Chris Chatham

One of the main things neuroscientists do not like to deal with is degeneracy and the irreversibility of the activity -> function relationship, because that would force them to acknowledge that most analysis methods like decoding and functional connectivity are meaningless.

Universal scale-free representations in human visual cortex Author summary The human cerebral cortex is thought to encode sensory information in population activity patterns, but the statistical structure of these population codes has yet to be characterized. ...

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'These findings reveal high-dimensional aspects of cortical representation undetectable with conventional methods, such as RSA, & contradict previous theories suggesting that high-level visual cortex representations are low-dimensional.' #neuroskyence

journals.plos.org/ploscompbiol...

Please check out and RT this new position for an exciting collaborative project with @boninlab.bsky.social and @franckp.bsky.social on the links between human-specific mechanisms and neurodevelopmental disorders in cortical circuits.

Do you have a sense about how far this update might eventually go? I guess your conclusion may apply quite broadly... but are there particular tasks, boundary conditions, or experimental manipulations which you think are still better explained by more classical RL-like striatal processes than habit?

Very curious if this changes the conclusion from any investigational drugs tested with these tasks. I know you may not be able to say, and/or may no longer have access to those, but i assume this change is expected to alter how drug effects may translate into parameter estimates… 😎 great stuff Anne!

A structurally profound update to the most comprehensive closed-form model of working memory & RL-like interactions. Really excited to see this evolution - and to learn if this new model might tell us something different about experimental drugs tested with the older task+model. Congrats Anne

Very proud to have played a part in this work. I am confident that measurements of speech contain signal of use for developing new therapeutics, transdiagnostically...

Results so stunningly clear they inspired this classic xkcd (xkcd.com/2400/):

I remain somewhat surprised reproducing MA isn't a solved problem by all the folks scrounging around for LLM use cases. One would think that LLMs+tools would have a ready-made training set for learning RL policies on tool calls / finetuning models in the history of meta-analyses published so far.

New paper using M/EEG to look at attractive and repulsive serial dependence in working memory, led by the excellent Jiangang Shan, with Jasper Hajonides.

In fairness, I doubt this aspect of my strategy is representative. I'm also engaging in the strategy you'd assumed (although not w/ any particular hope of success, and w/ a careful eye towards poisoning myself). Anyone seen a carefully reasoned piece on the options from a relevant expert/thinktank?

One sad lesson I take from Trump 2.0 is that the majority of Americans are no longer capable of reasoned debate. So I fear any liberal worldview that ties itself to that broken vehicle is doomed. A liberal dictum to entirely avoid such spaces requires very solid justification now more than ever IMO

I understand the argument, but not the basis for believing this has any demonstrable record of success. I suspect we enable the propaganda more by evacuating the space of liberal views than we would by trying to poison the well (e.g., marking “not interested” on every ad, boycotting advertisers etc)

For one thing, it could just be another propaganda platform that we otherwise willfully grant to the right, adding to the seemingly-effective echo chambers they cultivate in various corners of the popular tech/science/lifestyle podcast world, FoxNews before that, and AM radio syndicate years earlier

No… I’m saying that despite not doing so, it may yet have value. To suggest the opposite - that its value derives exclusively from enabling debate amongst reasonable people - is potential folly, maybe one of those high-minded liberal values we need to reconsider in light of liberal losses.

Timescales of dopamine release in the striatum as a window into hierarchical control The reinforcement learning community has made significant progress in understanding dopamine (DA) in reward learning, cognitive control, and motivatio…

Proud of Amy and Nick, who review technical and theoretical gaps in timescales of dopamine fluctuations.

We argue that DA fluctuations are hierarchical control signals, and “tonic” DA relays goal alignment across planning horizons and C-BG hierarchy.

www.sciencedirect.com/science/arti...

3 reasons: (1) many folks have no idea professors also do research; (2) it may be seen as gauche to ask, and risk forcing a distinction between research faculty and teaching faculty; (3) you can still respond with how you teach (publish) about what your research has found.

I'm open to this but I question which high-minded liberal ideas need rethinking given our dismal performance among the evidently-unreasonable majority of American voters; I suspect that 'the value of a communication platform arises from its ability to engage reasonable parties in debate' may be one.

I confess I haven;t; it's a war of attrition IMO. I also don't think my contributions do much to legitimize the platform so, in the worst case, I see it mostly as a potential waste of time. I'm quote open to being persuaded, just haven't seen a comprehensive/balanced logical argument for vs against.

I also find the math unclear, and hence continue to engage there so as not to prematurely cede the ground. I concede this may not be terribly effective. But, it seems like the math must surely be clearer to you than you suggest, given the (rather ironically) extreme assertion in the OP!

This is an encouraging result for the use of EEG in a variety of applications going well beyond RSA.

Thanks for this great work! Can you explain a bit more about why you selected the similarity metrics you did? I was not sure whether there was a principled reason to use Spearman for dimensions, cosine for content and Pearson for brain or if this mixed bag of metrics simply worked best.

How Robust Are fMRI- and EEG-Based Representational Similarity Analysis? - Computational Brain & Behavior In EEG and fMRI analysis, researchers choose from a combinatorially large set of theoretically indistinguishable options while building a data processing pipeline based on individual beliefs and other...

EEG representational analyses are more robust than fMRI. Huh.

link.springer.com/article/10.1...

A systematic review of aperiodic neural activity in clinical investigations Aperiodic neural activity - activity with no characteristic frequency - has increasingly become a common feature of study, including in clinical work. Reports investigating aperiodic activity from pat...

I've updated my literature review of studies of aperiodic neural activity in clinical disorders, adding ~30 papers, taking it to 177 reports across 38 disorders!

It's got a review of results so far, discussion of themes & issues, & recommendations for future work!

www.medrxiv.org/content/10.1...

Very encouraging work; I'm inspired. What happened with the primary outcome (the LPP)? Regardless of whether the study was positive on its primary outcome, it's obvious there's something here worth exploring further. Congrats!

Confirmation bias through selective readout of information encoded in human parietal cortex Nature Communications - People often discard incoming information when it contradicts their pre-existing beliefs about the world. Here, the authors show that this discarded information is precisely...

1/ New paper by Hame Park, (@AraziAyelet), Bharath Talluri, Marco Celotto, Stefano Panzeri, Alan Stocker & Tobias Donner published in Nature Communications – “Confirmation Bias through Selective Readout of Information Encoded in Human Parietal Cortex”: rdcu.be/etlR7. Here is a summary:

Super talented team working on an incredibly important problem. Congrats!

Denali describing their approach to shuttle large molecules as cargo across the blood brain barrier. We should see new clinical data from approaches like this already in 2025. Exciting time for neurotherapeutics for this and so many other reasons...

Dual targeting of transferrin receptor and CD98hc enhances brain exposure of large molecules https://www.biorxiv.org/content/10.1101/2025.03.24.645085v1

Intellectual ability and cortical homotopy development in children and adolescents https://www.biorxiv.org/content/10.1101/2025.03.24.645014v1