Efficiency and robustness in three cortical areas: frontal pole cortex, dorsolateral prefrontal cortex and orbitofrontal cortex.

The prefrontal cortex in primates has a diverse evolutionary history, characterized by distinct phases of development. Granular regions of the orbital prefrontal cortex (PFo) emerged early in primate evolution, while other granular areas, such as the dorsolateral (PFdl) and polar (PFp) regions, evolved later during anthropoid development. This study explored the functional differences among PFp, PFdl, and PFo in macaque monkeys, focusing on their coding mechanisms, specifically regarding robustness and efficiency. Efficiency was estimated using the 'contrast entropy', defined as the entropy of the neuronal spiking activity normalized by the expected theoretical maximum, whereas robustness was estimated as the synchrony of activity between neurons within the same area. Our investigation revealed that PFp and PFdl show superior information capacity, reflecting efficient coding compared to PFo. Conversely, PFo exhibited higher robustness, suggesting a trade-off relationship between efficiency and robustness consistent with distinct evolutionary stages. The newly incorporated granular prefrontal cortex regions, namely PFp and PFdl, appear to employ a more highly efficient neural code at the expense of reliability, as evidenced by lower robustness.