A peregrine falcon will reach speeds of 200 miles per hour as it hurtles
towards its prey – a pigeon that is itself in full flight as it
attempts to escape the looming predator. Despite the speeds involved,
the peregrine will still successfully adjust its position to elegantly
and precisely intercept its prey. Ants who have successfully navigated
the long distance between their foraging spot and their nest dozens of
times will drastically overshoot their destination if the size of their
legs are doubled by the addition of stilts. These are just two examples
of the crucial relationship between the speed of movement and successful
navigation strategies. They necessitate that animals keep track of their
movement speed and use it to precisely and instantly modify where they
think they are and where they want to go. Here we review the heavily
interconnected neural circuitry that has evolved to integrate speed and
space in the brain. We start with the rate and temporal codes for speed
in the hippocampus and work backwards towards both the motor and sensory
systems. As we trace the flow of the speed signal across these circuits,
we highlight the need to design experiments that systematically attempt
to differentiate the respective contributions of motor efference copy
and sensory inputs. In particular, we emphasize the importance of
high-resolution, precise tracking of the latency of speed-encoding
compared to the actual change in speed as a precise way to disentangle
the sensory versus motor computations that enable successful spatial
navigation at very different speeds.