Credit to Sherry An who did most of the work here, and the other co-authors, Josh Glaser (@joshuaiglaser.bsky.social), Lee Miller, and Kyle Blum. Here's the link again--hope you check it out!
doi.org/10.64898/202...
11/11
Altogether, these results suggest that the orthogonality of CD and FB signals in area 2 enable flexible integration downstream for either body state estimation or for adapting to external perturbation 10/
Bump classification performance for orthogonal, aligned, and opposite geometry of CD and FB signals
At the same time, we found that for trying to detect external perturbations, the orthogonal and opposite geometries could succeed, but the aligned geometry could not. 9/
State estimation performance in models using orthogonal, aligned, and opposite geometry of CD and FB signals
What benefit might there be to keeping these signals separate and orthogonal? We simulated various geometries to find out. We found that both orthogonal and aligned geometries could combine the two signals for better state estimation, but an opposed geometry could not. 8/
Histogram of Monte Carlo analysis on principal angles between corollary discharge and feedback signal subspaces
CD and FB signals in area 2 also seem to be orthogonal to each other in the full neural state space. This echos similar findings in other cortical areas, showing that, for example, motor preparation and execution lie in orthogonal neural subspaces. 7/
Example corollary discharge and feedback signal dimensions during passive perturbation trials
However, for passive trials (unseen by the decoding procedure), this relationship is reversed--FB dimensions come on first, and CD signals come on later, likely to coordinate the active return reach. 6/
Example corollary discharge and feedback signal dimensions during active reaching trials
Using an iterative decoding procedure in each of these active trial epochs, we isolated CD and FB signals. For active trials, as we would expect, we found that CD signals start before movement, and then reverse direction for the return reach. FB signals look similar, but delayed. 5/
Diagram showing the epochs where corollary discharge and feedback signals can be isolated during active reaching
In active reaching trials, we would expect corollary discharge (CD) signals, but not feedback (FB) signals, to be present in neural activity just before the reach. Likewise, just before the end of the reach, we would expect primarily feedback signals. 4/
Task diagram showing time course and hand trajectories of an active and passive task
To look for neural evidence of this integration, we recorded from area 2 of somatosensory cortex as monkeys actively reached to targets and were passively perturbed. 3/
Block diagram showing integration of sensory feedback and corollary discharge for motor control
Most of us interact with the world without thinking about how. A big part of this ability is sensory feedback about body movement, but because of pathway delays, we can't rely only on feedback. Instead, we integrate feedback with motor signals ("corollary discharge") into an estimated body state. 2/
Neural trajectory plot showing neural activity moving through orthogonal corollary discharge and feedback signal subspaces
New preprint! 🧵🧪🧠
doi.org/10.64898/202...
Upshot: somatosensory cortex contains both feedback *and* intended movement signals (a.k.a. corollary discharge). These two signals exist orthogonally in neural space, flexibly allowing both fast state estimation and external perturbation detection. 1/
Bump classification performance for orthogonal, aligned, and opposite geometry of CD and FB signals
At the same time, we found that for trying to detect external perturbations, the orthogonal and opposite geometries could succeed, but the aligned geometry could not. 9/
State estimation performance in models using orthogonal, aligned, and opposite geometry of CD and FB signals
What benefit might there be to keeping these signals separate and orthogonal? We simulated various geometries to find out. We found that both orthogonal and aligned geometries could combine the two signals for better state estimation, but an opposed geometry could not. 8/
Histogram of Monte Carlo analysis on principal angles between corollary discharge and feedback signal subspaces
CD and FB signals in area 2 also seem to be orthogonal to each other in the full neural state space. This echos similar findings in other cortical areas, showing that, for example, motor preparation and execution lie in orthogonal neural subspaces. 7/
Example corollary discharge and feedback signal dimensions during passive perturbation trials
However, for passive trials (unseen by the decoding procedure), this relationship is reversed--FB dimensions come on first, and CD signals come on later, likely to coordinate the active return reach. 6/
Example corollary discharge and feedback signal dimensions during active reaching trials
Using an iterative decoding procedure in each of these active trial epochs, we isolated CD and FB signals. For active trials, as we would expect, we found that CD signals start before movement, and then reverse direction for the return reach. FB signals look similar, but delayed. 5/
Diagram showing the epochs where corollary discharge and feedback signals can be isolated during active reaching
In active reaching trials, we would expect corollary discharge (CD) signals, but not feedback (FB) signals, to be present in neural activity just before the reach. Likewise, just before the end of the reach, we would expect primarily feedback signals. 4/
Task diagram showing time course and hand trajectories of an active and passive task
To look for neural evidence of this integration, we recorded from area 2 of somatosensory cortex as monkeys actively reached to targets and were passively perturbed. 3/
Block diagram showing integration of sensory feedback and corollary discharge for motor control
Most of us interact with the world without thinking about how. A big part of this ability is sensory feedback about body movement, but because of pathway delays, we can't rely only on feedback. Instead, we integrate feedback with motor signals ("corollary discharge") into an estimated body state. 2/
New paper hot off the (pre-)press! We dig into the evolutionary origins of neural computations for behavioral control across mice, monkeys, and humans: www.biorxiv.org/content/10.6....
As our lab's first foray into comparative analysis of neural dynamics, I’m super excited about this work! 1/18
🚨📜+🧵🚨 Very excited about this work showing that people with no hand function following a spinal cord injury can control the activity of motor units from those muscles to perform 1D, 2D and 3D tasks, play video games, or navigate a virtual wheelchair
By a wonderful team co-mentored w Dario Farina
When you fail to perform at your best right when it matters the most, what's going on in your brain? We can now provide an explanation: Exceptionally high stakes interfere with the neural signals of motor preparation. I'd love to hear - what do you think causes it?
sciencedirect.com/science/arti...
Just created a list with the sensorimotor people I was following/followed me (inclusion criteria slightly generous)
Let me know if you want to be added, and repost (?) to spread the word go.bsky.app/U4oyFgw