Neck motor unit activity displays neural signatures of temporal control during sequential saccade planning

Abstract

Goal-directed behavior involves the transformation of neural movement plans into appropriate muscle activity patterns. Studies involving single saccades have shown that a rapid, direct pathway links saccade planning in frontal eye fields (FEF) to neck muscle activity. It is unknown if the rapid connection between FEF and neck muscle is maintained during sequential saccade planning. We show that sequence planning signals in the FEF are preserved in the neck EMG, although the activity is delayed specifically for the second saccade. Our results suggest that while the direct link between FEF and neck muscle facilitates downstream continuation of FEF response patterns, an indirect route exists through an inhibitory control center like the basal ganglia, limiting the information flow during processing of saccade sequences. Thus, the indirect and direct pathways from the FEF may function together to enable rapid synchronous, but controlled eye-head responses to sequential gaze shifts.