The Effects Of Oxytocin On Self–and Other-processing

Our ability to distinguish self from others is a fundamental aspect of human social behavior and has been studied extensively by cognitive neuroscientists and psychologists.In recent years the hypothalamic neuropeptide oxytocin has been shown to play an important role in many different aspects of human social behavior,however,few studies have examined its role in modulating the relationship between self and other processing.Previous studies have reported findings suggesting that intranasal oxytocin administration may influence self-processing by,for example,enhancing the ratings of extraversion and openness to experiences and increasing pain empathy when adopting the other perspective taking.In the current studies,we aimed to establish more fully the role of oxytocin in self and other processing using two established behavior paradigms involving self and other trait judgments and valuation of items owned by self and others.Neural effects of oxytocin were also investigated using functional magnetic resonance(fMRI)in conjunction with behavior.Self-and other-processing can become impaired in a number of psychiatric disorders such as autism,depression and schizophrenia and therefore the aim of the current studies was to establish whether oxytocin can help facilitate this important social function and therefore have potential therapeutic benefit?Self-referential effect is defined as the process by which a person becomes aware that specific contents are related to his or her own self and tends to remember self-relevant more than irrelevant information.Effects of intranasal oxytocin and self-referential behavior were investigated in the current task-dependent fMRI study using trait judgement task.In a double-blind placebo controlled within-subject experiment 41 male Chinese subjects randomly assigned to oxytocin and placebo treatment groups and tested individually.The experimental paradigm started 45 minutes after either intranasal oxytocin or placebo administration.In the scanner,subjects were required to judge whether the adjective word(positive or negative)was suitable for describing a trait exhibited by themselves,their mother,a classmate or a stranger.Subjects subsequently performed a “surprise” recognition memory test for the trait adjectives.Oxytocin reduced reaction times for making both self and other trait judgments indicating an improved speed of decision-making.Moreover,oxytocin also reduced subsequent bias for remembering self-attributed traits thereby indicating a reduction on self-orientated behavior.Neuroimaging data showed that this behavioral effect of oxytocin was associated with decreased dorsal medial prefrontal cortex(dmPFC)and ventral medial prefrontal cortex(vmPFC)responses.Oxytocin also decreased the functional connectivity between them and some other cortical midline regions(vmPFC—precuneus/PCC,dmPFC—ACC/hippocampus),which are important for self-vs.other processing.The effects of oxytocin on dmPFC,but not vmPFC,activation were positively associated with behavioral reaction time and self-esteem scores whereas the functional connectivity between dmPFC and anterior cingulate cortex was negatively associated with self-esteem.On the other hand,the vmPFC connectivity with posterior cingulate cortex was positively correlated with reaction times in the oxytocin treatment group,and oxytocin treatment abolished the positive correlation between the strength of this connectivity and self-esteem scores seen in the placebo group.Overall,both behavioral and neural findings in this study supported a role of oxytocin in blurring the differences between self and other thereby making individuals less self-orientated.Oxytocin effects on both behavioral and neural level were also modulated by levels of self-esteem.We always place greater value on items that we actually own and this is referred to as the endowment effect.Thus,the effects of oxytocin on the endowment effect were investigated in two separate experiments using a modified version of the Savings Hold or Purchase task,with the second study incorporating f MRI.In the two double-blind,between-subject placebo controlled experiments,male Chinese subjects(n = 35 and n = 41)were randomly assigned to oxytocin and placebo treatment groups.In the first behavioral study,subjects were asked to decide if they would buy or sell the product at the displayed price for themselves,for their mother,for their father or for a classmate.The procedure for fMRI experiment was similar except for small timing modifications to aid with the fMRI analysis and that a stranger ownership condition replaced the father ownership one as baseline.The behavioral results from the two independent experiments showed that oxytocin significantly enhanced the size of the endowment effect in individuals from a collectivist culture for both self-and all categories of other-(close: mother/ father and remote: classmate/ stranger)owned items.Neuroimaging results showed a differential pattern of oxytocin-evoked changes in the dmPFC and vmPFC(oxytocin decreased activation in the vmPFC for self-owned items but increased it for mother-owned ones and also increased it in the dm PFC for classmate and stranger-owned items).Activation in the dmPFC for self-and mother-owned items was associated with the size of the endowment effect as were differences in activation between self-and remote other-owned items.Additionally,oxytocin reduced the functional connectivity between the dmPFC and the ventral striatum in both self and mother-conditions,indicating a potential influence on reward processing.There was also reduced functional connectivity between the dmPFC and the precuneus in the self-ownership condition,further suggesting a reduced importance of self-owned items.There was no evidence for oxytocin having dose-dependent effects.In summary,we conducted two experiments using self-referential and endowment effect paradigms to investigate the effects of oxytocin on self-and other-processing.Both studies provided evidence that oxytocin can blur the distinction between self and other either by reducing the normal self-bias or by increasing the importance of others.These behavioral effects of oxytocin were associated primarily with altered activation of the medial prefrontal cortex and its connectivity with other regions in the default mode network implicated in self-and other-processing and the reward system.Thus,oxytocin may potentially have some therapeutic benefits for disorders where self-processing is dysfunctional.