Assessment of disease-related cognitive impairments using the novel object recognition (NOR) task in rodents

The novel object recognition test (NOR) test is a two trial cognitive paradigm that assesses recognition memory. Recognition memory is disturbed in a range of human disorders and NOR is widely used in rodents for investigating deficits in a variety of animal models of human conditions where cognition is impaired. It possesses several advantages over more complex tasks that involve lengthy training procedures and/or food or water deprivation. It is quick to administer, non-rewarded, provides data quickly, cost effective and most importantly, ethologically relevant as it relies on the animal's natural preference for novelty. A PubMed search revealed over 900 publications in rats and mice using this task over the past 3 years with 34 reviews in the past 10 years, demonstrating its increasing popularity with neuroscientists. Although it is widely used in many disparate areas of research, no articles have systematically examined this to date, which is the subject of our review. We reveal that NOR may be used to study recognition memory deficits that occur in Alzheimer's disease and schizophrenia, where research is extensive, in Parkinson's disease and Autism Spectrum Disorders (ASD) where we observed markedly reduced numbers of publications. In addition, we review the use of NOR to study cognitive deficits induced by traumatic brain injury and cancer chemotherapy, not disorders per se, but situations in which cognitive deficits dramatically reduce the quality of life for those affected, see Fig. 1 for a summary. Our review reveals that, in all these animal models, the NOR test is extremely useful for identification of the cognitive deficits observed, their neural basis, and for testing the efficacy of novel therapeutic agents. Our conclusion is that NOR is of considerable value for cognitive researchers of all disciplines and we anticipate that its use will continue to increase due to its versatility and several other advantages, as detailed in this review.