  The low-lying spectra of $^{24,25,26}{\rm Ne}$ and the structure of the pygmy
dipole resonance (PDR) in $^{26}{\rm Ne}$ have been theoretically studied by
the antisymmetrized molecular dynamics (AMD) and its extended version called
shifted-basis AMD. The calculated energy and strength of the PDR reasonably
agree with the observation, and the analysis of the wave function shows that
the PDR is dominated by neutron excitation coupled to the quadrupole excited
core nucleus $^{25}{\rm Ne}$, which explains the observed unexpected decay of
PDR to the excited states of $^{25}{\rm Ne}$. The large isoscalar component of
PDR is also shown and the enhancement of the core excitation in neutron-rich Ne
isotopes is conjectured.
