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Kris Jensen @kristorpjensen.bsky.social · 13d

PFCinema strongly divided opinions among coauthors, but glad you appreciate it! 👌

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Kris Jensen @kristorpjensen.bsky.social · 13d

Thanks Hannah! Look forward to hearing what you think, and I hope everything is going well in Germany!

Kris Jensen @kristorpjensen.bsky.social · 13d

Thanks!! The whole problem of learning is something we haven't tackled yet but are very interested in! We also think that animals probably learn abstractions even in physical space, because it simplifies the planning problem by reducing the effective search space!

Kris Jensen @kristorpjensen.bsky.social · 14d

Finally a big thanks to all of our co-authors Peter Doohan, @mathiassablemeyer.bsky.social, @sandra-neuro.bsky.social, @alonbaram.bsky.social, and Thomas Akam + everyone else who contributed through discussions, ideas, and feedback!

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Kris Jensen @kristorpjensen.bsky.social · 14d

This has been a super fun project, and I’m very excited for the coming years where we will test some of the ideas experimentally together with our many excellent colleagues at the @sainsburywellcome.bsky.social and Oxford!

8/8

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Kris Jensen @kristorpjensen.bsky.social · 14d

We think PFC structures adaptive behaviour using these same principles. If true, it could provide a path towards a unified mechanistic understanding of cortical computations from the sensory periphery to high-level cognition!

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Kris Jensen @kristorpjensen.bsky.social · 14d

What is most exciting to us is that the STA solves these tasks using attractor dynamics that resemble how visual cortex infers 'missing edges' from partial inputs, how language cortex infers meaning even if we miss a word or two, and how navigation circuits infer orientation and location.

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Kris Jensen @kristorpjensen.bsky.social · 14d

RNNs trained to solve such 'PFC-like' tasks learn a solution that exactly mirrors the spacetime attractor in both representation, connectivity, and dynamics. They also reveal an elegant mechanism for rapid adaptation of a 'world model' to changing environments, without the need for plasticity!

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Kris Jensen @kristorpjensen.bsky.social · 14d

It turns out the resulting 'spacetime attractor' (STA) network is particularly good at tasks where the environment changes on a fast timescale – and these are exactly the types of behaviour that we need PFC for!

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Kris Jensen @kristorpjensen.bsky.social · 14d

We show that these representations can do much more than that. If you connect the different neural populations the right way, the resulting attractor network can infer the future! This allows the network to solve complex problems like planning using representations that we know exist in PFC.

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Kris Jensen @kristorpjensen.bsky.social · 14d

It is increasingly clear from recent work in mice and monkeys that prefrontal cortex solves sequence memory tasks by using different populations of neurons to represent different elements of the sequence.

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Kris Jensen @kristorpjensen.bsky.social · 14d

I’m super excited to finally put my recent work with @behrenstimb.bsky.social on bioRxiv, where we develop a new mechanistic theory of how PFC structures adaptive behaviour using attractor dynamics in space and time!

www.biorxiv.org/content/10.1...

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Kris Jensen @kristorpjensen.bsky.social · Mar 14

Great paper by @jonathannicholas.bsky.social and @marcelomattar.bsky.social !

A related discussion we had in our lab recently is whether there exists convincing evidence that mice use episodic memory - refs are welcome if anyone knows relevant work!

Jonathan Nicholas @jonathannicholas.bsky.social · Mar 14

Why do we remember so many details of our experiences even when it is unclear if we will actually ever need them?

In a new preprint, @marcelomattar.bsky.social and I asked whether this property is adaptive, because what will be relevant in the future often (usually?!) isn’t apparent.

Episodic memory facilitates flexible decision making via access to detailed events

Our experiences contain countless details that may be important in the future, yet we rarely know which will matter and which won't. This uncertainty poses a difficult challenge for adaptive decision ...

www.biorxiv.org

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Kris Jensen @kristorpjensen.bsky.social · Mar 6

Amazing work by Mehran, @sonjahofer.bsky.social, and colleagues, characterizing neural mechanisms underlying explore/exploit behaviours!

