The Effect Of Oxytocin On Decision-making Behavior And Its Neural Basis

Oxytocin is a cyclic nine peptide molecule.On the one hand,it can act as a hormone in the peripheral nervous system,regulating uterine contractions,milk secretion,promoting childbirth and so on.On the other hand,it can also act as a neurotransmitter in the central nervous system,regulating a variety of social behaviors.The decision-making process can be divided into three parts: a trade-off between gains and losses of different choices,the evaluation of subjective values and to make the final choice.There were many psychological researches on oxytocin and decision-making,but these studies only focused on the relationship between oxytocin and social decision-making,such as trust game,ultimatum game,prisoner’s dilemma and so on.The studies in decision-making that does not involve interpersonal interaction is very few.Based on the previous studies,our research attempted to study the relationship between oxytocin and non-social decision-making behaviors.The effects of oxytocin on decision-making and the neural basis behind it were discussed through the following three studies.The first study focused on the behavioral aspects,examining the differences between the oxytocin group and the placebo group in the Iowa gambling task in behaviors.In the second study,we applied the pseudo-continuous arterial spin labeling technique which could record both ASL and BOLD signals in f MRI.We carried out f MRI scans of placebo group in the Iowa gambling task.By analyzing the similarities and differences in brain activation between the ASL and BOLD under the same scan sequence,we could find out if ASL is appropriated for f MRI in Iowa gambling task.The third study was also a f MRI study.The differences between oxytocin group and placebo group in brain activation in the Iowa gambling task were examined.In the first study,we recruited 34 healthy male volunteers from Southwest University.Firstly,in a double-blind design,we administered oxytocin nasal spray or a placebo to the 34 male college students.There were 16 students in the oxytocin group,and 18 students in the placebo group.Participants then completed the Raven’s standard progressive matrices in 40 minutes.Next,Participants needed to complete the Iowa gambling task in 15 minutes.The results showed that the oxytocin group was significantly performed better than the placebo group.Based on the Expectancy Valence Model,the oxytocin group had a bigger choice consistency than the placebo group.In the second study,18 students in the placebo group who had already completed the Raven standard progressive test were enrolled in the study.Firstly,scanning resting state.And then scanning the structure.Finally,we performed an MRI scan in the process of Iowa gambling task.By analyzing the similarities and differences between the two different signals(BOLD and ASL)in the same scan sequence,the results showed that ASL and BOLD had common brain activations in the decision-making stage.The same brain regions were regarded as mask and then we extracted the average activation intensity values of all the voxels in each mask.Next,making correlation analysis between the extracted data and the behavioral data.The results showed that there was a significant positive correlation between the activation of the left lateral occipital cortex/left parietal cortex and the Iowa gambling task scores in the fifth stage of the experiment.There was a significant negative correlation between the activation of the left putamen and the Iowa gambling task scores in the fifth/whole stage of the experiment.Further analysis showed that ASL activation intensity was lower than BOLD activation intensity.Therefore,BOLD is appropriated for f MRI scan in Iowa gambling task.Based on the results of study 2,the study 3 used the BOLD f MRI.In the third study,16 students in the oxytocin group who had already completed the Raven standard progressive test were enrolled in the study.The procedures were the same as study 2.The results showed that the activation of the postcentral gyrus,prefrontal cortex,cingulate gyrus,and superior parietal lobule in the oxytocin group were significantly greater than in the placebo group in the early stage of feedback.In the whole decision stage,the activation of precentral gyrus and postcentral gyrus in the oxytocin group were significantly greater than in the placebo group.In the whole feedback stage,the activation of the frontal lobe,superior parietal lobule,postcentral gyrus and paracingulate cortex in the oxytocin group were significantly greater than in the placebo group.There was no significant difference between the oxytocin group and placebo group in the early or late stage of decision making,and the late stage of feedback.Furthermore,the uncorrected results were analyzed.Z(Gaussianised T/F)statistic images were thresholded using clusters determined by Z>2.0 and P=0.05.After correction,four brain regions were found: right lingual gyrus,left prefrontal cortex,right prefrontal cortex,right precentral gyrus and postcentral gyrus.The four brain regions were regarded as mask and then we extracted the average activation intensity values of all the voxels in each mask.Next,making correlation analysis between the extracted data and the behavioral data.The results suggested that there was a significant positive/negtive correlation between the proportion of selecting cards CD/AB and brain activations in the prefrontal cortex,the right precentral gyrus and postcentral gyrus in the oxytocin group.There was no significant correlation in the placebo group.It could be inferred that the possible mechanism which can explain the better decision-making performance in the oxytocin group was that oxytocin increased the activation of the prefrontal cortex.In consideration of all the three studies and results above,it is concluded that oxytocin improves decision-making in the Iowa gambling task,through the increased activation of the prefrontal cortex.