RESEARCH ARTICLE Novel odour recognition memory is independent of the hippocampus in rats Gavin A. Scott • Mbongeni Mtetwa • Hugo Lehmann Received: 3 August 2012 / Accepted: 4 October 2012 / Published online: 26 October 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract We examined the effects of hippocampal (HPC) damage on odour recognition memory, using a novel odour recognition task that was adapted from the more common novel object recognition task. Three sepa- rate experiments were conducted. In Experiment 1, we tested rats in novel odour recognition across different retention intervals (i.e. 15 min, 24 h, 1 week, 5 weeks). Given a single acquisition session, rats’ performance deteriorated after 24 h, but given multiple acquisition sessions (i.e. four sessions over 2 days), rats were able to perform well after retention intervals up to 5 weeks. In Experiment 2, we examined the possible anterograde amnesic effects of HPC damage on novel odour recogni- tion, finding that pre-training damage to the entire HPC failed to cause amnesia for retention delays extending up to 5 weeks. In Experiment 3, we examined whether post- training HPC damage would cause retrograde amnesia, but failed to find any evidence of an impairment. The com- bined results suggest that the neural network supporting odour recognition is independent of the HPC. Keywords Amnesia Á Lesion Á Novelty preference Á Odour Á Hippocampus Á Recognition Á Rat Introduction The hippocampus (HPC) is considered to play an integral role in recognition memory (Manns et al. 2003; Rosen- baum et al. 2005), which is the ability to identify stimuli that have been previously encountered. For instance, Reed and Squire (1997) found that patients with damage to the HPC were impaired in a delayed non-matching-to-sample task. Specifically, the patients were unable to correctly identify the object within a pair they had seen as early as 5 min prior. Supporting the patient findings, recognition memory impairments following HPC damage have also been reported in non-human animals such as monkeys and rats (Mahut et al. 1982; Clark et al. 2000, 2001; Gaskin et al. 2003; Broadbent et al. 2010). However, there is still debate on the specific contribution of the HPC versus other medial temporal lobe structures in recognition memory (see Winters et al. 2008, 2010; Clark and Squire 2010). A common behavioural task for testing recognition memory in rats is novel object recognition, which relies on the innate propensity of rats to spend a greater amount of time investigating a novel object over a familiar one (Ennaceur and Delacour 1988). The task typically involves presenting rats with two identical objects in a small open field. After being allowed to investigate the objects for a given period, the rats are removed from the apparatus for a retention interval before being returned to the apparatus for the recognition test. During this test phase, the rats are now presented with a copy of the object they previously encountered (i.e. familiar) and an object they never encountered before (i.e. novel). The rats will investigate the novel object more than the familiar object, suggesting that they recognize the familiar object. In rats, damage to the HPC after training (post-training) causes retrograde amnesia for novel object recognition, suggesting that the HPC plays an important role for this type of memory (Gaskin et al. 2003; Broadbent et al. 2010). Interestingly, however, damage to the HPC prior to training (pre-train- ing) causes little to no anterograde amnesia in this task (Mumby et al. 2002; Gaskin et al. 2003; Mumby et al. G. A. Scott Á M. Mtetwa Á H. Lehmann (&) Psychology Department, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 7B8, Canada e-mail: hugolehmann@trentu.ca 123 Exp Brain Res (2013) 224:199–209 DOI 10.1007/s00221-012-3304-4