Learning and memory in streptozotocin-induced diabetic rats in a novel spatial/object discrimination task

Diabetes mellitus is associated with disturbances of cognitive functioning. The aim of this study was to examine cognitive functioning in diabetic rat s using the 'Can test', a novel spatial/object learning and memory task, wi thout the use of aversive stimuli. Rats were trained to select a single rew arded can from seven cans. Mild water deprivation provided the motivation t o obtain the reward (0.3 mi of water). After 5 days of baseline training, i n which the rewarded can was marked by its surface and position in an open field, the animals were divided into two groups. Diabetes was induced in on e group, by an intravenous injection of streptozotocin. Retention of baseli ne training was tested at 2-weekly intervals for 10 weeks. Next, two adapte d versions of the task were used, with 4 days of training in each version. The rewarded can was a soft-drink can with coloured print. In a 'simple vis ual task' the soft-drink can was placed among six white cans, whereas in a 'complex visual task' it was placed among six soft-drink cans from differen t brands with distinct prints. In diabetic rats the number of correct respo nses was lower and number of reference and working memory errors higher tha n in controls in the various Versions of the test. Switches between tasks a nd increases in task complexity accentuated the performance deficits, which may reflect an inability of diabetic rats to adapt behavioural strategies to the demands of the tasks. (C) 2001 Elsevier Science B.V. All rights rese rved.