Summary: New research shows the spinal cord has intrinsic learning and memory capabilities, overturning the notion that it only relays messages between brain and body. Using an innovative behavioral setup, researchers identified two distinct inhibitory neuronal populations in the spinal cord that enable independent acquisition and recall of motor adaptations.
These findings refine our understanding of spinal cord plasticity and suggest promising avenues for rehabilitation after spinal injuries. By revealing how spinal circuits encode and store movement-related information, the study points to new strategies for enhancing motor recovery following trauma.
Key Facts:
- The spinal cord can autonomously learn and retain motor adaptations via distinct dorsal and ventral inhibitory neurons.
- A novel experimental paradigm measuring rapid movement changes in awake, behaving mice enabled identification of these cell-type specific roles.
- The discoveries have potential implications for spinal injury rehabilitation, offering new targets for therapies that promote recovery and motor relearning.
Source: VIB
Rethinking the spinal cord: more than a relay
Traditionally considered a passive conduit between brain and body, the spinal cord is now shown to possess its own capacity for learning and memory related to movement. A research team at Neuro-Electronics Research Flanders (NERF), led by Professor Aya Takeoka, demonstrates that spinal circuits can both acquire and later recall motor adaptations without ongoing brain involvement.
Published in Science, the study provides a detailed account of how spinal inhibitory neurons support the learning and automation of movement. The results shed light on the spinal cord’s internal mechanisms of plasticity and suggest how these mechanisms might be harnessed to aid rehabilitation in people with spinal cord or brain injuries.
The spinal cord’s puzzling plasticity
The spinal cord integrates diverse sensory inputs to modulate and fine-tune actions and reflexes. Importantly, it can perform these functions independently of brain input. Over repeated practice, spinal neurons can change their responses and improve performance on specific tasks—a form of local learning. Until now, identifying which neurons perform these roles and how they encode learned behaviors was a major challenge.
Professor Takeoka’s lab focuses on how spinal circuits rewire and adapt during recovery from injury. One technical hurdle has been recording single-neuron activity in the spinal cord of awake, moving animals. To overcome this, the team developed a behavioral model that induces rapid, measurable motor learning within minutes, enabling precise cell-type analysis of spinal plasticity.
Two specific neuronal cell types
Doctoral researcher Simon Lavaud and colleagues adapted approaches from insect neurobiology to build an experimental platform that quantifies small changes in limb movements in mice. Using this system, the team tested six neuronal populations and found that two inhibitory cell classes play complementary roles in spinal motor learning.
Dorsal inhibitory neurons were required for acquiring a new motor adaptation. These cells shape the flow of somatosensory information, boosting the salience of conditioning cues linked to limb position and enabling the spinal cord to adjust behavior. In contrast, ventral inhibitory neurons—identified as Renshaw cells—were essential for maintaining and flexibly recalling the learned motor response.
As Lavaud explains, the dorsal and ventral populations act in sequence: dorsal neurons support the initial learning phase by routing sensory signals that mark relevant changes, while ventral neurons later support stable expression and recall of the adapted movement, ensuring smooth execution.
Learning and memory outside the brain
The study’s electrophysiological and behavioral data demonstrate that spinal neuronal activity mirrors classical signatures of learning and memory, including acquisition and retention. Understanding these mechanisms in greater detail will be essential for translating basic discoveries into clinical strategies that leverage spinal plasticity for rehabilitation.
According to Prof. Takeoka, the circuit architecture described in this work offers a mechanism by which the spinal cord contributes to both motor learning and long-term motor memory. These spinal processes likely support everyday motor control in healthy individuals and may be particularly important during recovery from brain or spinal cord injury.
Funding: The research team received support from the Research Foundation Flanders (FWO), Marie Skłodowska-Curie Actions (MSCA), a Taiwan–KU Leuven PhD fellowship (P1040), and the Wings for Life Spinal Cord Research Foundation.
About this learning and memory research news
Author: India Jane Wise
Source: VIB
Contact: India Jane Wise – VIB
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Two inhibitory neuronal classes govern acquisition and recall of spinal sensorimotor adaptation” by Aya Takeoka et al., published in Science.
Abstract
Two inhibitory neuronal classes govern acquisition and recall of spinal sensorimotor adaptation
Spinal circuits are central to movement adaptation, yet the mechanisms within the spinal cord responsible for acquiring and retaining behavior upon experience remain unclear. Using a simple conditioning paradigm, the authors found that dorsal inhibitory neurons are indispensable for adapting protective limb-withdrawal behavior by regulating transmission of a specific set of somatosensory signals, thereby enhancing the saliency of conditioning cues associated with limb position.
By contrast, maintaining previously acquired motor adaptation required ventral inhibitory Renshaw cells. Manipulating Renshaw cells did not disrupt the acquisition of adaptation but did alter the expression and flexibility of the adaptive behavior.
These results identify a circuit basis—two distinct populations of spinal inhibitory neurons—that enables lasting sensorimotor adaptation independently from the brain.