Reciprocal Fronto-Parietal Interactions Support Motor Anticipation during Sequential Reaching

The transformation of sensory information into goal-directed motor plans and actions is known to emerge from coordinated activity between parietal and motor areas. Within this network, anticipation plays a critical role, enabling the brain to predict upcoming sensory inputs and prepare appropriate actions before sensory information becomes available. However, it remains unclear whether fronto-parietal interactions during motor anticipation follow a serial hierarchical organization or reflect distributed and reciprocal processing. To address this open question, we trained two rhesus macaques to perform a visually-guided sequential reaching task, in which the predictability of target location increased within the sequence. Analysis of eye and hand movements revealed that the degree of movement anticipation increased with target predictability. The direction of the upcoming reach toward predictable targets could be decoded from preparatory neural activity prior to target onset in both dorsal premotor-primary motor cortex (PMd/M1) and parietal area 7A. Using feature-specific information transfer analysis, we found that information about the upcoming movement direction was transmitted between 7A and PMd/M1 through bidirectional, yet asymmetric, interactions. Contrary to classical hierarchical models predicting serial activation across parietal and motor areas, parietal-to-motor interactions did not occur earlier than motor-to-parietal interactions. Instead, our findings support a heterarchical and reciprocal fronto-parietal network in which anticipatory processes adjust the timing of preparatory activity to facilitate eye-hand coordination during reaches to predictable targets.