Abstract
Aging is accompanied by a progressive decrease in learning and memory function. Synaptic loss, one of the hallmarks of normal aging, likely plays an important role in age-related cognitive decline. But little is known about the impact of advanced age on synaptic plasticity and neuronal function in vivo. In this study, we examined the structural dynamics of postsynaptic dendritic spines as well as calcium activity of layer 5 pyramidal neurons in the cerebral cortex of young and old mice. Using transcranial two-photon microscopy, we found that in both sensory and motor cortices, the elimination rates of dendritic spines were comparable between young (3–5 months) and mature adults (8–10 months), but seemed higher in old mice (>20 months), contributing to a reduction of total spine number in the old brain. During the process of motor learning, old mice compared to young mice had fewer new spines formed in the primary motor cortex. Motor training-evoked somatic calcium activity in layer 5 pyramidal neurons of the motor cortex was also lower in old than young mice, which was associated with the decline of motor learning ability during aging. Together, these results demonstrate the effects of aging on learning-dependent synapse remodeling and neuronal activity in the living cortex and suggest that synaptic deficits may contribute to age-related learning impairment.
Highlights
The normal aging process is accompanied by a progressive decrease in cognitive and learning ability (Hedden and Gabrieli, 2004; Brayne, 2007; Deary et al, 2009)
Using the in vivo imaging approach, we examined dendritic spine formation and elimination in response to motor skill learning in young adult and old mice
We found that spine elimination was higher in old than young adult mice under basal conditions, while motor learning-induced spine formation was reduced in old mice
Summary
The normal aging process is accompanied by a progressive decrease in cognitive and learning ability (Hedden and Gabrieli, 2004; Brayne, 2007; Deary et al, 2009). Neuropsychological tests have revealed that people older than 60 years of age often show impairments in certain types of memory, especially recall of recent events (Shimamura, 1994; Zelinski and Burnight, 1997). Aging-related cognitive decline leads to decreased quality of life and lowered ability to function. As the average lifespan is increasing worldwide, it becomes increasingly important to understand the neural mechanisms of age-related cognitive impairment. The cellular basis of age-related cognitive decline remains unclear. It was once believed that a generalized neuronal loss in the cerebral cortex and deterioration of dendritic branching occurs during normal aging and contributes to cognitive impairment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
