Role of rodent secondary motor cortex in value-based action selection

Abstract

Despite widespread neural activity related to reward values, signals related to upcoming choice have not been clearly identified in the rodent brain. Here, we examined neuronal activity in the lateral (AGl) and medial (AGm) agranular cortex, corresponding to the primary and secondary motor cortex, respectively, in rats performing a dynamic foraging task. Choice signals arose in the AGm before behavioral manifestation of the animal’s choice earlier than in any other areas of the rat brain previously studied under free-choice conditions. The AGm also conveyed significant neural signals for decision value and chosen value. In contrast, upcoming choice signals arose later and value signals were weaker in the AGl. We also found that AGm lesions made the animal’s choices less dependent on dynamically updated values. These results suggest that rodent secondary motor cortex might be uniquely involved in both representing and reading out value signals for flexible action selection.

Hippocampal Neural Correlates for Values of Experienced Events

“…Moreover, value signals were regionally specific (largely absent in the subiculum) and robust, as confirmed by the analyses in both spatial and temporal domains, by using different methods to define place fields and also by controlling for the effects of potential confounding behavioral variables, making it unlikely that they merely reflected spurious correlation of neural activity with some other variables. Finally, strengths of action value and chosen value signals found in CA1 were comparable to those found in other brain structures well known to be involved in value processing (striatum and frontal cortex) Sul et al, 2010Sul et al, , 2011. These results provide converging evidence for significant value signals in CA1.…”

“…We showed previously that neural signals for chosen value and choice outcome are combined differently across neurons in various regions of the corticobasal ganglia loop to compute RPE or update chosen value immediately (within ϳ1 s) after the choice outcome was revealed Sul et al, 2010Sul et al, , 2011. These results provided evidence for active involvement of multiple brain structures in the evaluation of choice outcomes in reference to previous experiences.…”

“…Previous studies in the frontal cortex and striatum have shown that these three types of neural signals temporally overlap immediately (within ϳ1 s) after the outcome of the animal's goal choice is revealed Sul et al, 2010Sul et al, , 2011. We Table 2.…”

“…In the present study, to resolve this matter, we recorded hippocampal neuronal activity in rats performing a dynamic foraging task. During this task, expected reward values varied dynamically across trials according to the history of the animal's choices and their outcomes, so that neural activity reflecting expected reward values can be separated from the activity that merely registers the receipt of reward Sul et al, 2010Sul et al, , 2011.…”

Cortical neural responses to previous trial outcome during learning of a directional choice task

“…In addition to its neurons involved in predicting trial outcomes, lesions of AGm cause an increase in reaction time, which suggests an involvement in movement preparation (Smith et al 2010). Additionally, AGm neurons encode the action selected before movement onset in a valuebased directional choice task (Sul et al 2011).…”