Temporary inactivation reveals an essential role of the dorsal hippocampus in consolidation of object recognition memory.

The role of the hippocampus in novel object recognition (NOR) memory remains controversial. Here we report the finding that the dorsal hippocampus is essential for consolidation of NOR memory up to 3 h after training. Temporary inactivation of the dorsal hippocampus with a bilateral intrahippocampal infusion of muscimol immediately or 3 h, but not 6 h post-training impaired 24-h NOR retention in male rats. These results strongly indicate that the dorsal hippocampus is required for early and delayed NOR consolidation.