Object detection through dynamic motor-sensory convergence in freely moving rats

To detect objects in natural environments, animals must coordinate movement and sensation. This process unfolds dynamically, as perceivers actively shape sensory input through ongoing motor actions in a closed loop. In this study, we use precise tracking of behavioral kinematics to investigate the initial phase of object interaction, asking: what motor-sensory strategies support object detection during natural approach? Using high-speed videography and advanced tracking tools, we tracked whisker and head dynamics as male rats approached and contacted objects. We found that whisker-object interactions converged toward a distinct ratio between changes in whisker angle and curvature, denoted α ^ . In a motor-sensory phase plane this ratio appears as a line, reflecting a regime in which small motor adjustments produce large curvature changes during contact. This motor-sensory ratio cannot stabilize during free-air whisking and thus can serve as a signature for object presence. Rats gradually converged toward this object-dependent mechanical signature across contacts, and proximity to α ^ predicted subsequent head movements and the termination of object approach. Convergence to α ^ was invariant to object shape and texture and to whisker’s length. Moreover, touch-induced pumps both signaled and reinforced convergence. The results suggest that rats use successful convergence to this object-dependent motor-sensory contingency as a signature of object presence. Object detection thus emerges as a closed-loop dynamical process in which action, mechanics, and sensation jointly shape perceptual inference. Significance Statement How does a rat know it is touching an object with its moving whiskers? We trained freely moving rats to discriminate objects while tracking whisker kinematics at high resolution. We found that the detection phase involved whisker-object interactions that converged toward a distinct ratio between changes in whisker angle and curvature. This ratio can arise mechanically only when whiskers contact an external object, making its attainment a reliable indication of object presence. During object approach, rats steered their exploratory movements to seek this motor-sensory contingency, marking the transition to focused exploration or disengagement. These findings reveal a dynamical, closed-loop mechanism for object detection in freely moving rats.