Journal of Neuroscience, Vol 16, 2780-2787, Copyright © 1996 by Society for Neuroscience
The hippocampus and long-term object memory in the rat
N Vnek and LA Rothblat
Department of Psychology, George Washington University, Washington, DC 20052, USA.
Animal models of amnesia have yielded many insights into the neural
substrates of different types of memories. Some very important aspects of
memory, however, have been ignored in research using experimental animals.
For example, to examine long-term memory investigators traditionally have
relied on measures of information acquisition, which stand in contrast to
the measures of retention commonly used in work with humans. We have
recently developed a behavioral paradigm that measures both the acquisition
and long-term retention of object discriminations, and found a selective
retention impairment in rats with entorhinal-hippocampal disconnection
(Vnek et al., 1995). The present study was designed to determine whether
direct damage to the hippocampus likewise would lead to a selective deficit
in the retention of visual discriminations. Rats with aspiration lesions of
the dorsal hippocampus, rats with neocortical control lesions, and normal
controls were trained on three object discrimination problems and then
retrained 3 weeks later to measure retention. All animals showed the same
level of performance during the training (acquisition) phase of testing,
but the performance of animals with dorsal hippocampal injury fell below
that of controls during retraining (retention). Taken together, these and
our earlier results suggest that the hippocampus and anatomically related
structures are particularly important for retaining visual discriminations
over long delay intervals. These findings may clarify the role of the
hippocampus in nonspatial memory.