Mehrdad Kashefi

Reward-driven emergence of auditory pattern encoding in the primate motor system The ability to anticipate rhythmic patterns is fundamental to human experience, enabling music appreciation, speech comprehension, and dancing in sync to music. How the brain learns to use acoustic information to guide motor behavior remains a key question whose neural underpinnings and evolutionary origins are debated, especially in non-human primates. To understand how brain areas involved in motor control naively respond to predictable tone patterns, we recorded large single neuron populations across primary somatosensory (S1), primary motor (M1), dorsal premotor (PMd), supplementary motor (SMA), pre-supplementary motor (preSMA) cortices, globus pallidus interna (GPi), and medial geniculate body (MGB) of a rhesus monkey. During passive listening (Experiment 1) with a reward only at the end of each trial, primarily the MGB, not motor areas, responded to the auditory tone patterns, ruling out the spontaneous entrainment of motor activity to auditory patterns. Almost all areas robustly

While humans spontaneously dance to a beat, the evolutionary origins of this ability remain debated. Behavioral work has shown that primates can move to auditory rhythms after training.

Our question was: How does this association emerge in the brain?

www.biorxiv.org/content/10....

This week's sensorimotor superlab reading list is out https://superlab.ca/posts/2025-12-19-list316.html @andpru.bsky.social @diedrichsenjorn.bsky.social @gribblelab.org #neuroskyence #psychscisky #Sensorimotor

Are you interested in a MSc/PhD in human sensorimotor neuroscience? Learn to design experiments, analyze data, read & write papers, present at conferences, & work with a vibrant group of students & faculty in a world-class research environment.
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Sequence preparation is not always associated with a reaction time cost The extent to which a sequence of movements is prepared before initiating the first movement is a longstanding question in motor neuroscience. The observation that reaction time (RT) increases for lon...

0/7 Excited to 📢 that our (@mkashefi.bsky.social @diedrichsenjorn.bsky.social @andpru.bsky.social) new preprint on sequence preparation and its effect on reaction time is now up: www.biorxiv.org/content/10.1...
Please get in touch if there is anything you'd like to discuss! Brief summary 🧵👇

Thanks Jon!

Sensory expectations shape neural population dynamics in motor circuits Nature - Experiments with human volunteers and macaques show that expectations produced by probabilistic cueing of future sensory inputs shape motor circuit dynamics in order to increase the...

Thrilled that our paper is out today in Nature!
www.nature.com/articles/s4...

The neural control & computation lab is recruiting!

If you're interested in using large-scale neural population recordings to study how the brain learns to produce complex and flexible behaviours, please get in touch.

www.ncclab.ca

This week's sensorimotor superlab reading list is out https://superlab.ca/posts/2025-09-12-list303.html @andpru.bsky.social @diedrichsenjorn.bsky.social @gribblelab.org #neuroskyence #psychscisky #Sensorimotor

Variance partitioning is used to quantify the overlap of two models. Over the years, I have found that this can be a very confusing and misleading concept. So we finally we decided to write a short blog to explain why.
@martinhebart.bsky.social @gallantlab.org
diedrichsenlab.org/BrainDataSci...

New preprint from the lab! 🧠
Led by Juliana Trach, w/ Sophia Ou

Using fMRI, we discovered evidence for time-sensitive reward prediction errors (RPEs) in the human cerebellum.

Builds on, and extends, recent work in both rodents and NHPs

Exited to share tomorrow new updates on trying to figure out how the neocortex and cerebellum talk to each other. Work by @carobellum.bsky.social, Ali Shabazi, and others in the lab!

Thanks Josh!

Thanks Mahdiyar!

Thanks Harrison!

Compositional neural dynamics during reaching The complex mechanics of the arm make the neural control of reaching inherently posture dependent. Because previous reaching studies confound reach direction with final posture, it remains unknown how...

Thanks for reading 🙏 The paper also covers recordings from SMA, pre-SMA, dlPFC & GPi.
Full details here ⬇️ www.biorxiv.org/content/10.1...
10/10

Conclusion: Motor cortex dynamics are compositional. They simultaneously:
- generate movement
- maintain an internal representation of posture
- track task progress
9/10

Modeling: Using modular RNNs, we asked what’s required for this compositional structure to emerge. It turns out this solution is common whenever the effector is complex enough to demand posture-dependent control policies. 8/10

3️⃣ A condition-independent shift dimension: a trajectory reflecting trial progression, unfolding similarly across all movements, regardless of direction or posture. 7/10

2️⃣ Rotational dynamics: transitions linking posture-specific fixed points.These rotations were systematic—similar rotations produced similar reach directions—and their projection continuously updated posture. 6/10

Key finding: High-density recordings from M1 & PMd revealed a compositional neural geometry with 3 components. 1️⃣ A posture subspace: fixed points for each target, visited whenever the arm rested at that location before or after a reach. 5/10

Our approach: We trained monkeys to reach between all pairs of 5 targets. Each target was a start point on some trials and an end point on others. This design let us dissociate posture representations from movement dynamics. 4/10

Why this problem exists: Most insights come from center-out tasks, where all movements start from one spot. Here, reach direction and final posture are always correlated—making it impossible to separate movement dynamics from posture encoding. 3/10

The problem: Moving your arm to grab coffee requires different muscle commands depending on where your arm starts. We know the brain must incorporate posture when planning movement—but how neural dynamics achieve this remains unclear. 2/10

Compositional neural dynamics during reaching The complex mechanics of the arm make the neural control of reaching inherently posture dependent. Because previous reaching studies confound reach direction with final posture, it remains unknown how...

Excited to share my latest work with @jonathanamichaels.bsky.social @diedrichsenjorn.bsky.social & @andpru.bsky.social!
We asked: How does the motor cortex account for arm posture when generating movement?
Paper 👉 www.biorxiv.org/content/10.1...
1/10

Thanks! This is highly relevant to our work.

If this doesn't solve the issue send me an email. Happy to chat more about it!

If that were the case, I would expect this representation to transfer across effectors—especially when the visual sequence remains identical. However, this isn’t what we observe in our data (see Experiment 2 in the paper).

Hi Alfred Nobel! Thanks for your interest! If I understand you correctly, you're suggesting that participants might form a purely cognitive representation of the sequence "shape."

We're excited to share our new paper: “cTBS of prefrontal cortex in the behaving macaque: no evidence for within-target inhibition or cross-hemisphere disinhibition of neural activity”
tinyurl.com/cTBSPFCNHP
w/ @brian-corneil.bsky.social

What did we find? Mostly... what we didn’t! 🧵

✋