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Hannes Mehrer @hannesmehrer.bsky.social · 9h

Thanks for the question, Konrad! Do you mean what percentage of variance of the neural effects of perturbations our topo models can explain? Would be great if we could investigate that, but we haven't recorded neural data during perturbation trials. Or what did you mean by observational data?

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

@neuroxepfl.bsky.social @icepfl.bsky.social @epfl-ai-center.bsky.social

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Special thanks go out to Paolo Papale and Anna Mitola who initiated this collaboration and performed the in-vivo experiments. And to the rest of a great team: Ben Lonnqvist @benlonnqvist.bsky.social, Abdulkadir Gokce @akgokce.bsky.social, Martin Schrimpf @mschrimpf.bsky.social

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Take-home-message

Proof-of-principle that topographic models can guide stimulation of high-level cortex to bias object-level behavioral choices. A step toward next-generation visual prosthetics allowing more complex visual experience.

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Model perceptual changes via simulated microstimulation

We visualized perceptual changes from simulated stimulations in model face-selective regions. This results in face-related changes: additional faces appear (#1), face becomes larger (#1161), or specific face-features get enhanced (#533).

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Experiment 2

With a slightly different site-selection criterion, stimulation shifted behavior above baseline in monkey 1 (Cohen’s d=0.67), though our model was not able to accurately predict monkey behavior anymore.

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Experiment 1

Model-predicted behavioral shifts correlated with stimulation-evoked behavioral shifts in both monkeys. While predicted model responses were strong, monkey behavior was not shifted above baseline.

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Visual stimuli via GANs

We generate image sequences that smoothly modulate neural activity along a stimulation site’s tuning dimension. This links visual input to the direction of activation changes resulting from microstimulation (Papale et al. 2024: www.biorxiv.org/content/10.1...)

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

How it works

1. Map the in-silico cortical sheet of a topographic model to the monkey cortex.
2. Optimize stimulation parameters by prototyping experiments in the model.
3. Only test those parameters in-vivo that are predicted to yield the largest behavioral effects.

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Stimulate high-level vs early visual cortex

Visual prosthetics in early visual areas can evoke simple percepts (letters), but they are limited by 1. electrode count and 2. low-level features. We target high-level cortex to elicit percepts of more complex objects.

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

🧠 New preprint: we show that model-guided microstimulation can steer monkey visual behavior.

Paper: arxiv.org/abs/2510.03684

🧵

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Hannes Mehrer @hannesmehrer.bsky.social · 1d

Take-home-message

Proof-of-principle that topographic models can guide stimulation of high-level cortex to bias object-level behavioral choices. A step toward next-generation visual prosthetics allowing ore complex visual experience.

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Model perceptual changes via simulated microstimulation

We visualized perceptual changes from simulated stimulations in model face-selective regions. This results in face-related changes: additional faces appear (#1), face becomes larger (#1161), or specific face-features get enhanced (#533).

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Model perceptual changes via simulated microstimulation

We visualized perceptual changes from simulated stimulations in model face-selective regions. This results in face-related changes: additional faces appear (#1), face becomes larger (#1161), or specific face-features get enhanced (#533).

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Experiment 2

With a slightly different site-selection criterion, stimulation shifted behavior above baseline in monkey 1 (Cohen’s d=0.67), though our model was not able to accurately predict monkey behavior anymore.

1

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Experiment 1

Model-predicted behavioral shifts correlated with stimulation-evoked behavioral shifts in both monkeys. While predicted model responses were strong, monkey behavior was not shifted above baseline.

1

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Visual stimuli via GANs

We generate image sequences that smoothly modulate neural activity along a stimulation site’s tuning dimension. This links visual input to the direction of activation changes resulting from microstimulation (Papale et al. 2024: www.biorxiv.org/content/10.1...)

1

Hannes Mehrer @hannesmehrer.bsky.social · 1d

How it works

1. Map the in-silico cortical sheet of a topographic model to the monkey cortex.
2. Optimize stimulation parameters by prototyping experiments in the model.
3. Only test those parameters in-vivo that are predicted to yield the largest behavioral effects.

1

Hannes Mehrer @hannesmehrer.bsky.social · 1d

Stimulate high-level vs early visual cortex

Visual prosthetics in early visual areas can evoke simple percepts (letters), but they are limited by 1. electrode count and 2. low-level features. We target high-level cortex to elicit pecepts of more complex objects.

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Hannes Mehrer @hannesmehrer.bsky.social · 6d

Very happy to be part of this project: Melika Honarmand has done a great job of using vision-language-models to predict the behavior of people with dyslexia. A first step toward modeling various disease states using artificial neural networks.

Martin Schrimpf @mschrimpf.bsky.social · 6d

I've been arguing that #NeuroAI should model the brain in health *and* in disease -- very excited to share a first step from Melika Honarmand: inducing dyslexia in vision-language-models via targeted perturbations of visual-word-form units (analogous to human VWFA) 🧠🤖🧪 arxiv.org/abs/2509.24597

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Reposted by Hannes Mehrer

Anita Devineni @anitadevineni.bsky.social · 8d

My department at Emory is a hiring a tenure-track neuroscientist!

Anyone who's talked to me in the last 4 years knows I cannot say enough good things about my dept and the neuroscience community here. My colleagues are so wonderfully supportive. Postdocs, please apply!

apply.interfolio.com/174371

Apply - Interfolio {{$ctrl.$state.data.pageTitle}} - Apply - Interfolio

apply.interfolio.com

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Reposted by Hannes Mehrer

Brokoslaw Laschowski @drlaschowski.bsky.social · Jun 26

Are you a graduate student in #Ukraine interested in machine learning and neuroscience? My research lab at #UofT is now accepting applications for remote thesis supervision.

(1/3) #neuroAI #compneuro @vectorinstitute.ai @uoft.bsky.social @uoftcompsci.bsky.social @uhn.ca

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Reposted by Hannes Mehrer

Dan Yamins @dyamins.bsky.social · 23d

Here is our best thinking about how to make world models. I would apologize for it being a massive 40-page behemoth, but it's worth reading. arxiv.org/pdf/2509.09737

arxiv.org

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Reposted by Hannes Mehrer

Brokoslaw Laschowski @drlaschowski.bsky.social · Sep 5

Come join us at University of Toronto. We're hiring a Professor of computational cognitive neuroscience.

#neuroAI #compneuro jobs.utoronto.ca/job/Toronto-...

Professor - Computational Cognitive Neuroscience

jobs.utoronto.ca

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Reposted by Hannes Mehrer

Russ Poldrack @russpoldrack.org · 26d

Great explainer on variance partitioning

Jörn Diedrichsen @diedrichsenjorn.bsky.social · 28d

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...

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Reposted by Hannes Mehrer

aaron bornstein @aaronbornstein.bsky.social · 27d

Come work with us! UC Irvine Cognitive Sciences is looking for a new Assistant Professor to join our team: recruit.ap.uci.edu/JPF09896

I'm not on the committee, but happy to talk if you're interested.

Assistant Professor - Cognitive Sciences

University of California, Irvine is hiring. Apply now!

recruit.ap.uci.edu

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