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Colin Bredenberg

@colin-bredenberg.bsky.social
994 followers 648 following 17 posts

Postdoctoral researcher at the University of Montreal and Mila - Quebec AI Institute. Amateur writer.

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Colin Bredenberg @colin-bredenberg.bsky.social · 09/10/2026
Hi all, I'm happy to announce that I have started at the University of Oregon as an assistant professor! My group will use computational methods to study learning and synaptic plasticity. I will be hiring grad students this year--please reach out if you're interested! colinbre@uoregon.edu
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Charlotte Volk @charlottevolk.bsky.social · 04/08/2026
Excited to share that our paper has now been published in PLOS Computational Biology! journals.plos.org/ploscompbiol...
journals.plos.org
The curriculum effect in visual learning: The role of readout dimensionality
Author summary Learning new skills is fundamental to humans and animals. However, a key challenge in learning is generalization: applying learned skills to new situations not encountered during traini...
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Ezekiel Williams @ezekielwilliams.bsky.social · 17/06/2026
1/7 Proud to share our paper, accepted as an oral at ICML '26! We highlight how Big Tech’s influence on AI R&D drives damaging outcomes, and what we as researchers can do about it. We also discuss underlying economic causes. See link for paper, and below for a brief summary arxiv.org/abs/2512.03077
Irresponsible AI: big tech's influence on AI research and associated impacts
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Ezekiel Williams @ezekielwilliams.bsky.social · 10/06/2026
1/7 Excited to share my last PhD article, just accepted to ICML 2026! In it, we (me, Alexandre Payeur, Guillaume Lajoie) used dynamical systems theory to study "local" learning in linear recurrent neural networks. See link for the paper, and thread for a brief summary. arxiv.org/abs/2606.00243
arxiv.org
Dynamics and Representation Structure of Local Approximations to Gradient-Based Learning in Linear Recurrent Neural Networks
Biological and neuromorphic recurrent neural networks (RNNs) are subject to spatial and temporal locality constraints on the information that can plausibly be used during learning. A common strategy t...
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Pierre-Etienne Fiquet @pfiquet.bsky.social · 26/03/2026
Applications are now open for our Junior Theoretical Neuroscientists Workshop which will take place July 21 - 24, 2026 at the Center for Computational Neuroscience @flatironinstitute.org Learn more and apply by April 15 at www.simonsfoundation.org/event/jrwork...
simonsfoundation.org
Junior Theoretical Neuroscientists Workshop
Junior Theoretical Neuroscientists Workshop on Simons Foundation
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Blake Richards @tyrellturing.bsky.social · 19/03/2026
Here's a lovely #blueprint on a new study from our lab led by @royeyono.bsky.social. tl;dr: it implies that there may be interneurons whose role is to normalize credit assignment signals during learning. #neuroscience 🧪
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Colin Bredenberg @colin-bredenberg.bsky.social · 23/01/2026
We do address this in the discussion! In short, replay occurs in both REM and SW sleep, and is important for consolidation--REM replay just isn't as well-studied afaik. We think the evidence is a little stronger for this mechanism acting during REM sleep, but we cite papers supporting both phases.
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Colin Bredenberg @colin-bredenberg.bsky.social · 23/01/2026
There are closely related models that include interneuron subtypes--I'll email you some papers that discuss the role different interneuron subtypes might play in these kinds of learning algorithms. We'd have to adapt the model to include them, but it shouldn't be difficult.
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Colin Bredenberg @colin-bredenberg.bsky.social · 23/01/2026
You're right about top-down vs. bottom-up being poorly defined, esp. in association cortex. It is probably better to view this in terms of apical/basal inputs instead, and to choose a cortical area where apical inputs (e.g. higher-order thalamic inputs) have distinct (multimodal) response properties
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Colin Bredenberg @colin-bredenberg.bsky.social · 23/01/2026
Would love to chat more! Personally, I don't think that the plasticity gating mechanism in our model is very important (which is why we tested both with and without the gating). Related models (predictive coding and Boltzmann machines) don't have this gate, so it may not be necessary for learning.
