Publications by Johanni Michael Brea

Computational models of episodic-like memory in food-caching birds

How the 'what', 'where', and 'when' of past experiences are stored in episodic memories and retrieved for suitable decisions remains unclear. In an effort to address these questions, the authors present computational models of neural networks that behave l ...

NATURE PORTFOLIO2023

Surprise and novelty in the brain

Wulfram Gerstner, Johanni Michael Brea, Alireza Modirshanechi, Sophia Becker

Notions of surprise and novelty have been used in various experimental and theoretical studies across multiple brain areas and species. However, 'surprise' and 'novelty' refer to different quantities in different studies, which raises concerns about whethe ...

CURRENT BIOLOGY LTD2023

Brain signals of a Surprise-Actor-Critic model: Evidence for multiple learning modules in human decision making

Wulfram Gerstner, Johanni Michael Brea, Alireza Modirshanechi, Kerstin Preuschoff, Marco Philipp Lehmann, Vasiliki Liakoni

Learning how to reach a reward over long series of actions is a remarkable capability of humans, and potentially guided by multiple parallel learning modules. Current brain imaging of learning modules is limited by (i) simple experimental paradigms, (ii) e ...

ACADEMIC PRESS INC ELSEVIER SCIENCE2022

A taxonomy of surprise definitions

Wulfram Gerstner, Johanni Michael Brea, Alireza Modirshanechi

Surprising events trigger measurable brain activity and influence human behavior by affecting learning, memory, and decision-making. Currently there is, however, no consensus on the definition of surprise. Here we identify 18 mathematical definitions of su ...

2022

Kernel Memory Networks: A Unifying Framework for Memory Modeling

Wulfram Gerstner, Johanni Michael Brea, Georgios Iatropoulos

We consider the problem of training a neural network to store a set of patterns with maximal noise robustness. A solution, in terms of optimal weights and state update rules, is derived by training each individual neuron to perform either kernel classifica ...

2022

Fitting summary statistics of neural data with a differentiable spiking network simulator

Wulfram Gerstner, Johanni Michael Brea, Alireza Modirshanechi, Shuqi Wang

Fitting network models to neural activity is an important tool in neuroscience. A popular approach is to model a brain area with a probabilistic recurrent spiking network whose parameters maximize the likelihood of the recorded activity. Although this is w ...

2021

Geometry of the Loss Landscape in Overparameterized Neural Networks: Symmetries and Invariances

Wulfram Gerstner, Clément Hongler, Johanni Michael Brea, Francesco Spadaro, Berfin Simsek, Arthur Jacot

We study how permutation symmetries in overparameterized multi-layer neural networks generate `symmetry-induced' critical points. Assuming a network with

L

layers of minimal widths

r_1^*, \ldots, r_{L-1}^*

reaches a zero-loss minimum at $ r_1^*! \c ...

2021

Learning in Volatile Environments With the Bayes Factor Surprise

Wulfram Gerstner, Johanni Michael Brea, Alireza Modirshanechi, Vasiliki Liakoni

Surprise-based learning allows agents to rapidly adapt to nonstationary stochastic environments characterized by sudden changes. We show that exact Bayesian inference in a hierarchical model gives rise to a surprise-modulated trade-off between forgetting o ...

MIT PRESS2021

Testing two competing hypotheses for Eurasian jays' caching for the future

Johanni Michael Brea

Previous research reported that corvids preferentially cache food in a location where no food will be available or cache more of a specific food in a location where this food will not be available. Here, we consider possible explanations for these prospect ...

NATURE RESEARCH2021

On the choice of metric in gradient-based theories of brain function

Wulfram Gerstner, Johanni Michael Brea, Jean-Pascal Théodor Pfister

The idea that the brain functions so as to minimize certain costs pervades theoretical neuroscience. Because a cost function by itself does not predict how the brain finds its minima, additional assumptions about the optimization method need to be made to ...

2020

Johanni Michael Brea

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Computational models of episodic-like memory in food-caching birds

Surprise and novelty in the brain

Brain signals of a Surprise-Actor-Critic model: Evidence for multiple learning modules in human decision making

A taxonomy of surprise definitions

Kernel Memory Networks: A Unifying Framework for Memory Modeling

Fitting summary statistics of neural data with a differentiable spiking network simulator

Geometry of the Loss Landscape in Overparameterized Neural Networks: Symmetries and Invariances

Learning in Volatile Environments With the Bayes Factor Surprise

Testing two competing hypotheses for Eurasian jays' caching for the future

On the choice of metric in gradient-based theories of brain function

Geometry of the Loss Landscape in Overparameterized Neural Networks: Symmetries and Invariances

Computational models of episodic-like memory in food-caching birds

Surprise and novelty in the brain

Brain signals of a Surprise-Actor-Critic model: Evidence for multiple learning modules in human decision making

A taxonomy of surprise definitions

Kernel Memory Networks: A Unifying Framework for Memory Modeling

Fitting summary statistics of neural data with a differentiable spiking network simulator

Learning in Volatile Environments With the Bayes Factor Surprise

Testing two competing hypotheses for Eurasian jays' caching for the future

On the choice of metric in gradient-based theories of brain function