Visual motion estimation is a computationally intensive,
but important task for sighted animals. Replicating the
robustness and efficiency of biological visual motion estimation in
artificial systems would significantly enhance the capabilities of
future robotic agents. 25 years ago, in this very journal, Carver
Mead outlined his argument for replicating biological processing
in silicon circuits. His vision served as the foundation for the
field of neuromorphic engineering, which has experienced a rapid
growth in interest over recent years as the ideas and technologies
mature. Replicating biological visual sensing was one of the first
tasks attempted in the neuromorphic field. In this paper we focus
specifically on the task of visual motion estimation. We describe
the task itself, present the progression of works from the early
first attempts through to the modern day state-of-the-art, and
provide an outlook for future directions in the field.