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Nature @nature.com · 15/01/2026
Nature research paper: Predictive coding of reward in the hippocampus go.nature.com/49mB13V
go.nature.com
Predictive coding of reward in the hippocampus - Nature
Calcium imaging of mouse hippocampal neurons while mice learn a reward-based task over several weeks provides insight into the evolution of the hippocampal reward representation during extended periods of experience.
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Blake Richards @tyrellturing.bsky.social · 14/01/2026
Our paper on the "Oneirogen hypothesis" is now up in its revised form on eLife! This is the hypothesis that psychedelics induce a dream-like state, which we show via modelling could explain a variety of perceptual and learning effects from such drugs. elifesciences.org/reviewed-pre... 🧠📈 🧪
elifesciences.org
The oneirogen hypothesis: modeling the hallucinatory effects of classical psychedelics in terms of replay-dependent plasticity mechanisms
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A Erdem Sagtekin @aesagtekin.bsky.social · 08/01/2026
1/7 How should feedback signals influence a network during learning? Should they first adjust synaptic weights, which then indirectly change neural activity (as in backprop.)? Or should they first adjust neural activity to guide synaptic updates (e.g., target prop.)? openreview.net/forum?id=xVI...
Diagram of a recurrent neural network: input goes into the network, output is compared to a target to produce an error, and dotted feedback arrows show updates to neural activity and to synaptic weights.
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Owen Marschall @omarschall.bsky.social · 15/12/2025
1/X Excited to present this preprint on multi-tasking, with @david-g-clark.bsky.social and Ashok Litwin-Kumar! Timely too, as “low-D manifold” has been trending again. (If you read thru the end, we escape Flatland and return to the glorious high-D world we deserve.) www.biorxiv.org/content/10.6...
biorxiv.org
A theory of multi-task computation and task selection
Neural activity during the performance of a stereotyped behavioral task is often described as low-dimensional, occupying only a limited region in the space of all firing-rate patterns. This region has...
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Chen Jiang @chenjiang01.bsky.social · 04/11/2025
Excited to share that our work ‘Simultaneous detection and estimation in olfactory sensing’ with @mattyizhenghe.bsky.social, @neurovenki.bsky.social , @cpehlevan.bsky.social, @jzv.bsky.social and @paulmasset.bsky.social has been launched! 1/7
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Shahab Bakhtiari @shahabbakht.bsky.social · 15/10/2025
I have open positions for graduate students in my lab. If you’re interested in joining, please apply through the Mila form. I’m particularly interested in (thread below): 1/3 🧠🤖 #MLSky
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carolinehaimerl.bsky.social @carolinehaimerl.bsky.social · 29/07/2025
When neurons change, but behavior doesn’t: Excitability changes driving representational drift New preprint of work with Christian Machens: www.biorxiv.org/content/10.1...
biorxiv.org
Representational drift without synaptic plasticity
Neural computations support stable behavior despite relying on many dynamically changing biological processes. One such process is representational drift (RD), in which neurons' responses change over ...
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Colin Bredenberg @colin-bredenberg.bsky.social · 11/07/2025
Great review! Section 4.2 in particular looks very consistent with our 'oneirogen hypothesis' model (elifesciences.org/reviewed-pre...). You've pointed us to lots of great references for our revisions :)
elifesciences.org
The oneirogen hypothesis: modeling the hallucinatory effects of classical psychedelics in terms of replay-dependent plasticity mechanisms
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Mashbayar Tugsbayar @tmshbr.bsky.social · 15/04/2025
Top-down feedback is ubiquitous in the brain and computationally distinct, but rarely modeled in deep neural networks. What happens when a DNN has biologically-inspired top-down feedback? 🧠📈 Our new paper explores this: elifesciences.org/reviewed-pre...
