Motor cortical dynamics are shaped by multiple distinct subspaces during naturalistic behavior

Behavior relies on continuous influx of sensory information about the body. In primates, motor cortex must integrate somatic feedback to accurately reach and manipulate objects. Yet, prior work demonstrates that motor cortex is well-described with deterministic, rather than input-driven, dynamics. Deterministic dynamics facilitate robust movement generation, but flexible motor output requires rapid responses to unexpected inputs. Here, we resolved this paradox by simultaneously recording neural population activity in motor and somatosensory cortex from four monkeys performing a naturalistic object interaction behavior resulting in occasional errors. Motor cortex was strikingly input-driven surrounding behavioral error correction. Intriguingly, input-driven dynamics were isolated to a subspace of the population activity that putatively captured somatosensory feedback. Using electrical stimulation of ascending somatosensory tracts, we causally verified that this feedback subspace captured peripheral inputs to cortex. Our results demonstrate that cortical activity is compartmentalized within distinct subspaces, enabling flexible integration of salient inputs for robust behavior.