RESUMO
BACKGROUND: Theory of Mind (ToM), the ability to attribute mental states to oneself and others, is frequently impaired in Autism Spectrum Disorder (ASD) and may result from altered activation of social brain regions. Conversely, Typically Developing (TD) individuals overextend ToM and show a strong tendency to anthropomorphize and interpret biological motion in the environment. Less is known about how the degree of anthropomorphism influences intentional attribution and engagement of the social brain in ASD. OBJECTIVE: This fMRI study examines the extent of anthropomorphism, its role in social attribution, and the underlying neural responses in ASD and TD using a series of human stick figures and geometrical shapes. METHODS: 14 ASD and 14 TD adults watched videos of stick figures and triangles interacting in random or socially meaningful ways while in an fMRI scanner. In addition, they completed out-of-scanner measures of ToM skill and real-world social deficits. Whole brain statistical analysis was performed for regression and within and between group comparisons of all conditions using SPM12's implementation of the general linear model. RESULTS: ToM network regions were activated in response to social movement and human-like characters in ASD and TD. In addition, greater ToM ability was associated with increased TPJ and MPFC activity while watching stick figures; whereas more severe social symptoms were associated with reduced right TPJ activation in response to social movement. CONCLUSION: These results suggest that degree of anthropomorphism does not differentially affect social attribution in ASD and highlights the importance of TPJ in ToM and social attribution.
RESUMO
Understanding the meaning of others' actions involves mentally simulating those actions by oneself. Embodied theories of language espouse a prominent role for motor simulation in reading comprehension, especially when words, sentences, or narratives portray everyday actions. Inherent in these actions is the level of agency of the actor. Motor cortex activity in response to processing action verbs has been relatively well-established. What has been less explored, however, are: (1) the neural bases of determining whether an action is intentional or accidental (agency); and (2) whether agency influences level of motor simulation. This functional MRI study investigated how language and motor areas of the brain respond to sentences depicting intentional versus accidental action. 25 healthy adults read a series of sentences in the MRI scanner and determined whether the actions described were accidental or intentional. The main results include: (1) left hemisphere language areas (left inferior frontal gyrus, LIFG; left superior temporal gyrus, LSTG), premotor cortex (PM), and presupplementary motor area (pSMA) were strongly activated by both sentence types; (2) processing accidental action, relative to intentional action, elicited greater activity in LIFG, medial prefrontal cortex (MPFC), and left amygdala; no statistically significant activity was found in the opposite contrast; and (3) greater percent signal change was observed in LIFG while processing accidental action and in right precentral gyrus for intentional action. The results of this study support language and motor region involvement in action sentence comprehension in accordance with embodiment theories. Additionally, it provides new insight into the linguistic, integrative, and emotional demands of comprehending accidental action, its underlying neural circuitry, and its relationship to intentionality bias: the predisposition to ascribe purpose to action.
