Abstract
The mouse lemur (Microcebus murinus) is a promising primate model for investigating normal and pathological cerebral aging. The locomotor behavior of this arboreal primate is characterized by jumps to and from trunks and branches. Many reports indicate insufficient adaptation of the mouse lemur to experimental devices used to evaluate its cognition, which is an impediment to the efficient use of this animal in research. In order to develop cognitive testing methods appropriate to the behavioral and biological traits of this species, we adapted the Lashley jumping stand apparatus, initially designed for rats, to the mouse lemur. We used this jumping stand apparatus to compare performances of young (n = 12) and aged (n = 8) adults in acquisition and long-term retention of visual discriminations. All mouse lemurs completed the tasks and only 25 trials, on average, were needed to master the first discrimination problem with no age-related differences. A month later, all mouse lemurs made progress for acquiring the second discrimination problem but only the young group reached immediately the criterion in the retention test of the first discrimination problem. This study shows that the jumping stand apparatus allows rapid and efficient evaluation of cognition in mouse lemurs and demonstrates that about half of the old mouse lemurs display a specific deficit in long-term retention but not in acquisition of visual discrimination.
Highlights
As age-related cognitive impairment has become a major health problem in our societies, the need for valid animal model to investigate the biological basis of this decline and to develop efficient treatments is a crucial concern
Our findings demonstrate that naive mouse lemurs are able to master a visual discrimination task in a very small number of trials (13 to 41) after a short habituation session of only seven trials
The cognitive demand being identical in all these discrimination tasks, the excellent performance of mouse lemurs in the jumping stand apparatus was likely based on sensory, motor, attentional and motivational parameters that make this procedure appropriate to their biology
Summary
As age-related cognitive impairment has become a major health problem in our societies, the need for valid animal model to investigate the biological basis of this decline and to develop efficient treatments is a crucial concern. Jumping Stand Apparatus for Mouse Lemur Primates length 12 cm, 60–120 g) rendering its breeding and housing cost-efficient, this nocturnal, rapidly maturing (puberty occurs at about 6–8 months) and short-lived (about a decade in captivity) primate offers a useful compromise between the practicalities and affordability of rodents and the evolutionary proximity to humans of monkeys or apes This proximity was well illustrated by many studies that have brought out similarities of mouse lemurs and humans in the age-related changes occurring in brains, including amyloid plaque formation and neurofibrillary changes [2,3]; pathological tau metabolism [4]; neurochemical alterations [5]; neuronal loss in specific cerebral structures (e.g., the nucleus basalis of Meynert) [6]; iron accumulation [7]; and varying patterns of cerebral atrophy [8]. The atrophy of some brain regions such as septum, hippocampus or entorhinal cortex was only detected in a subcategory of aged mouse lemurs and was correlated with cognitive impairments, which suggests that it is related to pathological aging [9]
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