The Neural Correlates Of Theory Of Mind

Theory of mind(ToM)refers to the ability to attribute mental states(desires,beliefs,intentions,emotion,etc.)to self and others,and predict actions in terms of these mental states.As an important aspect of social cognition,acquisition of ToM is indispensable for living,adaptation,and development in human society.Although there are plenty of studies have explored the way in which ToM develops and operates,some of them even built models for the processing,it is still unclear how certain kinds of processing occur in ToM operation.Therefore,the event-related potential(ERP)methodology has increasingly been used in ToM research because of its high temporal resolution.However,existing ERP studies mainly focused on one aspect of ToM,mostly the belief of others.Studies on one's own mental state,which is also an intrinsic part of ToM concept,are rare.Furthermore,the results have not been discussed under the interpretative models of Tom processing.The present thesis used electrophysiological methods to reveal the substrates of ToM by recording ERPs while participants conducted mental states reasoning,including desires,beliefs,intentions,and emotion,and compared the neural correlates of mental states reasoning for self to those for other people.Exploring the neural substrate of mental states reasoning for different objects is an important step to facilitate the interpretation of the underlying cognitive process of ToM more comprehensively and also provides electrophysiological evidence to examine the theoretical mechanisms of ToM.The present thesis contained four studies which connected with each other.The first study compared the neural activity elicited by desire reasoning for self and for others under consistent or inconsistent conditions by using the event-related potential method.The results revealed that the late positive component(LPC)associated with desire reasoning was larger during the 450-550 ms time period in the condition of reasoning for self than that for others when desires were inconsistent.A left hemisphere effect on the scalp distribution was observed for the LPC component.This study showed that a left frontal LPC component might reflect the subjective categorization process in desire reasoning.The second study compared the time course of neural activity associated with belief reasoning for self and for others when the belief belonging to self was consistent or inconsistent with others.Results showed that during a 450-600 ms period,belief reasoning for self elicited a larger LPC than for others when beliefs were inconsistent with each other.The LPC divergence is assumed to reflect the categorization of agents in ToM processes.The third study compared the neural activity elicited by intention reasoning for self and for others when the intention matched or mismatched the desire of the agent.The results revealed that three ERP components distinguished among different types of intention reasoning.A negative-going ERP deflection with right frontal distribution between 400 and 500 ms might reflect the cognitive conflict involved in desire processing,a right frontal late positive component might be associated with the categorization of agents,and a centro-parietal late slow wave(LSW)might indicate the conceptual mental operations associated with decoupling mechanisms in intention processing.The fourth study compared the neural activity elicited by emotion reasoning for self and for others when emotion of the agent was pleasant or unpleasant.Results showed that N2 elicited by emotion reasoning was more negative when the emotion belonging to self was pleasant than that was unpleasant.The N2 divergence might reflect that more attentional resources were recruited during the negative emotion processing compared to positive emotion processing.Additionally,a larger LSW(500-800 ms)was elicited by unpleasant emotion reasoning than pleasant emotion reasoning when reasoning emotion for others.The LSW divergence might associated with the allocation of cognitive resources when understanding the emotion of others.Results of the four studies were general discussed based on three aspects including ERP components,scalp area,and processing implication.First,all kinds of mental states reasoning were associated with ERP component later than 450 ms after onset of stimulus.These findings were consistent with previous researches which mostly reported the correlation between ToM and medium or later ERP components.Second,the divergence of waveforms elicited by experimental conditions was predominantly distributed around frontal scalp areas,although the hemisphere lateralization effects were not identical in the four studies.It was consistent with plenty of previous neuroimaging studies which reported that ToM processing was associated with activity in the prefrontal cortex.It also suggested that the neural substrate of ToM processing might be a broad network of brain regions including frontal cortex rather than a single module related to ToM.Third,divergence of waveforms between mental state reasoning for self and for other was observed in neural activities elicited by desire reasoning,belief reasoning,and intention reasoning.Furthermore,it indicated that processing of emotion reasoning for self was earlier than that for others.The difference between the neural activity elicited by self-relevance processing and other-relevance processing in ToM provided the neuropsychological evidence to the simulation theory.The difference among time courses of the four kinds of mental state reasoning partially supported the theory theory of ToM.In addition,inhibiting demands loaded in mental states reasoning impacted the neural activity of online ToM processing,which provided evidence for the executive account.Taken together,the present thesis showed three conclusions.Firstly,neural activities elicited by mental states reasoning for different objects were associated with the late positive component,which might reflect various processes in To M such as the categorization of agents,the cognitive conflict and so on.Secondly,the divergence of neural activities elicited by mental states reasoning for different objects was located in frontal scalp areas.The neural substrate of ToM processing might be a broad network of brain regions including frontal cortex.Finally,existing theories of ToM might cannot account for the updated results appropriately.It is necessary to generate a new theoretical account that integrates overall evidences from experiments.