# Neural Networks - Do all neurons in hidden layer activate?

Noob question.

Okay I am beginning with MLPs and machine learning.

Suppose that I have 2 hidden layers in an ANN that uses the sigmoid function.

So does that mean that after calculating the weighted sum of inputs from the input layer all neurons in the hidden layer will only output a value between 0 and 1 in each of the neurons ?

Or will they output a weighted sum in the hidden layers and ONLY when it goes to the output neurons will the activation function be used.

• You can use the linear function, i.e. $f(x) = x$, it is even continuous, but what's the point? – Alex Jan 22 '16 at 13:05