PNAS paper shows biological synapses can self-assemble learning rules akin to gradient descent

xuanalogue · x · 2026-10-18

In PNAS, Liu Ziyin, Tomaso Poggio and colleagues introduce Self-Assembling Learning (SAL) and the Self-Assembling Motif (SAM). Under heterosynaptic plasticity rules, SAMs emerge from initially random connectivity, and hierarchically composed SAM networks self-organize into dynamics that provably approximate generalized stochastic gradient descent, matching backpropagation-level performance. The upshot: biological learning need not be prescribed but can emerge from local rules to a far greater extent than previously thought — both the network and the learning rule itself can be learned.

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