  Strong interaction with other particles or feedback from the medium on a
Brownian particle entail memory effects in the effective dynamics. We discuss
the extension of the fluctuation-dissipation theorem to nonequilibrium Langevin
systems with memory. An important application is to the extension of the
Sutherland-Einstein relation between diffusion and mobility. Nonequilibrium
corrections include the time-correlation between the dynamical activity and the
velocity of the particle, which in turn leads to information about the
correlations between the driving force and the particle's displacement.
