Neural correlates of trial outcome monitoring during long-term learning in primate posterior parietal cortex

Monitoring behavioral outcomes is essential for optimizing behavior and learning new tasks. However, how the brain monitors outcome information during long-term learning remains largely unknown. Using two-photon calcium imaging in behaving monkeys, we tracked neuronal activity in area 7a of the posterior parietal cortex (PPC), an important associative cortex that has not been typically implicated in associative learning (AL), while the macaque monkeys learned new visuomotor associations across multiple days. We found robust neuronal representation of salient behavioral outcomes (correct vs. incorrect) which closely correlated with the monkeys' learning behavior. Furthermore, these outcome representations significantly reorganized when monkeys transitioned to learn novel associations and gradually evolved over subsequent learning days, a process constrained by the functional connectivity among neurons within local network. These results suggest a substantive role for primate PPC in long-term AL through monitoring trial outcome, and indicate a principle for long-term learning: network connectivity constrains the evolution of neural encodings.