Jj. Bolhuis et al., RETROGRADE-AMNESIA AND MEMORY REACTIVATION IN RATS WITH IBOTENATE LESIONS TO THE HIPPOCAMPUS OR SUBICULUM, The Quarterly journal of experimental psychology. B, Comparative andphysiological psychology, 47(2), 1994, pp. 129-150
The retrograde effects of hippocampal lesions on spatial memory were s
tudied. Rats were given a series of 48 place-navigation trials in an o
pen-field water-maze followed, either 3 days or 14 weeks later, by ibo
tenic acid lesions of the hippocampus (HPC) or subiculum (SUB), or by
sham-surgery (SHAM). Two weeks after surgery they were given a retenti
on test without a hidden escape platform. There was a significant decl
ine in performance with time in the SHAM group, but with the 14-week S
HAM group performing significantly better than chance levels, whereas
both lesioned groups performed at chance at both retention intervals.
All Tats were then retrained for 24 trials. SHAM rats escaped rapidly
within 2 trials, suggesting a reactivation of memory rather than relea
rning. The HPC groups were severely impaired during retraining, with a
developing trend towards better performance in the 3-day group. After
24 trials of training with the escape platform placed in the opposite
quadrant of the pool, this new location was learned successfully by S
HAm and SUB rats, but not by Hpc rats. These results indicate that sel
ective hippocampal formation lesions can cause deficits in retrieval b
ut do not reveal a time-dependent gradient of memory consolidation.