Components of a McCullochPitts neuron
Excitatory inputs, x_{i:}
Excitatory inputs have values in {0, 1}. Each one contributes equally
to the activation of the unit.
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Inhibitory inputs, x_{n+j}:
Inhibitory inputs have values in {0, 1}.
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Threshold, u:
The threshold is an integer (it could be any real number, but there is
no point in this!).
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Neuron Output, y:
The output, whose values are in {0, 1}, is computed as follows.

If a unit has at least one inhibitory input whose value is 1, then the
unit is inhibited and its output is 0, regardless of the excitatory inputs.

Provided the unit is not inhibited, its total excitation is computed
by summing the n excitatory inputs: x = x1 + x2 + ... + xn.

The result is compared with the threshold u. If x >= u the unit output
is set to 1, and if x < u then the output is 0. (I.e., the McCullochPitts
neuron has a unit step activation function.)
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