  Originally inspired by neurobiology, deep neural network models have become a
powerful tool of machine learning and artificial intelligence, where they are
used to approximate functions and dynamics by learning from examples. Here we
give a brief introduction to neural network models and deep learning for
biologists. We introduce feedforward and recurrent networks and explain the
expressive power of this modeling framework and the backpropagation algorithm
for setting the parameters. Finally, we consider how deep neural networks might
help us understand the brain's computations.
