Single-unit (SU) activity - action potentials isolated from one neuron - has traditionally been employed to relate neuronal activity to behavior. However, recent investigations have shown that multi-unit (MU) activity - ensemble neural activity recorded within the vicinity of one microelectrode - may also contain accurate estimations of task-related neural population dynamics. Here, using an established model-fitting approach, we compared the spatial codes of SU response fields with corresponding MU response fields recorded from the frontal eye fields (FEF) in head-unrestrained monkeys (Macaca mulatta) during a memory-guided saccade task. Overall, both SU and MU populations showed a simple visuomotor transformation: the visual response coded target-in-eye coordinates, transitioning progressively during the delay toward a future gaze-in-eye code in the saccade motor response. However, the SU population showed additional secondary codes, including a predictive gaze code in the visual response and retention of a target code in the motor response. Further, when SUs were separated into regular / fast spiking neurons, these cell types showed different spatial code progressions during the late delay period, only converging toward gaze coding during the final saccade motor response. Finally, reconstructing MU populations (by summing SU data within the same sites) failed to replicate either the SU or MU pattern. These results confirm the theoretical and practical potential of MU activity recordings as a biomarker for fundamental sensorimotor transformations (e.g., Target-to-Gaze coding in the oculomotor system), while also highlighting the importance of SU activity for coding more subtle (e.g., predictive / memory) aspects of sensorimotor behavior.Significance statement Multi-unit recordings (undifferentiated signals from several neurons) are relatively easy to record and provide a simplified estimate of neural dynamics, but it is not clear which single-unit signals are retained, amplified, or lost. Here, we compared single- / multi-unit activity from a well-defined structure (the frontal eye fields) and behavior (memory-delay saccade task), tracking their spatial codes through time. The progressive transformation from target-to-gaze coding observed in single-unit activity was retained in multi-unit activity, but other cognitive signals (gaze prediction within the initial visual response, target memory within the final motor response, and cell-specific delay signals) were lost. This suggests that multi-unit activity provides an excellent biomarker for healthy sensorimotor transformations, at the cost of missing more subtle cognitive signals.