title: Object recognition memory in zebrafish.
abstract: The novel object recognition, or novel-object preference (NOP) test is employed to assess recognition memory in a variety of organisms. The subject is exposed to two identical objects, then after a delay, it is placed back in the original environment containing one of the original objects and a novel object. If the subject spends more time exploring one object, this can be interpreted as memory retention. To date, this test has not been fully explored in zebrafish (Danio rerio). Zebrafish possess recognition memory for simple 2- and 3-dimensional geometrical shapes, yet it is unknown if this translates to complex 3-dimensional objects. In this study we evaluated recognition memory in zebrafish using complex objects of different sizes. Contrary to rodents, zebrafish preferentially explored familiar over novel objects. Familiarity preference disappeared after delays of 5 mins. Leopard danios, another strain of D. rerio, also preferred the familiar object after a 1 min delay. Object preference could be re-established in zebra danios by administration of nicotine tartrate salt (50mg/L) prior to stimuli presentation, suggesting a memory-enhancing effect of nicotine. Additionally, exploration biases were present only when the objects were of intermediate size (2 × 5 cm). Our results demonstrate zebra and leopard danios have recognition memory, and that low nicotine doses can improve this memory type in zebra danios. However, exploration biases, from which memory is inferred, depend on object size. These findings suggest zebrafish ecology might influence object preference, as zebrafish neophobia could reflect natural anti-predatory behaviour.
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada; Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB T6G 2G4, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
authors.forename: Zacnicte
authors.initials: Z
authors.lastname: May
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Morrill
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Holcombe
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada.
authors.forename: Travis
authors.initials: T
authors.lastname: Johnston
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Gallup
authors.affiliation: Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB T6G 2G4, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
authors.forename: Karim
authors.initials: K
authors.lastname: Fouad
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada.
authors.forename: Melike
authors.initials: M
authors.lastname: Schalomon
authors.affiliation: Department of Psychology, MacEwan University, Edmonton, AB T5J 4S2, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada,. Electronic address: trevorjameshamilton@gmail.com.
authors.forename: Trevor James
authors.initials: TJ
authors.lastname: Hamilton
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D010364:Pattern Recognition, Visual / Q000187:drug effects / Q000502:physiology*; D021641:Recognition, Psychology / Q000187:drug effects / Q000502:physiology*; D015027:Zebrafish / Q000502:physiology*
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine
keywords: Leopard danio; Memory; Neophobia; Nicotine; Novel object preference test; Novel object recognition test; Zebrafish