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J H Freeman

Publications and source records attributed to J H Freeman.

4 recordsLinked to original sources
PubMed1992

Eyeblink conditioning in the developing rat.

Long-Evans rat pups, 17-18 or 24 days of age, were trained with an eyeblink conditioning (EBC) procedure that was used previously with adult rats (Skelton, 1988). Pups received 3 sessions of delay conditioning in a single day at about 4-hr intervals (100 trials/session). Trials involved pairings of an auditory conditioned stimulus (2.8-kHz, 82-dB tone) and a periocular-shock unconditioned stimulus (US; 100 ms, 2 mA), which were presented 280 ms apart. EBC was observed at both ages, but older pups learned much more rapidly. Subsequent experiments established that this effect is associative (Experiment 2), that age differences in EBC cannot be attributed to differences in ability to respond or in sensitivity to the US (Experiment 3), and that EBC rate can be modulated by motivational state (Experiment 4). This preparation may help elucidate the relation between neural development and the ontogeny of learning.

Aging↗
PubMed1992

Medial prefrontal cortex lesions and spatial delayed alternation in the developing rat: recovery or sparing?

In Experiment 1, Long-Evans rat pups received medial prefrontal cortex (PFC) aspirations or sham surgery on Postnatal Day 10 (PND10) and were then trained on PND23 to perform one of two T-maze tasks: discrete-trials delayed alternation (DA) or simple position discrimination. Early PFC damage produced a selective failure to learn the DA task. In Experiment 2, pups given the same lesion or sham surgery were trained on DA on PND19, PND27, or PND33. In relation to sham-operated controls, pups with PFC damage were impaired on PND19, somewhat impaired on PND27, and entirely unimpaired when tested on PND33. In Experiment 3, pups given larger lesions of the frontal cortex on PND10 were impaired on DA when tested on PND23 but not when tested on PND33. These findings indicate that early PFC lesions result in a memory deficit around the time of weaning, which then recovers over the next 10-14 days of development. Moreover, the early deficit is selective for a late developing cognitive process (or processes) that is involved in acquisition of DA.

Aging↗
PubMed1991

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

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.

Animals↗