  We investigate non-extremal D-instantons in an asymptotically $ AdS_5 \times
S^5$ background and the role they play in the $ AdS_5 / CFT_4$ correspondence.
We find that the holographic dual operators of non-extremal D-instanton
configurations do not correspond to self-dual Yang-Mills instantons, and we
compute explicitly the deviation from self-duality. Furthermore, a class of
non-extremal D-instantons yield Euclidean axionic wormhole solutions with two
asymptotic boundaries. After Wick rotating, this provides a playground for
investigating holography in the presence of cosmological singularities in a
closed universe.
