Cell motility as a persistent random walk

We study the stochastic properties of trajectories of individual keratocytes that move on a solid substrate. The distribution of observed velocities exhibits a characteristic maximum at finite speed and a local minimum at zero velocity. This velocity distribution depends on the averaging time during which velocities are measured. To characterize the stochatsic properties of the system, we determine the correlations between longitudinal and transverse components of the acceleration with the instantaneous velocity. The experimental data can be captured by a simplified physical description of cell locomotion where random forces act on a system of two elastically coupled elements, one of which is driven forward by an active process, dragging the second behind.