Social monitoring of actions in the macaque frontopolar cortex

The role of frontopolar cortex in adjusting the balance between response execution and action inhibition in anthropoids

Executive control of behaviour entails keeping a fine balance between response execution and action inhibition. The most anterior part of the prefrontal cortex (frontopolar cortex) is highly developed in anthropoids; however, no previous study has examined its essential (indispensable) role in regulating the interplay between action execution and inhibition. In this cross-species study, we examine the performance of humans and macaque monkeys in the context of a stop-signal task and then assess the consequence of selective and bilateral damage to frontopolar cortex on monkeys' behaviour. Humans and monkeys showed significant within-session practice-related adjustments in both response execution (increase in response time (RT) and decrease in response variabilities) and action inhibition (enhanced inhibition). Furthermore, both species expressed context-dependent (post-error and post-stop) behavioral adjustments. In post-lesion testing, frontopolar-damaged monkeys had a longer RT and lower percentage of timeout trials, compared to their pre-lesion performance. The practice-related changes in mean RT and in RT variability were significantly heightened in frontopolar-damaged monkeys. They also showed attenuated post-error, but exaggerated post-stop, behavioural adjustments. Importantly, frontopolar damage had no significant effects on monkeys' inhibition ability. Our findings indicate that frontopolar cortex plays a critical role in allocation of control to response execution, but not action inhibition.

The big mixup: Neural representation during natural modes of primate visual behavior

The primate brain has evolved specialized visual capacities to navigate complex physical and social environments. Researchers studying cortical circuits underlying these capacities have traditionally favored the use of simplified tasks and brief stimulus presentations in order to isolate cognitive variables with tight experimental control. As a result, operational theories about visual brain function have come to emphasize feature detection, hierarchical stimulus encoding, top-down task modulation, and functional segregation in distinct cortical areas. Recently, however, experimental paradigms combining natural behavior with electrophysiological recordings have begun to offer a distinctly different portrait of how the brain takes in and analyzes its visual surroundings. The present article reviews recent work in this area, highlighting some of the more surprising findings in domains of social vision and spatial navigation along with shifts in thinking that have begun to emanate from this approach.

Simultaneous oscillatory encoding of "hot" and "cold" information during social interactions in the monkey medial prefrontal cortex

Social interactions in primates require social cognition abilities such as anticipating the partner's future choices as well as pure cognitive skills involving processing task-relevant information. The medial prefrontal cortex (mPFC) has been implicated in these cognitive processes. Here, we investigated the neural oscillations underlying the complex social behaviors involving the interplay of social roles (Actor vs. Observer) and interaction types (whether working with a "Good" or "Bad" partner). We found opposite power modulations of the beta and gamma bands by social roles, indicating dedicated processing for task-related information. Concurrently, the interaction type was conveyed by lower frequencies, which are commonly associated with neural circuits linked to performance and reward monitoring. Thus, the mPFC exhibits parallel coding of both "cold" processes (purely cognitive) and "hot" processes (reward and social-related). This allocation of neural resources gives the mPFC a key neural node, flexibly integrating multiple sources of information during social interactions.

Neurons in the monkey frontopolar cortex encode learning stage and goal during a fast learning task

The frontopolar cortex (FPC) is, to date, one of the least understood regions of the prefrontal cortex. The current understanding of its function suggests that it plays a role in the control of exploratory behaviors by coordinating the activities of other prefrontal cortex areas involved in decision-making and exploiting actions based on their outcomes. Based on this hypothesis, FPC would drive fast-learning processes through a valuation of the different alternatives. In our study, we used a modified version of a well-known paradigm, the object-in-place (OIP) task, to test this hypothesis in electrophysiology. This paradigm is designed to maximize learning, enabling monkeys to learn in one trial, which is an ability specifically impaired after a lesion of the FPC. We showed that FPC neurons presented an extremely specific pattern of activity by representing the learning stage, exploration versus exploitation, and the goal of the action. However, our results do not support the hypothesis that neurons in the frontal pole compute an evaluation of different alternatives. Indeed, the position of the chosen target was strongly encoded at its acquisition, but the position of the unchosen target was not. Once learned, this representation was also found at the problem presentation, suggesting a monitoring activity of the synthetic goal preceding its acquisition. Our results highlight important features of FPC neurons in fast-learning processes without confirming their role in the disengagement of cognitive control from the current goals.

The transitive inference task to study the neuronal correlates of memory-driven decision making: A monkey neurophysiology perspective

A vast amount of literature agrees that rank-ordered information as A>B>C>D>E>F is mentally represented in spatially organized schemas after learning. This organization significantly influences the process of decision-making, using the acquired premises, i.e. deciding if B is higher than D is equivalent to comparing their position in this space. The implementation of non-verbal versions of the transitive inference task has provided the basis for ascertaining that different animal species explore a mental space when deciding among hierarchically organized memories. In the present work, we reviewed several studies of transitive inference that highlighted this ability in animals and, consequently, the animal models developed to study the underlying cognitive processes and the main neural structures supporting this ability. Further, we present the literature investigating which are the underlying neuronal mechanisms. Then we discuss how non-human primates represent an excellent model for future studies, providing ideal resources for better understanding the neuronal correlates of decision-making through transitive inference tasks.