Sign in

Robin Rohlén

@robinrohlen.bsky.social
10 followers 43 following 13 posts
PostsRepliesMedia
Reposted by Robin Rohlén
bioRxiv Neuroscience @biorxiv-neursci.bsky.social · 05/08/2026
An axonal sodium current gates motoneuron doublets and force amplification www.biorxiv.org/content/10.64898/20…
021
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
This is joint work with David Bennett, Monica Gorassini, and Dario Farina. Preprint and full details: www.biorxiv.org/content/10.6.... Feedback very welcome. (12/12)
biorxiv.org
An axonal sodium current gates motoneuron doublets and force amplification
Brief high-frequency bursts of action potentials shape neural coding. In spinal motoneurons, they appear as doublets, closely spaced spike pairs observed for a century that amplify muscle force nonlin...
000
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
The takeaway: the axon is not just a passive cable that relays somatic spikes. The NaP current actively shapes output timing, producing doublets that recur across rats, mice, and macaques and across slow and fast natural tasks. (11/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
In humans, motor units fired repetitive doublets during voluntary contraction with the doublet-frequency adaptation. The NaP currents behind doublets are dysregulated in ALS and targeted by its treatments, making doublets a possible readout of motoneuron excitability. (10/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
Neuromodulation gates whether doublets occur, by facilitating NaP and reducing outward drive. This complements, rather than replaces, the classical role of neuromodulation in amplifying gain via somatodendritic PICs. A second axis, acting on spike timing. (9/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
It means an intrinsic motoneuron property that normally needs an electrode may be estimated from the firing pattern alone, a candidate non-invasive readout of single-cell biophysics in behaving humans. (8/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
Repetitive doublets adapt: the intra-doublet interval lengthens over the course of a contraction. In the model, this doublet-frequency adaptation is set by the inactivation time of the somatic NaP. The firing pattern carries a signature of an intrinsic channel property. (7/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
Initial and repetitive doublets emerge from the same mechanism. They differ only in how the second spike reaches threshold: a strong, fast input (initial) vs firing near recruitment on successive cycles (repetitive). (6/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
It is a race inside the ADP window: Ca ADP, somatic and axonal NaP, and passive current push toward threshold while the AHP pulls away. A second spike fires only if depolarization wins first. Blocking any depolarizing contributor abolishes the doublet. (5/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
Both spikes of a doublet are initiated at the axon initial segment (AIS). The second is reached when a slowly inactivating persistent Na (NaP) current at the first node of Ranvier returns toward the AIS and sums with the somatic NaP and the Ca-mediated afterdepolarization (ADP). (4/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
We combined intracellular recordings (ex vivo mouse), a three-compartment conductance-based model, and human motor unit and force data. Recordings and model converge on the same sequence. (3/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
Doublets were first observed nearly a century ago, and a doublet makes the muscle produce far more force than two separate spikes would (the catch-like property). But the underlying mechanism, including where the second spike is generated, has remained unresolved. (2/12)
100
Robin Rohlén @robinrohlen.bsky.social · 05/08/2026
New preprint! We identify the mechanism behind motoneuron doublets, closely spaced spike pairs that amplify muscle force, and show that initial and repetitive doublets share one axonal mechanism, gated by neuromodulation. www.biorxiv.org/content/10.6... (1/12)
biorxiv.org
An axonal sodium current gates motoneuron doublets and force amplification
Brief high-frequency bursts of action potentials shape neural coding. In spinal motoneurons, they appear as doublets, closely spaced spike pairs observed for a century that amplify muscle force nonlin...
100
Reposted by Robin Rohlén
bioRxiv Neuroscience @biorxiv-neursci.bsky.social · 04/05/2026
Rapid experience-dependent tuning of spinal and transcortical stretch reflexes supports goal-directed movement www.biorxiv.org/content/10.64898/20…
021
Robin Rohlén @robinrohlen.bsky.social · 08/02/2025
Curious to understand the identifiability of motor neuron spike trains from muscle activity using multichannel surface EMG or ultrasound? Here, we revisited the convolutive BSS model providing new theoretical insights verified with in silico experiments. doi.org/10.48550/arX...
doi.org
Revisiting convolutive blind source separation for identifying spiking motor neuron activity: From theory to practice
Objective: Identifying the activity of motor neurons (MNs) non-invasively is possible by decomposing signals from muscles, e.g., surface electromyography (EMG) or ultrasound. The theoretical backgroun...
021
Reposted by Robin Rohlén
Greg Pearcey @gregorypearcey.bsky.social · 02/02/2025
Abstract submission is live for the 2025 Motoneuron meeting in St. John’s, Newfoundland. Deadline for submissions is 0830 NST on March 11, 2025. If you’re interested in Motoneurons - please join us! Visit Motoneuron.org to submit!
063