Coordinated parieto-frontal neuronal communication is critical for abstract quantity judgments in primates

Accurate numerical cognition relies on representing and comparing quantities, a fundamental skill for adaptive behavior. In nonhuman primates, the parieto-frontal network, including the ventral intraparietal area (VIP) and prefrontal cortex (PFC), supports this process, but the functional dynamics and directionality of communication between these regions remain unclear. We examine population-level interactions of simultaneously recorded neuronal activity between VIP and PFC in two male macaques performing a numerosity task. Using time-lagged canonical correlation analyses, we show that correct trials exhibit sustained correlations driven by numerosity-selective neurons, with early feedforward dominance from VIP to PFC following sample onset. By contrast, error trials show weaker correlations, reduced VIP-to-PFC feedforward signaling, and transient breakdowns during the late working memory period. These findings show that coordinated parieto-frontal population activity enables accurate numerical judgments, whereas disrupted interactions impair performance, highlighting the critical role of dynamic, task-dependent interareal communication in categorical decisions.