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Is Learning in Biological Neural Networks Based on Stochastic Gradient Descent? An Analysis Using Stochastic
Sören Christensen1, Jan Kallsen2
1Department of Mathematics, Kiel Universiy, 24118 Kiel, Germany christensen@math.uni-kiel.de.
Neural Computation
|April 26, 2024
Summary
Learning in biological neural networks (BNNs) may use stochastic gradient descent. Our study shows that many local updates during learning opportunities approximate a gradient step, suggesting BNNs might optimize like artificial neural networks.
Area of Science:
- Computational Neuroscience
- Machine Learning Theory
Background:
- A key debate in neuroscience and AI concerns whether biological neural networks (BNNs) learn using local information only, precluding gradient-based optimization.
- Artificial neural networks (ANNs) commonly employ stochastic gradient descent (SGD) for efficient learning.
Purpose of the Study:
- To investigate the theoretical possibility of gradient-based learning in BNNs.
- To analyze a stochastic model of supervised learning in BNNs.
Main Methods:
- Development of a stochastic model for supervised learning in BNNs.
- Mathematical analysis of the conditions under which local updates approximate a continuous gradient step.
Main Results:
- Demonstration that a continuous gradient step is approximated when numerous local updates process each learning opportunity.
- Identification of a potential mechanism for gradient-based optimization within BNNs.
Conclusions:
- The findings suggest that stochastic gradient descent may indeed play a role in the optimization of biological neural networks.
- This bridges the gap between theoretical arguments against and potential biological plausibility of gradient-based learning in the brain.

