The Cognitive And Neural Mechanisms Of Intertemporal Choice In Gain And Loss Conditions

Intertemporal choice refers to the process of balancing the benefits and losses at different time points in the future(Frederick, Loewenstein, & O’donoghue, 2002).Intertemporal choice is very common in daily life, e.g. in education, working,marriage, and even in national environmental protection, sustainable development strategy, etc.. Therefore, the research on the intertemporal choice can benefit people on making more rational choices. In recent years, with the development of economics,psychology and cognitive neuroscience, the study of behavioral and neural mechanism of intertemporal choice have become a hotspot in the field of decision making.Obviously the intertemporal choice is not only occurred in the benefit situation but also occurred in the loss situation. Previous studies demonstrate that two kinds of situations’ time discount differ remarkably. People always discount delayed losses more subtly than delayed gains(read, 2004; Thaler, 1981). However, recent behavior researches of intertemporal choice concentrated in the gain conditon, while neural mechanism in loss situation is little known. It is still ambiguous that whether time discounting in gains and losses share a common behavior and neural mechanism. Hence more researches on intertemporal choice in both gain and loss conditions are valuable to acquire better understanding of the behavior and neural mechanism on itertemporal choice(Bickel,Pitcock, Yi, & Angtuaco, 2009; Xu, Liang, Wang, Li, & Jiang, 2009; Yi, Mitchell,Bickel &, 2010). Therefore, studies in gain and loss situations should be conducted.Considering the basis of previous studies, this research examined the behavior and neural mechanism of intertemporal choice in gain and loss condition, in a behaviormethod and a fMRI method with two decision making task. The behavior measurement employed a classical titration method of intertemporal choice and the fMRI data adopted voxel-based morphometry technology to analysis. Through the two studies,the behavior and neural mechanism of the two different conditions in intertemporal choice is well investigated deeply. Specifically, the first study adopted behavior experiment to investigate the behavior mechanism of intertemporal choice in gain and loss conditions by using titration method, the second study employed the behavior experiment and the magnetic resonance experiment to investigate the neural mechanism of intertemporal choice in gain and loss conditions by using titration method and magnetic resonance technique. Through the behavior and magnetic resonance experiment, it is suggested to find out the similarities and differences between the two different situations. Finally it is hypothesized that the discounting of the gain and loss condition in future may share some common behavior and neural mechanism. Additionally the behavior and neural mechanism might be asymmetric in intertemporal choice of gain and loss condition.In the first study we used behavior experiment to investigate the behavior mechanism of intertemporal choice in gain and loss conditions by using titration method, Forty-six college students(18male and 28 female) participated the experiment.Results illustrated that:(1) The time discounting model was well fitted with the hyperbolic curve both in gain and loss condition.(2) The time discounting in gain and loss conditions was significantly positively correlated.(3)The asymmetric in time discounting between loss and gain conditions demonstrated the discount curves in loss condition was less steeply, which result was same with previous studies. Hence it is suggested that the time discounting in two conditions shares the same discount trend,but people weigh the time discounting in gain condition more than in the loss situation.In the second study, behavior experiment and magnetic resonance experiment were adopted to investigate the neural mechanism of intertemporal choice in gain and loss conditions by using titration method and magnetic resonance technique. The fMRI data were collected in voxel morphology method to explore the neural basis of different situations’ time discounting in intertemporal choice. Forty-six college student(18male and 28 female) participated the experiment. Results showed that:(1) The grey matter of posterior cingulate(PCC), left anterior cingulate cortex(ACC), bilateral cingulate(MCC), left parahippocampal gyrus(parahippocampal), medial orbitofrontal cortex(mOFC) were negatively linked to time discounting in gain condition. but therewere no regions in which time discounting displayed a positive relationship with regional grey matter volume.(2) The grey matter of the left anterior cingulate in loss situation(ACC), bilateral cingulate(MCC), bilateral insula displayed a negative link to time discounting in loss condition and there were no regions in which time discounting displayed a positive relationship with regional grey matter volume.(3) The grey matter of the left anterior cingulate(ACC) and left cingulate(MCC) were negatively linked to time discounting in both gain and loss conditions by using combined comparative analysis. These result suggested that people discounted future result might share a same neural mechanism both in gain and loss condition.Our study provided some evidence to explore behavior and neural mechanism both in gain and loss situations:(1)Time discounting model can be fitted well with hyperbolic curve both in the gain and loss conditions. Time discounting in the gain and loss condition was significantly positively correlated and we also found the asymmetric in time discounting between the loss and gain conditions, where the discount curves showed that loss was less steeply.(2) The grey matter of posterior cingulate(PCC), left anterior cingulate cortex(ACC), bilateral cingulate(MCC), left parahippocampal gyrus(parahippocampal), medial orbitofrontal cortex(mOFC)were negatively linked to time discounting in the gain condition. but there were no regions in which time discounting displayed a positive relationship with the regional grey matter volume.The grey matter of the left anterior cingulate in loss situation(ACC),bilateral cingulate(MCC), bilateral insula displayed negatively linked to time discounting in loss condition and there were no regions in which time discounting displayed a positive relationship with regional grey matter volume. The grey matter of the left anterior cingulate(ACC) and left cingulate(MCC) were negatively linked to time discounting in both gain and loss condition by using combined comparative analysis. This research demonstrated that people evaluating future discounted both in the gain and loss situations were affected by some cognitive control brain regions. And the neural bases of the gain and loss conditions were not completely symmetrical.People discount future loss less steeply, which might be effected by the insula.