A Logical Calculus of the Ideas Immanent in Nervous Activity
Warren McCulloch & Walter Pitts · University of Chicago
The first mathematical model of a neuron: weighted inputs summed against a threshold. Every artificial neuron since is a descendant of this one line of algebra.
y = 1 if Σ wᵢxᵢ ≥ θ, else 0
Threshold logic unit




