Fornix transections disrupt the ontogeny of latent inhibition in the rat

Self Cite

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 (DA) or a simple position discrimination (PD) task in a T maze. Rat pups in both surgical conditions learned the PD task within five 12-trial blocks of training. However, only sham-operated pups learned the DA task. In Experiment 2, performance of DA emerged between PND19 and PND27 in sham-operated pups but failed entirely to develop in pups with early lesions. In Experiment 3, fornix-transected pups that were given extended DA training (132 trials) on PND23-PND24 showed some improvement in performance but remained impaired in relation to sham-operated controls. These findings implicate the limbic system in the postnatal development of DA but not PD and suggest that dual-process theories of memory may be relevant to the psychobiology of cognitive development.

Section: Sham Lesionsupporting

confidence: 85%

Fimbria-fornix transections disrupt the ontogeny of delayed alternation but not position discrimination in the rat.

Freeman¹,

Stanton²

1991

Self Cite

“…Some reports have suggested, though, that preexposures may have the reverse effect of facilitating conditioning in younger animals (Kucharski & Spear, 1985). The later emergence of inhibitory effects may be related to the delayed maturation of forebrain structures, such as the hippocampus, that are believed to play a central role in processing the configural properties of sensory stimuli during conditioning (Nicolle, Barry, Veronesi, & Stanton, 1989). The facilitatory preexposure effects in the fetal rat suggest that the hippocampus and cortical structures that show only rudimentary development by E20 of gestation are likely to play little or no role in the acquisition or expression of conditioned opioid responses or in the effects of CS preexposure in the rat fetus.…”

Section: Discussionmentioning

confidence: 99%

Stimulus contingencies that permit classical conditioning of opioid activity in the rat fetus.

Robinson¹,

Smotherman²

1997

In a prenatal model of classical conditioning, rat fetuses received presentations of an artificial nipple (conditioned stimulus; CS) paired with milk (unconditioned stimulus). Infusion of milk promotes activity in the kappa opioid system of the fetus, but after 2, 3, or 6 pairings with the artificial nipple, milk evoked both kappa and mu opioid activity. The nipple CS has no effect on opioid activity, but after pairing with milk evoked a mu opioid response. Conditioned mu opioid activity was evident in 60% of subjects tested after 1 paired conditioning trial. Significantly more fetal subjects (90%) exhibited conditioned opioid activity if preexposed to the nipple twice before conditioning. CS preexposure altered behavior during the conditioning trial, with preexposed fetuses showing more pronounced responses to milk infusion. Exposure to familiar stimuli facilitates classical conditioning of physiological responses, including opioid activity, during the first suckling episode.

“…A conventional latent inhibition paradigm with four preexposures to the to-be-conditioned taste and one-bottle test was used by Nicolle et al (1989) to study the ontogenetic development of latent inhibition in taste aversion learning. They showed that fornix transections in 18-day-old rats interfered with the normal appearance of the effect by 32 days after birth.…”

Section: Methodsmentioning

confidence: 99%

Dorsal hippocampal lesions impair blocking but not latent inhibition of taste aversion learning in rats.

Gallo

Cândido²

1995

The aim of the present experiments was to study the effect of nonselective electrolytic lesions of the rat dorsal hippocampus on 2 learning phenomena: the L.J. Kamin (1969) blocking effect and latent inhibition of taste aversion learning. Bilateral dorsal hippocampal lesions selectively impaired blocking induced by 1 saccharin-lithium chloride pairing previous to 1 serial compound (saccharin-cider vinegar)-lithium pairing, but lesions had no effect on latent inhibition of a saline aversion, induced by 6 saline preexposures, in the same group of animals. Moreover, dorsal hippocampal lesions did not affect latent inhibition of saccharin-conditioned aversion induced by 1 or 6 preexposures. It is argued that blocking and latent inhibition of taste aversion learning do not share a common neural mechanism.