  Bayer and Blanco-Chac\'on have recently defined quadratic modular symbols for
the Shimura curves X(D,N) attached to Eichler orders of level N of an
indefinite quaternion rational algebra of discriminant D. In this paper, we
give a cohomological interpretation of these quadratic modular symbols.
Explicit computations for the homology of some Shimura curves are also
provided.
