Visual Simulation Is Supported by Sequential Monitoring in the Lateral Prefrontal Cortex

Visual simulation-a process that allows us to create complex internal models of the world-is essential for the completion of daily tasks, such as our morning commute. We can mentally track our progress along the route and make adjustments on the fly, all internally. Previous work has shown that complex visual simulations are supported by visuomotor regions across humans and nonhuman primates, but relatively little is known of the cognitive processes involved. We hypothesized that neural areas involved in sequential monitoring (i.e., keeping track of the state or step in an ordered series) are selectively active during visual simulation. A monotonic increase (ramping) in lateral prefrontal cortex (LPFC) activity has been previously shown to be necessary for executing nonmotor sequences. Therefore, to test the hypothesis, we examined LPFC activity in humans and a macaque monkey using fMRI while they performed a visual simulation task, "Planko." We found LPFC ramping across species that was specific to the visual simulation condition. These findings suggest that visual simulation tasks are supported by sequence monitoring regions across species, providing a foundation for understanding this complex and universal cognitive process.