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Biomedical subjects

P Ellen

Publications and source records attributed to P Ellen.

At least 19 recordsLinked to original sources
PubMed1986

Cholinergic blockade effects on spatial integration versus cue discrimination performance.

A within-subjects investigation was conducted to determine the effects of central versus peripheral cholinergic blockade in animals tested either on a spatial integration task in which the possibility of rule learning was also available or on a visual discrimination task in which the daily location of food was marked by a distinctive visual stimulus pattern. All testing was conducted on the Maier three-table apparatus. It was found that the only effect of the peripheral cholinergic blockade on the performance of either task group was to produce a decrease in exploratory behavior. In contrast, central cholinergic blockade markedly impaired spatial integration performance; however, it did not impair the ability of animals in rule learning or visual discrimination learning. It was also found that central cholinergic blockade impaired the animal's tendency to enter all tables before reentering a given table during the exploratory phase of the daily session. This finding was interpreted as reflecting an impairment of working memory for spatial information, rather than a general impairment in working memory, and this interpretation was applied to the explanation of the deficit in the spatial integration performance.

Animals↗
PubMed1985

Spatial problem solving in a dual runway task by normal and septal rats.

The addition of a dual runway configuration did not disrupt the successful performance of normal animals, nor did it improve the deficit of septal rats on the Maier three-table spatial integration task. Both groups of animals displayed a preference for the outside runway configuration during exploration. During testing, however, septal animals retained this preference, whereas normal subjects attempted solution by using the inside runway configuration. This fact, in addition to the apparent lack of a habituation pattern during exploration, suggests that septal animals do not acquire a spatial representation of the test situation. It is suggested that the inability of septal rats in spatial situations is due to an inability to form rather than an inability to use spatial maps.

Animals↗
PubMed1979

Performance of rats on the Maier three-table task following septal lesions occurring 24 hours after birth.

The purpose of this study was to determine whether behavioral sparing would be demonstrated when septal lesions occurred prior to the age at which the tested behavior first appears in normal rats. Rats given septal lesions at 1 day or 7 days after birth performed at approximately chance on the Maier three-table task when tested at 90 days of age. Rats that had control electrode insertions at the same ages performed at a level similar to normal animals. Animals given septal lesions at either age explored significantly more than did control animals. Results are discussed in terms of the constancy over time of the septal contribution to performance on the three-table task and the involvement of the septum and hippocampus in the processing of spatial information.

Age Factors↗
PubMed1978

Medial septal lesions: disruptions of microregulatory patterns and circadian rhythmicity in rats.

The microregulatory patterns of food and water intake were examined in male and female rats bearing medical septal lesions and in sham-operated controls. Medial septal ablation, although not affecting the total amount of food or water ingested, resulted in a profound disruption of the pattern of intake. Circadian rhythmicity was disrupted for a period, returning to normal by 25 days postlesion. Permanent disruptions occurred in feeding patterns in the rats with septal lesions ingested more frequent but smaller meals. There was also a marked increase in food-intake-associated drinking and a decrease in non-food-intake-associated drinking. The results are interpreted to reflect two separate independent effects, a general circadian disruption and an alteration in requlatory behavior produced by a chronic depletion of body fluid.

Animals↗
PubMed1978

Response suppression on DRL by rats with septal damage.

The effectiveness of the differential reinforcement for low rates of responding (DRL) contingency in suppressing response rates of septal rats was investigated by using a Multi-DRL-yoked-VI (variable interval) schedule of reinforcement. The yoking procedure equated the interreinforcement times on the two schedules. Each schedule was in effect for half of each session, and the change in schedule was signaled by the presence or absence of a cue light. Schedule order and DRL delay requirement were varied. For both normal and septal rats, the response rates were higher in the VI component than the DRL component; this effect demonstrates that the responding of septals as well as normals is suppressed by the differential reinforcement of a particular class of IRTs. A sharp difference in the level of responding occurred at the point of transition from one component of the multiple schedule to the other, which provides evidence of a discrimination between the two schedules for both normals and septals. The conclusion is that the responding of septals is suppressed by the DRL contingency and not controlled solely by the density and distribution of reinforcement.

Animals↗
PubMed1977

Influence of neonatal septal lesions on DRL performance in adulthood.

Two experiments are reported describing the influence of neonatal septal lesions on responding of rats trained on a differential-reinforcement-of-low-rate (DRL) schedule in adulthood. Rats given septal lesions at 1 day or at 7 days after birth emitted a significantly higher number of responses and earned fewer reinforcements than did animals given control electrode insertions. Thus, the inefficient performance on the DRL schedule, often observed after septal lesions in adulthood, does not depend upon the age of the animal at the time of the lesion. Furthermore, operant training given at an early age (25-45 days) to animals with neonatal septal damage did not facilitate performance when the animals were retrained in adulthood. In short, septal lesions at any age lead to permanent impairments of performance on a DRL 20-sec reinforcement schedule.

Age Factors↗
PubMed1976

Cued DRL training: effects on the permanence of lesion-induced overresponding.

The purpose of the present study was to determine the degree to which lesions in the septum and other anatomically related structures result in the presence and/or permanence of an overresponding symptom on a differential-reinforcement-of-low-rate (DRL 20 sec) schedule. Animals were given 15 days of training to determine the presence or absence of overresponding. Then, animals that overresponded were divided into two groups, with one receiving 15 days of cued DRL training and 15 days of regular DRL training while the other received 30 days of regular DRL training. Overresponding occurred following lesions in septum, hippocampus, medialis dorsalis, and ventral thalamus pars dorsalis. While in effect, cued DRL facilitated performance in controls and in operated animals but did not facilitate performance following its removal in septals. Although the hippocampals continued to overrespond with extended training on a regular DRL schedule, exposure to the cued DRL allowed hippocampals to reduce responding and increase the frequency of obtained reinforcements. Lesions in medialis dorsalis and ventral thalamus led to an overresponding that disappeared with prolonged regular DRL training. Finally, it was shown that the cued DRL training actually functioned as a time-out from DRL training. The variations in the permanence of the overresponding symptom according to lesion locus preclude the identification of the lesion-induced dysfunction based solely on the presence or absence of overresponding.

Animals↗
PubMed1975

Cholinergic blockade, septal lesions, and DRL performance in the rat.

Four experiments describing the effects of cholinergic blockade produced by systemic injection of either atropine sulfate or atropine methyl nitrate on the differential reinforcement of low rate (DRL) responding of rats are reported. It was shown that atropine sulfate injected either chronically or at high dosage suppressed DRL responding. Injected acutely, atropine sulfate produced disinhibitory effects. When atropine was injected either chronically or acutely into animals with septal lesions, there was suppression of responding. It was suggested that the specific behavioral outcome resulting from cholinergic blockade depends on the balance resulting from the competing peripheral and central effects of such blockade.

Animals↗
PubMed1975

Effects of prefeeding on the DRL preformance of rats with septal lesions.

Two experiments reported the effects of prefeeding normal and septal rats prior to their daily sessions on a differential reinforcement of low rates (DRL-20) schedule. Prefeeding reduced responses and increased reinforcements in the case of septal animals, regardless of the level of body weight. In the case of normal animals, prefeeding led to a decrease in responding and an increase in the number of reinforcements obtained only when the animals were at 85% of ad-lib levels, prefeeding, although it decreased responding, also decreased the frequency of obtained reinforcements. These results implied an impairment in normal animals in the discrimination of response feedback by stimulation arising from stomach distention.

Animals↗