Donald M Wilkie

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The present experiments investigated the effects of pregnancy on performance in the Morris water maze and on hippocampal volume. In the first study, pregnant rats (in between the first and second trimester) outperformed nonpregnant rats on the Morris water maze on 1 day of testing. In the second study, rats were tested in a working memory variation of the(More)
Rats received 2 daily sessions in a large clear chamber. A lever was mounted on each of the 4 chamber walls. For each rat, a different lever provided food during 0930 and 1530 sessions. The rats learned which lever would provide food at 0930 and 1530. Probe tests suggested that the rats learned to press 1 lever during their 1st session of each day and to(More)
We have collected evidence that a hoarding species of rodent, the Syrian golden hamster (Mesocricetus auratus), uses spatial memory in foraging for food to hoard. Before each trial, we baited the same four arms of a modified seven arm radial maze with sunflower seeds. During the trial we gave each hamster 15-min access to the maze and observed its(More)
There is an apparent discrepancy between the widespread view that backward conditioning does not occur and the experimental evidence which suggests that it does. Backward pairing of conditioned and unconditioned stimuli frequently has resulted in effects similar to those produced by forward pairing, and the results of several recent experiments have(More)
Repeated pairing of the onset of a stationary light (CS) that signalled electrical stimulation of brain-stimulation reward sites in the mesencephalon (US) resulted in autoshaped approach behavior to the CS. After acquisition of approach to the CS two groups of rats were injected with either pimozide (0.15, 0.50, or 1.0 mg/kg) or haloperidol (0.05, 0.10, or(More)
The efficacy of synaptic transmission from the perforant path (PP) to the granule cells in the dentate gyrus (DG) of freely moving rats was monitored electrophysiologically over the course of training in an appetitively motivated, discriminated operant paradigm. Every day, 22 hr after behavioral sessions, evoked potentials were recorded from the DG(More)
Superior colliculus lesions generally result in a deficit in visual orienting described as sensory neglect. This observation was confirmed in this study: Rats with lesions did not orient to some stimuli that intact rats readily oriented to. However, rats with lesions did orient to stimuli that the intact rats treated as more salient. Also, when the less(More)
On daily time-place learning tasks animals can work for food at different spatial locations during sessions at different times of the day. In previous experiments rats tracked this pattern of food availability with ordinal timing-they learned to respond at the locations in the correct order each day. In contrast, pigeons used circadian timing. In this(More)
Pigeons received discrimination training in which food reinforcement for key pecking was conditional upon both spatial and temporal cues. In Experiment 1 food was available for periods of 15 min at each of four locations (pecking keys) during a 60-min trial. However, unlike the procedures used in a previous experiment (Wilkie and Willson, 1992, Experiment(More)
Because the presence or absence of memories in the brain cannot be directly observed, scientists must rely on indirect measures and use inferential reasoning to make statements about the status of memories. In humans, memories are often accessed through spoken or written language. In animals, memory is accessed through overt behaviours such as running down(More)