Recognition memory in tree shrew (Tupaia belangeri) after repeated familiarization sessions

Abstract

Recognition memories are formed during perceptual experience and allow subsequent recognition of previously encountered objects as well as their distinction from novel objects. As a consequence, novel objects are generally explored longer than familiar objects by many species. This novelty preference has been documented in rodents using the novel object recognition (NOR) test, as well is in primates including humans using preferential looking time paradigms. Here, we examine novelty preference using the NOR task in tree shrew, a small animal species that is considered to be an intermediary between rodents and primates. Our paradigm consisted of three phases: arena familiarization, object familiarization sessions with two identical objects in the arena and finally a test session following a 24-h retention period with a familiar and a novel object in the arena. We employed two different object familiarization durations: one and three sessions on consecutive days. After three object familiarization sessions, tree shrews exhibited robust preference for novel objects on the test day. This was accompanied by significant reduction in familiar object exploration time, occurring largely between the first and second day of object familiarization. By contrast, tree shrews did not show a significant preference for the novel object after a one-session object familiarization. Nonetheless, they spent significantly less time exploring the familiar object on the test day compared to the object familiarization day, indicating that they did maintain a memory trace for the familiar object. Our study revealed different time courses for familiar object habituation and emergence of novelty preference, suggesting that novelty preference is dependent on well-consolidated memory of the competing familiar object. Taken together, our results demonstrate robust novelty preference of tree shrews, in general similarity to previous findings in rodents and primates.

Varied behavioral responses induced by morphine in the tree shrew: a possible model for human opiate addiction

“…And, we thought these two indexes might be used to measure the changes of locomotor activity in tree shrews. Just like the previous study used the tracing of tree shrews’ movements to examine novelty preference for the novel object (Khani and Rainer, 2012), we also found the moving distance was significantly increased after morphine injection (Figure 6). However, this measure might not fully reflect the changes of tree shrews’ activity in the vertical direction.…”

Enhanced visual exploration for real objects compared to pictures during free viewing in the macaque monkey

“…We found little evidence of across-day habituation, indicating that monkeys' overall exploratory motivation for the same stimulus set remains constant over five daily sessions. This is somewhat surprising, given that across-day habituation of exploration of similar object stimuli has been demonstrated on other species including rodents (Reger et al, 2009) and tree shrews (Khani and Rainer, 2012). We suggest that exploration in the form of locomotion may be more sensitive to repetition than gaze exploration, since it involves energy expenditure and exposure to environmental risks; factors that are not associated with eye movements.…”

创制动物模型,为何不用树鼩呢?

“…For decades, there have been many efforts to promote the tree shrew as an experimental animal and for it to replace primates in the study of fundamental biological functions and human diseases (Amako et al, 2010; Cao et al, 2003; Fang et al, 2016; Fitzpatrick, 1996; Fuchs, 2005; Khani & Rainer, 2012; Lee et al, 2016; MacEvoy et al, 2009; Nair et al, 2014; Peng et al, 1991; Pryce & Fuchs, 2017; Su et al, 1987; Veit et al, 2011, 2014; Xu et al, 2013b; Yan et al, 1996; Zhao et al, 2002; Zheng et al, 2014). Indeed, tree shrews have many characteristics that make it a good laboratory animal, such as small body size, low-cost of maintenance, short reproductive cycle and life span, and most importantly, its close relationship to primates (Fan et al, 2013; Zheng et al, 2014).…”