elifesciences.org
Top-down feedback matters: Functional impact of brainlike connectivity motifs on audiovisual integration
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Avery HW Ryoo @averyryoo.bsky.social · 24/03/2025
Just a couple days until Cosyne - stop by [3-083] this Saturday and say hi! @nandahkrishna.bsky.social
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Brandon Munn @bmunn.bsky.social · 18/12/2024
Hi BlueSky fam, for my first post and to celebrate our recent paper being physically published I thought I’d do a summary thread! This has been my most favourite (and toughest) work to date. Please help share around!! www.cell.com/cell/abstrac... (Reach out if you can’t access)
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David Lipshutz @lipshutz.bsky.social · 09/12/2024
How do interneurons reshape neural responses? I'm excited to present work with @eerosim.bsky.social at #NeurIPS2024 that proposes a nonlinear recurrent circuit model motivated by efficient coding theory. Poster: 4:30p on Fri, Dec 13 Paper: openreview.net/forum?id=ojL...
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Jonathan Cornford @repromancer.bsky.social · 28/10/2024
Why does #compneuro need new learning methods? ANN models are usually trained with Gradient Descent (GD), which violates biological realities like Dale’s law and log-normal weights. Here we describe a superior learning algorithm for comp neuro: Exponentiated Gradients (EG)! 1/12 #neuroscience 🧪
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
11. We’re looking forward to your feedback, and we hope that some of you will be interested in testing aspects of our model!
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
10. To summarize: we’ve proposed a model of the hallucinatory effects of classical psychedelics, wherein hallucinations are caused by an increase in top-down inputs ordinarily reserved for offline generative replay underlying a form of representation learning in the brain.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
9. We conclude our study by providing a variety of testable predictions that experimental neuroscientists could use to validate or invalidate our model.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
8. Furthermore, consistent with the Entropic Brain Theory (Carhart-Harris et al. 2014), we show that simulated psychedelic administration in our model produces increases in stimulus-conditioned neural variability.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
7. Next, we show that intermediate simulated psychedelic doses in our model cause large increases in synaptic plasticity at both apical and basal synapses, as seen in (Shao et al. 2021).
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
6. We next explored how our model could explain existing neural data. First, we show that Wake-Sleep learning induces strongly correlated tuning between apical and basal dendritic compartments, as has been observed experimentally (Beaulieu-Laroche et al. 2019; O’Hare et al. 2024).
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
5. Next, we point to experimental evidence that classical psychedelics may increase the influence of apical synapses on neural activity, while decreasing the influence of basal synapses. Simulating psychedelic doses this way in our models produces highly structured hallucinations.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
We map the Wake-Sleep algorithm onto cortical architecture by proposing top-down, predictive synapses onto apical dendrites of pyramidal neurons dominate activity during the generative Sleep phase, while bottom-up synapses onto basal dendrites dominate during waking activity.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
3. An ‘oneirogen’ is a compound that makes neural activity more dream-like. We propose that psychedelics shift neural activity towards a regime normally reserved for replay during sleep, used for learning. To model this form of learning, we use the classic Wake-Sleep algorithm (Hinton et al. 1995).
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
2. We put forward the ‘Oneirogen Hypothesis,’ arguing that psychedelics cause hallucinations because they hijack a system ordinarily used for learning in the brain.
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Colin Bredenberg @colin-bredenberg.bsky.social · 08/10/2024
1. Hi all: I’m here to advertise our new preprint: www.biorxiv.org/content/10.1..., with Fabrice Normandin, @tyrellturing.bsky.social, and @glajoie.bsky.social!
biorxiv.org
The oneirogen hypothesis: modeling the hallucinatory effects of classical psychedelics in terms of replay-dependent plasticity mechanisms
Classical psychedelics induce complex visual hallucinations in humans, generating percepts that are coherent at a low level, but which have surreal, dream-like qualities at a high level. While there a...
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