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FIMBRIA-FORNIX TRANSECTIONS DISRUPT THE ONTOGENY OF DELAYED ALTERNATION BUT NOT POSITION DISCRIMINATION IN THE RAT
Citation:
Freeman, J. AND M. Stanton. FIMBRIA-FORNIX TRANSECTIONS DISRUPT THE ONTOGENY OF DELAYED ALTERNATION BUT NOT POSITION DISCRIMINATION IN THE RAT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-91/160 (NTIS PB91231282), 1991.
Description:
In Experiment 1, Long-Evans rat pups received fimbria-fornix transections or sham surgery on postnatal day 10 (PND10) and were then trained on PND23 to perform either a discrete-trials delayed alternation or a simple position discrimination (position habit) in a T-maze. at pups in both surgery conditions learned to perform the position habit task at a 90-95% level within five 12-trial blocks of training. owever, only sham-operated pups were able to learn the delayed alternation task. imbria-fornix transected pups failed to improve their performance across the training blocks. n Experiment 2, pups subjected to the same lesion or sham surgery were trained on delayed alternation on either PND19 or PND27. erformance on this task improved with increasing age in sham-operated pups but failed entirely to develop in fimbria-fornix transected pups. xperiment 3 showed that if extended training (132 trials) on the delayed alternation task was given on PND23-24, fornix-transected pups show some improvement in performance but remain impaired relative to sham-operated controls. hese findings indicate that early damage to the limbic system disrupts maturation of a late-developing memory process (or processes) that is involved in acquisition of delayed alternation. his disruption is selective because acquisition of the position habit, a task which can be learned at very early stages of development, was not prevented by the early lesion. hese findings are consistent with dual-process theories of memory and suggest that such theories may be relevant to the psychobiology of cognitive development.