Trial-unique, delayed nonmatching-to-location (TUNL): A novel, highly hippocampus-dependent automated touchscreen test of location memory and pattern separation

• Published in: Neurobiology of learning and memory Vol. 94; no. 3; pp. 341 - 352
• Main Authors: Talpos, J.C., McTighe, S.M., Dias, R., Saksida, L.M., Bussey, T.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.10.2010; Elsevier; Elsevier BV; Academic Press
• Subjects: Analysis of Variance; Animal behavior; Animal memory; Animal models; Animals; Automated; Behavioral psychophysiology; Biological and medical sciences; Delayed nonmatch-to-position; Fundamental and applied biological sciences. Psychology; High-throughput; Hippocampus; Hippocampus - physiology; Male; Memory - physiology; Neurobiology; Pattern Recognition, Visual - physiology; Pattern separation; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rodents; Space Perception - physiology; Spatial learning; High-throughput; Automated; Delayed nonmatch-to-position; Pattern separation; Hippocampus; Spatial learning; Central nervous system; Space perception; Encephalon; Touch screen; Acquisition process; Perceptive learning; Spatial memory
• DOI: 10.1016/j.nlm.2010.07.006
• ISSN: 1074-7427

► TUNL can be used to study spatial working memory or spatial pattern separation. ► TUNL likely has fewer mediating strategies then other DNMTP tasks. ► TUNL is highly sensitive to the delay-dependent effects of hippocampal lesions. The hippocampus is known to be important for learning and memory, and is implicated in many neurodegenerative diseases. Accordingly many animal models of learning and memory focus on hippocampus-dependent tests of location learning and memory. These tests often use dry mazes or water mazes; however automated testing in operant chambers confers many advantages over such methods. Some automated tests of location memory, such as delayed nonmatching-to-position (DNMTP) have, however, fallen out of favor following the discovery that such tasks can be solved using mediating behaviors that can bridge the delay and reduce the requirement for memory per se. Furthermore some researchers report that DNMTP performance may not always require the hippocampus. Thus, in an attempt to develop a highly hippocampus-dependent automated test of location memory that elicits fewer mediating behaviors, we have developed a trial-unique nonmatching-to-location (TUNL) task, carried out in a computer-automated touchscreen testing apparatus. To test the efficacy of this assay, rats with lesions to the hippocampus, or a sham lesion control group, were tested under a variety of conditions. Both groups were able to perform well at a delay of 1s, but the lesion group was highly impaired when tested at a 6s delay. Moreover, animals with lesions of the hippocampus showed a greater impairment when the distance between the locations was reduced. This result indicates that TUNL can be used to investigate both memory across a delay, and spatial pattern separation (the ability to disambiguate similar spatial locations). Performance-enhancing mediating behaviors during the task were found to be minimal. Thus, the TUNL task has the potential to serve as a powerful tool for the study of the neurobiology of learning and memory.