A systems approach to orbitofrontal cortex function: recordings in rat orbitofrontal cortex reveal interactions with different learning systems.

The recognition that certain aspects of prefrontal function can be effectively modeled in rats has led to a slow expansion of interest in rat prefrontal cortex over the past decade. One of the most promising of these model systems is the orbitofrontal cortex of the rat. Rat orbitofrontal cortex is anatomically similar to the orbital prefrontal region in primates, and this similarity is borne out by behavioral and neurophysiological findings. Here we will present data on orbitofrontal cortex function from a number of parallel studies from our laboratories that employed single unit recording techniques to probe neural encoding in rat orbitofrontal cortex and related parts of the amygdala and the hippocampal memory systems. Together, these reports and associated behavioral studies suggest that the orbitofrontal region, in both rats and primates, is specialized to integrate concrete and abstract sensory constructs with information regarding the incentive value of associated outcomes to guide or modulate behavior. To the extent that monkey prefrontal function can model certain aspects of human prefrontal function, we argue that this model can now be extended to the rat orbitofrontal cortex. In addition, we argue that the function of orbitofrontal cortex needs to be considered in terms of its interactions with other brain systems.