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Individual variation in the spatial reference and working memory assessed under allothetic and idiothetic orientation cues in rat

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Jakubowska-Dogru E., Gumutbat U., Kara F.

Acta Neurobiologiae Experimentalis

2003

vol. 63

issue 1

17-23

The present study was designed to examine which kind of memory: reference or working, better correlates with individual variation in rats? spatial learning abilities. To answer this question two groups of rats were trained to an arbitrary criterion in a partially baited 12-arm radial maze under two different experimental conditions: with or without allothetic cues. After 10 days break, rats were examined under the same conditions for memory retention. Within- and between-group variation in the length of training to criterion, and in the frequency of reference and working memory errors were analysed. The present experiment confirmed the facilitating effect of the presence of distal visual cues on place learning in rats. Task-dependent (between-group) differences in the rate of learning were attributed to differences in the frequency of reference memory errors. Conversely, within-group variation in the rate of task acquisition reflected individual variation in the frequency of working memory errors. These results were looked upon from an evolutionary perspective. Low correlation between reference and working memory errors confirms that these two types of memory have different mechanisms. The fact that differences in the rate of learning were not paralleled by the differences in the memory retention supports the notion that memory acquisition and memory retention are two independent processes.

Ranking of memories and behavioral strategies in the radial maze

100%

Stolberg A.

Acta Neurobiologiae Experimentalis

2005

vol. 65

issue 1

39-49

New features of actual choice behavior and effortful information processing in rats were demonstrated in an eight-arm radial maze through modifications of a matching-to-sample task. Two attempts were allowed for a squad of hooded Sprague-Dawley rats (n=7) for finding a reward in a testing phase of the task. The results showed flexibility and sooner learning to matching rule on the second testing attempt that was only later followed by an improvement of choice accuracy on the first attempt. 'Hidden learning' on the second attempt could reflect memories and behavioral strategy, which were present, but not expressed on the first choice. The hypothesis was advanced that learning expressed on the second attempt reflects encoding of a matching rule, whereas improvement on the first choice reflects changes in the rank of acquired memories and behavioral strategy. A second experiment on the same squad of rats tested the ability of trained animals to rank already acquired memories. Following the introduction of the second sample to the study phase of the task, the rats learned to prefer to match the first sample in the testing phase, rearranging ranks of stored memories under the internal control of win?stay strategy. Alternative explanations of interference, trace decay and ranking were compared in order to account for the present results.

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2 Acta Neurobiologiae Experimentalis

1 2005

1 2003

1 Gumutbat U.

1 Jakubowska-Dogru E.

1 Kara F.

1 Stolberg A.

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Individual variation in the spatial reference and working memory assessed under allothetic and idiothetic orientation cues in rat

Ranking of memories and behavioral strategies in the radial maze