  The present article analyses the impact on cosmology, in particular on the
evolution of cosmological perturbations, of the existence of extra-dimensions.
The model considered here is that of a five-dimensional Anti-de Sitter
spacetime where ordinary matter is confined to a brane-universe. The
homogeneous cosmology is recalled. The equations governing the evolution of
cosmological perturbations are presented in the most transparent way: they are
rewritten in a form very close to the equations of standard cosmology with two
types of corrections: a. corrections due to the unconventional evolution of the
homogeneous solution, which change the background-dependent coefficients of the
equations; b. corrections due to the curvature along the fifth dimension, which
act as source terms in the evolution equations.
