  Collective monopole vibrations are studied in the framework of an
antisymmetrized version of molecular dynamics as a function of the vibration
amplitude. The giant monopole resonance energy in ${}^{40}Ca$ is sensitive to
the incompressibility of the effective interaction, in good agreement with
complete time-dependent Hartree-Fock calculations. The collective response of
${}^{12}C$, ${}^{16}O$ and ${}^{24}Mg$ is also studied. For these lighter
nuclei that have an important contribution of an $\alpha$-clustered component,
different frequencies are observed, corresponding to two different types of
vibrations associated with breathing and moving of the underlying clusters.
Possible connections with direct breakup into $\alpha$ clusters at high
excitation energy are discussed.
