Key periods of cognitive decline in a nonhuman primate model of cognitive aging, the common marmoset (Callithrix jacchus).

It is well established that human life expectancy increases considerably with an ever-growing number of people suffering from age-related cognitive decline and degenerative brain diseases. This necessitates the development of animal models to counteract or stop the progression of the decline early enough. Presently, primate models are few, and many studies argue for the marmoset as an interesting primate model presenting a short life span and being easily available in research laboratories. In this article, we propose the marmoset as a valid model for cognitive decline. Using a computer touch screen, we trained 35 marmosets from 2 to 14 years of age to perform reversal learning and delayed-matching-to-position tasks. We found typical age-related cognitive deficits related to executive functions and spatial working memory. Applying a recursive algorithm, we detected 2 critical periods from which deficits appear. Mainly, response strategy deficits appear from age 4, whereas impairments in inhibitory control appear from age 7-8. Furthermore, the presence of outliers, sometimes at an early age, suggests pathological cognitive deficits that would require imaging exploration in parallel to behavior.