In 1943 McCulloch & Pitts developed a Boolean circuit model of brain.
They wrote the paper “A Logical Calculus of Ideas Immanent in Nervous Activity”, which explained how it is possible for neural networks to compute.
Marvin Minsky and Dean Edmonds built the SNARC in 1951, which is the first randomly wired neural network learning machine (SNARC stands for Stochastic Neural-Analog Reinforcement Computer).
It was a neural network computer that used 3000 vacuum tubes and a network with 40 neurons.