger inhibitory effects following stimulation of the left motor cortex. Thus, results indicate that the mental simulation of the sensory qualities of others' pain may be lateralized to the left hemisphere.

BackgroundDespite the fact that deficits in social communication and interaction are at the core of Autism Spectrum Conditions (ASC), no study has yet tested individuals on a continuum from neurotypical development to autism in an on-line, cooperative, joint action task. In our study, we aimed to assess whether the degree of autistic traits affects participants' ability to modulate their motor behavior while interacting in a Joint Grasping task and according to their given role.MethodsSixteen pairs of adult participants played a cooperative social interactive game in which they had to synchronize their reach-to-grasp movements. Pairs were comprised of one ASC and one neurotypical with no cognitive disability. In alternate experimental blocks, one participant knew what action to perform (instructed role) while the other had to infer it from his/her partner’s action (adaptive role). When in the adaptive condition, participants were told to respond with an action that was either opposite or similar to their partner. Participants also played a non-social control game in which they had to synchronize with a non-biological stimulus.ResultsIn the social interactive task, higher degree of autistic traits predicted less ability to modulate joint action according to one’s interactive role. In the non-social task, autistic traits did not predict differences in movement preparation and planning, thus ruling out the possibility that social interactive task results were due to basic motor or executive function difficulties. Furthermore, when participants played the non-social game, the higher their autistic traits, the more they were interfered by the non-biological stimulus.ConclusionsOur study shows for the first time that high autistic traits predict a stereotypical interaction style when individuals are required to modulate their movements in order to coordinate with their partner according to their role in a joint action task. Specifically, the infrequent emergence of role-based motor behavior modulation during on-line motor cooperation in participants with high autistic traits sheds light on the numerous difficulties ASC have in nonverbal social interactions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-017-0141-0) contains supplementary material, which is available to authorized users.

Background Face individual identity recognition skill is heritable and independent of intellectual ability. Difficulties in face individual identity recognition are present in autistic individuals and their family members and are possibly linked to oxytocin polymorphisms in families with an autistic child. While it is reported that developmental prosopagnosia (i.e., impaired face identity recognition) occurs in 2–3% of the general population, no prosopagnosia prevalence estimate is available for autism. Furthermore, an autism within-group approach has not been reported towards characterizing impaired face memory and to investigate its possible links to social and communication difficulties. Methods The present study estimated the prevalence of prosopagnosia in 80 autistic adults with no intellectual disability, investigated its cognitive characteristics and links to autism symptoms’ severity, personality traits, and mental state understanding from the eye region by using standardized tests and questionnaires. Results More than one third of autistic participants showed prosopagnosia. Their face memory skill was not associated with their symptom’s severity, empathy, alexithymia, or general intelligence. Face identity recognition was instead linked to mental state recognition from the eye region only in autistic individuals who had prosopagnosia, and this relationship did not depend on participants’ basic face perception skills. Importantly, we found that autistic participants were not aware of their face memory skills. Limitations We did not test an epidemiological sample, and additional work is necessary to establish whether these results generalize to the entire autism spectrum. Conclusions Impaired face individual identity recognition meets the criteria to be a potential endophenotype in autism. In the future, testing for face memory could be used to stratify autistic individuals into genetically meaningful subgroups and be translatable to autism animal models.