The Cognitive And Neural Mechanism Of The Effect Of Multi-scale Temporal Cognition On Intertemporal Choice

Intertemporal choice refers that decision makers tradeoff the costs and benefits of outcomes which occur at different times(Frederick et al.,2002).An important finding regarding intertemporal choice is delay discounting also called time discounting,which refers the process of devaluing the outcomes that take place in the future.Neuroimaging studies have showed that delay discounting involves three brain networks: valuation network,cognitive control network,and prospective network(Peters & Büchel,2011).However,most of the previous researchers built the theoretical model of intertemporal choice from the perspective of value,and viewed the delayed time as an objective variable.They emphasized that using the theoretical models to reveal how the value of rewards varies with the objective delayed time.Dealing with time is a fundamental characteristic of human experience,both objective,so-called clock time,and subjective,psychological construction of time.However,many previous studies have neglected the individual differences in subjective time.Kim and Zauberman(2009)proposed the "perceived-time-based model of temporal discounting",which emphasized the importance role of subjective time perception in intertemporal choice.Although some research have showed that this model could explain many effects in intertemporal choice(such as sign effect,date/delay effect),most of these studies are in the stage of model exploration and lack of experimental evidence,even lack of the neuroimaging evidence.There are different scales for human temporal cognitive,from a large scale temporal cognitive for time frame(the past,present,and future frame)to a minor scale temporal cognitive for short-term time perception(Buhusi & Meck,2005).Huang et al.,(2003)proposed the Range-synthetic Model of Temporal Cognition,which emphasized different scales for temporal cognition have different mechanisms and are influenced by many factors.Therefore,whether the multi-scale temporal cognition will have the same effect on intertemporal choice,what are the neural mechanisms for these effects,these questions are still unclear.Currently,the study of intertemporal choice mainly involves the trade-off between immediate benefits(or losses)and future benefits(or losses).This involves,first of all,individual's perception of the large-scale time frames,which refers the time perspective.The delayed time in intertemporal choice is usually a large future time duration.This relatively large-scale time perception involves the anticipatory perception of future time.Some studies have shown that time perception in the short-term range is associated with impulsivity(Wittmann & Paulus,2008).Intertemporal choice is an important indicator of the impulsivity.This paper examined the behavioural and neural prediction of short-term time perception on intertemporal choice.Systematically exploring the effects of multi-scale temporal cognition on intertemporal choice and their neural basis not only can reveal the cognitive and neural mechanism of intertemporal choice from the perspective of subjective time,but also help to improve the "perceived-time-based model of temporal discounting" proposed by Kim and Zauberman(2009).Based on previous studies,this paper systematically explored the influence of three scales of temporal cognition(time frame,anticipatory perception of future time,and short-term time perception)on intertemporal choice using behavioral tests and multi-modal MRI technology from the perspective of temporal cognition.In our first study,we adopted behavior experiment and voxel-based morphometry(VBM)methods to investigate the effect of time perspective(TP)on intertemporal choice.We found that(1)only Future TP was a significant predictor of DD,and higher scores on Future TP were related to lower discounting rates;(2)steeper discounting correlated with greater GM volume in the ventromedial prefrontal cortex(vm PFC)and ventral part of posterior cingulate cortex(v PCC);Also,GM volume of a cluster in the vm PFC was correlated with Future TP.Interestingly,there was an overlapping region in vm PFC that was correlated with both DD and Future TP;(3)the overlapping region of vm PFC played a partially mediating role in the relation between Future TP and DD in the other independent dataset.These results suggest that vm PFC may be the neural basis of the effect of Future TP on intertemporal choice.On the basis of Study 1,Study 2 further examined the effect of anticipatory future time perception on intertemporal choice.Study 2,which investigated the effect of anticipatory perception of future time on intertemporal choice and its neural basis,included 3 experiments.In the first experiment,we adopted the perception anticipatory future time task and delay discounting task,and found that(1)individuals' subjective perception of anticipatory future duration are not sufficiently sensitive to changes in objective duration;(2)when the subjective future time is used instead of the objective future time,the discounting rates at each time point remain stable.