Stimulus And Reward Information Encoded By Population Neurons In The Primate Prefrontal Cortex And Striatum

The prefrontal cortex and striatum are closely connected through direct or indirect pathways,which are two major areas in the brain.Many studies have reported that these two brain areas have similar advanced cognitive functions,such as:participation in motion control,value calculation,behavioral decision-making,learning and memory,and reward information processing.Furthermore,neurons in the prefrontal cortex encode a set of stimuli(a set)in relation to rewards,whereas striatum neurons encode a specific stimulus-to-reward relationship.The prefrontal cortex is involved in value calculation of model-based learning,while striatum is involved in value calculation of model-free learning.However,these results are mostly based on the study of the firing activity of individual neuron,and little consideration has been given to whether population neurons in the two brain areas can reliably represent task-related information.To further study this issure,we recorded single-unit activities in the lateral PFC(LPFC)and striatum while the monkey was performing a stimulus-reward prediction task,and analyzed neuronal activities by the method of a multi-variable regression model and the linear vector support machine.It was found that although proportions of task-related neurons in the two areas varied largely in the whole trial period,LPFC population neurons encoded reward and stimulus information stably and reliably.Population neurons in the striatum encoded only reward information,not stimulus information.Neurons in both areas encode a combination of stimulus and reward,and there is no significant difference in the proportion of nonlinear mixed-selective neurons in the two brain regions.The results of this paper indicate that prefrontal cortex and striatum population neurons have similar heterogeneity and both can stably represent task-related parameters,but the information they encode is different,corresponding to their different roles in value decision-making.