A passive, camera-based head-tracking system for real-time, 3D estimate of head position and orientation in rodents
Tracking heads position and orientation of small mammals is crucial in many behavioral neurophysiology studies. Yet, full reconstruction of the heads pose in 3D is a challenging problem that typically requires implanting custom headsets made of multiple LEDs or inertial units. These assemblies need to be powered in order to operate, thus preventing wireless experiments, and, while suitable to study navigation in large arenas, their application is unpractical in the narrow operant boxes employed in perceptual studies. Here we propose an alternative approach, based on passively imaging a 3D-printed structure, painted with a pattern of black dots over a white background. We show that this method is highly precise and accurate and we demonstrate that, given its minimal weight and encumbrance, it can be used to study how rodents sample sensory stimuli during a perceptual discrimination task and how hippocampal place cells represent head position over extremely small spatial scales.