McCulloch-Pitts (1943) Neuron

3. The only significant delay within the nervous system is synaptic delay

4. The activity of any inhibitory sysapse absolutely prevents excitation of the neuron at that time

5. The structure of the net does not change with time

From: A logical calculus of the ideas immanent in nervous activity. Bulletin of Mathematical Biophysics, 5, 115-133.