Biomedical subjects

P Jackson-Smith

Publications and source records attributed to P Jackson-Smith.

4 recordsLinked to original sources

PubMed1997

Impaired place learning and unimpaired cue learning in hippocampal-lesioned pigeons.

Hippocampal processing is often crucial for normal spatial learning and memory in both birds and mammals, suggesting a general similarity in avian and mammalian hippocampal function. However, few studies using birds have examined the effect of hippocampal lesions on spatial tasks analogous to those typically used with mammals. Therefore, we examined how hippocampal lesions would affect the performance of pigeons in a dry version of the water maze. Experiment 1 showed that hippocampal-lesioned birds were impaired in acquiring the location of hidden food in the maze. Experiment 2 showed that hippocampal-lesioned birds were not impaired when a single cue indicated the location of hidden food. These results support the notion that avian and mammalian hippocampal functions are quite similar, in terms of the tasks for which their processing is crucial and the tasks for which it is not.

Animals↗

PubMed1995

Effects of ibogaine on sensory-motor function, activity, and spatial learning in rats.

Ibogaine, a naturally occurring alkaloid, has been show to reduce naloxone-precipitated withdrawal symptoms from morphine. Given the clinical possibilities, it is important to determine ibogaine's effects on sensory-motor function, activity, learning, and memory. Long-Evans rats injected with doses of 20-60 mg/kg of ibogaine displayed slower response times on sensory and sensory-motor tests and were impaired in performing specific motor reflexes at doses of 40-60 mg/kg. Furthermore, these rats showed a marked reduction in locomotor and nonlocomotor activity, as well as emotionality at doses ranging from 10-40 mg/kg. At the higher doses the rats appeared to be virtually inactive. There were also deficits in learning a spatial location task (a dry-land version of the Morris water-maze). The deficits, however, were probably due to a reduction in locomotor activity and reduction in detection of sensory information. In a final experiment, a single injection of 40 mg/kg of ibogaine had marked deleterious effects on the acquisition of the spatial location task 1 but not 7 days after the injection, even though in this case there were no effects on sensory motor function 1 or 7 days after the injection. Thus, there are severe sensory-motor activity and learning problems while the animal is under the influence of ibogaine (acute effect) as well as long-term consequences on learning without concomitant changes in sensory-motor function.

Animals↗

PubMed1993

Continuous recognition of spatial and nonspatial stimuli in hippocampal-lesioned rats.

The present experiments compared the performance of hippocampal-lesioned rats to control rats on a spatial continuous recognition task and an analogous nonspatial task with similar processing demands. Daily sessions for Experiment 1 involved sequential presentation of individual arms on a 12-arm radial maze. Each arm contained a Froot Loop reinforcement the first time it was presented, and latency to traverse the arm was measured. A subset of the arms were repeated, but did not contain reinforcement. Repeated arms were presented with lags ranging from 0 to 6 (0 to 6 different arm presentations occurred between the first and the repeated presentation). Difference scores were computed by subtracting the latency on first presentations from the latency on repeated presentations, and these scores were high in all rats prior to surgery, with a decreasing function across lag. There were no differences in performance following cortical control or sham surgery. However, there was a total deficit in performance following large electrolytic lesions of the hippocampus. The second experiment employed the same continuous recognition memory procedure, but used three-dimensional visual objects (toys, junk items, etc., in various shapes, sizes, and textures) as stimuli on a flat runway. As in Experiment 1, the stimuli were presented successively and latency to run to and move the object was measured. Objects were repeated with lags ranging from 0 to 4. Performance on this task following surgery did not differ from performance prior to surgery for either the control group or the hippocampal lesion group. These results provide support for Kesner's attribute model of hippocampal function in that the hippocampus is assumed to mediate data-based memory for spatial locations, but not three-dimensional visual objects.

Animals↗

PubMed1986

Categorical shape and color coding by pigeons.

Categorical coding is the tendency to respond similarly to discriminated stimuli. Past research indicates that pigeons can categorize colors according to at least three spectral regions. Two present experiments assessed the categorical coding of shapes and the existence of a higher order color category (all colors). Pigeons were trained on two independent tasks (matching-to-sample, and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials one of the two comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the two stimuli from the other task was introduced suggested categorical coding rules. In Experiment 1 evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Experiment 2 replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Overall, the results indicate that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical.

Animals↗