Sonja Hofer @sonjahofer.bsky.social · Mar 5

Should you stick to your goal, try something else, or give up? Your median raphe nucleus in the brainstem knows and will decide for you 😉. First foray of my lab into foraging, behavioural strategies and exploration. Amazing work from the one and only Mehran Ahmadlou: www.nature.com/articles/s41...

A subcortical switchboard for perseverative, exploratory and disengaged states - Nature

Behavioural experiments in mice demonstrate that GABAergic (γ-aminobutyric acid-expressing), glutamatergic and serotonergic neurons in the median raphe nucleus have distinct and complementary function...

www.nature.com

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Reposted by Kris Jensen

Stanislas Dehaene @standehaene.bsky.social · Feb 7

New paper from the lab!
Mathias Sablé-Meyer used behavior, fMRI and MEG to study the mental representation of geometric shapes (quadrilaterals ranging in regularity from squares and rectangles to random figures).
www.biorxiv.org/content/10.1...

www.biorxiv.org

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Reposted by Kris Jensen

Marine Schimel @marineschimel.bsky.social · Jan 31

For my first Bluesky post, I'm very excited to share a thread on our recent work with Mitra Javadzadeh, investigating how connections between cortical areas shape computations in the neocortex! [1/7] www.biorxiv.org/content/10.1...

Dynamic consensus-building between neocortical areas via long-range connections

The neocortex is organized into functionally specialized areas. While the functions and underlying neural circuitry of individual neocortical areas are well studied, it is unclear how these regions op...

www.biorxiv.org

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Reposted by Kris Jensen

Takaki Komiyama @takakikomiyama.bsky.social · Jan 7

663 days since the senseless tragedy that took An, we present a manuscript that reports some of the discoveries that she left us.

www.biorxiv.org/content/10.1...

Targeted stimulation of motor cortex neural ensembles drives learned movements

During the execution of learned motor skills, the neural population in the layer 2/3 (L2/3) of the primary motor cortex (M1) expresses a reproducible spatiotemporal activity pattern. It is debated whe...

www.biorxiv.org

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Kris Jensen @kristorpjensen.bsky.social · Dec 28

Glad to hear it was useful!

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Kris Jensen @kristorpjensen.bsky.social · Dec 24

(also just for those who see this post but don't find the correct other thread that resolves the original question: Xie et al. do use the smallest angle between subspaces, and the confusion arises from different definitions of 'first' principal angle)

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Kris Jensen @kristorpjensen.bsky.social · Dec 24

If you're getting into the weeds anyways, it's worth noting that (i) just doing svds on noisy data actually yields biased estimates, and (ii) it turns out the subspaces are slightly correlated and this is expected from theory.

Ref: excellent work by Will Dorrell & co. (arxiv.org/abs/2410.06232)

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Kris Jensen @kristorpjensen.bsky.social · Dec 24

From a brief look at their code, they call base matlab svd, which returns the singular values in descending order, corresponding to the angles in ascending order - so I think everything is correct!

Kris Jensen @kristorpjensen.bsky.social · Dec 23

www.science.org/doi/10.1126/...

This work on sequence working memory from Liping Wang's lab is super cool!

TLDR: when macaques remember a sequence, ~orthogonal neural subspaces in DLPFC store the identity of the item at each index of the sequence

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Kris Jensen @kristorpjensen.bsky.social · Dec 23

I agree that the focus on these results has diminished in recent years. Possibly a result of the rise of ML, where the focus is more on algorithms and performance over qualitative behaviours? A more positive take is that we do incorporate this understanding by building on prior modelling work.

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Kris Jensen @kristorpjensen.bsky.social · Dec 23

Thanks!!

I do think quite a lot of the work from behavioural psychology has carried over to cognitive/neuroscience - people still talk about Pavlovian & instrumental conditioning, effects like blocking, etc. These effects also heavily inspired early computational modelling (e.g. Rescola-Wagner).

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Kris Jensen @kristorpjensen.bsky.social · Dec 21

For those who are interested, I also wrote a Colab notebook that implements some of these RL algorithms and reproduces all the figures from the review: colab.research.google.com/drive/1ZC4lR...

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