A NOVEL APPROACH FOR INVESTIGATING SENSORY ENCODING IN THE DORSAL SPINAL CORD OF FREELY MOVING MICE

The spinal cord is a key relay between the peripheral nervous system and the brain, playing a central role in somatosensory information processing. Within the spinal grey matter, complex neuronal networks integrate incoming signals from brain, skin and internal organs, while their organization and function remain poorly understood. Stable and long-term recordings of these networks in vivo, particularly in freely behaving rodents, remain extremely challenging. Classical approaches in anesthetized animals suppress movements but restrict investigations to sensory inputs, while recent approaches suitable for awake recordings often rely on heavy and unwieldy devices disrupting natural posture and locomotion. Here, we present a novel electrode system designed for bilateral spinal recordings in freely moving rodents, allowing chronic monitoring of neural activity while preserving natural behavior. Focusing on dorsal horn electrophysiological recordings, we show that spinal cord activity correlates with spontaneous animal movements. We identify mechanically sensitive, thermosensitive, and polymodal units exhibiting distinct coding properties. Spike waveform analysis further reveals associations between electrophysiological features and specific neuronal subpopulations, providing insights into the functional organization of dorsal horn. Finally, we demonstrate that contralateral spinal cord encodes sensory information from the opposite body part. Together, these findings reveal the dynamics of the dorsal spinal cord, and our device enables in-depth, powerful analysis of neuronal activity associated with specific sensory stimulations, opening new perspectives for understanding spinal sensory processing in naïve and pathological conditions.