Learning-Dependent Dendritic Spine Plasticity Is Reduced in the Aged Mouse Cortex

Area of Science:

• Neuroscience
• Aging Research
• Cognitive Decline

Background:

• Aging leads to reduced learning and memory.
• Synaptic loss is a key feature of aging and cognitive decline.
• The impact of advanced age on synaptic plasticity and neuronal function in vivo is not well understood.

Purpose of the Study:

• To investigate the effects of aging on synaptic plasticity and neuronal function in the cerebral cortex.
• To examine structural dynamics of postsynaptic dendritic spines and calcium activity in young and old mice.

Main Methods:

• Utilized transcranial two-photon microscopy.
• Examined layer 5 pyramidal neurons in the sensory and motor cortices of young and old mice.
• Assessed dendritic spine elimination and formation rates, and measured motor training-evoked somatic calcium activity.

Main Results:

• Dendritic spine elimination rates were higher in old mice (>20 months) compared to young (3-5 months) and mature adult (8-10 months) mice.
• Old mice exhibited reduced formation of new dendritic spines in the motor cortex during motor learning.
• Motor learning-induced calcium activity in motor cortex neurons was lower in old mice, correlating with impaired motor learning ability.

Conclusions:

• Aging significantly affects learning-dependent synapse remodeling and neuronal activity in the living cortex.
• Synaptic deficits, including reduced spine number and altered neuronal activity, likely contribute to age-related learning and memory impairments.