(3)the variation of reward value with the subjective perception of the future time can be better fit using the exponential function compared with the hyperbolic function.Previous studies have shown that the hyperbolic discounting model can well fit how the value of reward varies with the objective delayed time.Thus,for each subject,we used the hyperbolic function and exponential function to fit the objection time discounting and the subjective time discounting,respectively,indicating that the devalued degree of the reward value with the objective delayed time and the subjective perception delayed time increase.In the second experiment of Study 2,we explored the neural basis of the objective time discounting and the subjective time discounting using the large-scale brain network analyses.We found that(1)objective time discounting were positively correlated with the functional network connectivity(FNC)between cingulo-opercular network(CON)and default mode network(DMN),while were negatively related to the FNC of both CON-SAN(salience network)and SAN-FPN(fronto-parietal network);(2)the subjective time discounting only negatively correlated with FNC of CON-SAN.These results suggest that the FNC between the brain's cognitive control related networks and the connection with the value representation network can predict the objective time discounting,and only the FNC between cognitive control networks can predict the subjective time discounting.Intertemporal choice are influenced by many state factors,and the episodic prospection is one of the most important state factor(Peters & Büchel,2010).Some studies have also shown that the prospective emotion induced by episodic prospection can affect the human's time perception.In the third experiment of the Study 2,we mainly examines the psychological mechanism of the effect of episodic prospection on intertemporal choice from the perspective of subjective perception of the anticipatory future time.Study 3 used the pre-and-post-test design and manipulated the sign of the episodic prospection(positive and negative)and the constructive level(low and high construct).Our results shown that the low-level construct for positive episodic prospection reduced the participants' subjectively estimated length of future time,while the low-level construct for negative episodic prospection increased the participants' subjectively estimated length of future time;regardless of positive or negative events,the high-level construct for episodic prospection did not change the participants' subjective perception of future duration;the low-level construct for positive episodic prospection reduced the participants' objective time discounting rates while the low-level construct for negative episodic prospection increased the objective time discounting rates,but has no effect on the subjective time discounting.These results suggest that low-level construct for positive or negative events will change the participants' subjectively perceptive future duration,while also changed the objective time discounting,but not changed the subjective time discounting.Therefore,the changes of the subjectively perceptive future duration may be the psychological mechanism underling the effect of episodic prospection on intertemporal choice.Study 3 used behavioral and task-state fMRI technique to examine the predictive role of short-term time perception on intertemporal choice and the corresponding neural basis for this prediction.We found that(1)participant's produced time in the time productive task was negatively correlated with delay discounting,that is,the faster the internal clock rate,the steeper the delay discounting is;(2)that the activity of the lateral prefrontal cortex(LPFC)when participants complete the time productive task can significantly predict the delay discounting rates,and the stronger the activity in LPFC,the lower the discounting rates.These results suggest that the short-term time perception can predict delay discounting,and the LPFC may be the neural mechanism underling this predictive effect of time perception on intertemporal choice.Taken together,we found that(1)Future TP can significantly predict delay discounting,and the vm PFC that involves in value representation is the neural basis for the effect of Future TP on intertemporal choice.(2)individuals' subjective perception of anticipatory future duration are not sufficiently sensitive to changes in objective duration,and the variation of reward value with the subjective perception of the future time can be better fit using the exponential function compared with the hyperbolic function.(3)The FNC between the brain's cognitive control related networks and the connection with the value representation network can predict the objective time discounting,and only the FNC between cognitive control networks can predict the subjective time discounting.(4)Participants perceived the changes of the future duration may be the psychological mechanism underling the effect of episodic prospection on intertemporal choice.(5)Delay discounting can be predicted by the short-term time perception can predict delay discounting.The activities of LPFC be the neural mechanism underlying the association between short-term time perception and delay discounting.Our results suggest that the three scale for temporal cognition have influence on the intertemporal choice,but the mechanism underlying the influence is different.Relatively large-scale temporal cognition(including time frame and anticipatory future time perception)may have an impact on the process of value representation,while small-scale temporal cognition may have an impact on the process of cognitive control in intertemporal choice.Our findings may have important theoretical value for improving the perceived-time-based model of temporal discounting,and have also practical value for the intervention of intertemporal choice.Future researchers could adopt different scales temporal cognition to intervene the value representation or cognitive control processes in intertemporal choice.