Spatial learning and memory differs between single and cohabitated guinea pigs

In socially-living animals, social enrichment enhances spatial learning and memory while separation from conspecifics can severely impair these abilities. In the present work, guinea pigs were kept in isolation or cohabitated in heterosexual pairs and then subjected to a labyrinth task. Latency-time to bait, error-rate, amount of movement and pre- and post-experimental cortisol (CORT) were registered. During a 5d-acquisition phase, single animals (N=19) showed a more efficient encoding of spatial information, with significantly decreased latency-time and error-rate over the time course. In contrast, cohabitated animals (N=19) did not show a significant improvement. Three days after acquisition, memory was tested in a retention test, under the same conditions. With regard to behavioral performance, there was no significant difference between cohabitated and single animals. Pre-experimental CORT was significantly higher in cohabitated animals when compared to single ones. Post-experimentally, CORT increased significantly in singles but not in cohabitated animals when compared to pre-experimental values. Thus, both groups did not differ from each other at that point. Social condition seemed to be an important modulator, in that learning and memory were more impaired in paired animals than in single ones. The failure of cohabitated animals to encode spatial memory more quickly may have been caused by a more chronically up-regulated HPA-axis. The post-experimental CORT increase of singles may be due to more efficient handling of short-term stress exposure.