  We suggest that physics underlying the recently observed removal of
sublattice and spin degeneracies in graphene in a strong magnetic field
describes a phase transition connected with the generation of excitonic and
spin gaps. The strong-coupling regime is described using a phenomenological
model with enhanced Zeeman splitting (spin gap) and excitonic gaps. The
experimental form of the Hall conductivity $\sigma_{xy}$ with the additional
$\nu= 0, \pm 1$ plateaus is reproduced. The form of $\sigma_{xy}$ in the case
of a strong-coupling regime with no enhanced Zeeman splitting is also
discussed.
