iiinova — where your digital self keeps evolving

Fin/ check out the paper at www.nature.com/articles/s41...! Huge thanks to Pia O'Neill (new assistant prof at Dartmouth sites.dartmouth.edu/oneill-lab/) for leading this project, and to @stefanofusi.bsky.social & Daniel Salzman for the fantastic collaboration! Cover artwork matteofarinella.com/

The representational geometry of emotional states in basolateral amygdala - Nature Neuroscience

O’Neill, Posani and colleagues show that while single amygdala neurons encode multiple emotional state-related variables (for example, valence, fear and safety), population-level geometry can enable o...

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The representational geometry of emotional states in basolateral amygdala - Nature Neuroscience

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12/ In short, specialized readouts can be supported by a neural population even with mixed selectivity, as long as the geometry is right. We find that BLA simultaneously encodes multiple variables within an emotional experience, with the right geometry for specialized readouts.

11/ The geometry then changes after ingressing, and the mouse no longer represents valence. Instead, only the exposed, aversive condition stands out from the bulk. This is compatible with the coding of a new variable, "safety", which has the highest decoding and CCGP.

10/ Crucially, it does so without specialized populations! Selectivity is largely mixed across all variables:

9/ This is indeed what we observe in the BLA: it represents behavioral and valence variables as "abstract", with a disentangled compositional geometry, characterized by a high CCGP (generalization) and low CVI (interference):

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8/ The key is that specialized neurons are not necessary to satisfy these requirements! We can have the same properties (high CCGP, low CVI) as long as the representational geometry of the encoded variables is disentangled / compositional (left panel):

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7/ But we can also characterize these properties (high generalization, low interference) on a population level. For generalization, we can use cross-condition generalization performance (CCGP). For interference, we developed a new measure: cross-variable interference (CVI):

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6/ A circuit made of specialized sub-populations, such as "valence neurons" and "tremble neurons", clearly satisfies these requirements: sub-populations encode variables independently, and each trivially generalizes across contexts because it cares about only one thing.

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5/ For example, to make quick, precise decisions when faced with threats, the brain needs to read out information precisely (low interference) and flexibly (high generalization) - this is a "specialized" circuit. How can we design one?

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4/ What about the neural code? All variables were highly decodable, but representing the world is not enough to act on it. What matters is "how" this information is organized!

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3/ Both trembling and freezing are more frequent in response to aversive odors (CS+), but far from exclusive. Mice typically tremble and then ingress when CS+ is presented, in accordance with the predator-imminence theory (freeze -> flee).

2/ The BLA is known to have specialized circuits for valence (+/-), but what about other features of emotional experiences, such as behavior? In a virtual burrow assay, we observed that mice both tremble (~freeze) and ingress (~flee) in response to aversive (shock-paired) odors.

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Abid Hussaini @hussainilab.bsky.social · 31/07/2026

For a neural circuit to be "specialized", does it need specialized neurons? In our new work - now out in @NatureNeuro - we address this question in the BLA, using representational geometry to propose a new population-centric way of defining circuit specialization. 🧵👇 1/

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Reposted by Lorenzo Posani

Very proud to announce our recently published paper led by Gustavo Rodriguez et al. Impaired spatial coding and neuronal hyperactivity in the medial entorhinal cortex of aged APP knock-in mice: www.cell.com/cell-reports...

cell.com

Impaired spatial coding and neuronal hyperactivity in the medial entorhinal cortex of aged APP knock-in mice

Using the Earth Mover’s Distance and machine learning techniques, Rodriguez et al. show increased instability in spatial representations and impaired spatial information coding in the medial entorhina...

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Lorenzo Posani @lorenzoposani.com · 30/07/2026

Great to see this out! Big congrats Jen!!

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Reposted by Lorenzo Posani

Earl K. Miller @earlkmiller.bsky.social · 28/07/2026

Most neurons seem to be generalists, not specialists. Cortical circuits prioritize diversity over categorical structure. Rarely categorical, highly separable representations along the cortical hierarchy www.nature.com/articles/s41... #neuroscience www.newscientist.com/article/2581...

Rarely categorical, highly separable representations along the cortical hierarchy - Nature

Cortical circuits prioritize diversity over categorical structure, supporting a computational regime geared towards high-dimensional, highly separable neural representations.

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Reposted by Lorenzo Posani

neurosock @neurosock.bsky.social · 16/07/2026

This recent post by @earlkmiller.bsky.social got my attention. It shows how abstraction could emerge in the primate PFC. The paper is hard, but the main idea can be simplified to low-dims, so I made fun a little animation. A🧵with my toy model and notes: #neuroskyence #compneuro #NeuroAI

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Lorenzo Posani @lorenzoposani.com · 16/07/2026

Thank you Brian! Looking forward to working with you 😊

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Reposted by Lorenzo Posani

Columbia University's Zuckerman Institute @zuckermanbrain.bsky.social · 15/07/2026

Scientists have long debated whether neurons are jacks of all trades or tend to specialize in one thing. Now @stefanofusi.bsky.social, @lorenzoposani.com & Liam Paninski present new evidence in @nature.com shedding light on how the brain performs complex tasks. tinyurl.com/yj3ew8en

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Reposted by Lorenzo Posani

Shuqi Wang @shuqiw.bsky.social · 15/07/2026

Our paper "Rarely categorical, highly separable representations along the cortical hierarchy" is now out in Nature! www.nature.com/articles/s41... In this paper, we studied whether the brain is well-organized and interpretable, both globally and locally. (See thread below.)