Is senile dementia associated with increased plasticity of synapses?

Usually, post-mortem examination of brain tissue samples of patients with age-related neurodegenerative diseases demonstrates pronounced atrophic changes at all levels of organization.

This is manifested not only by the small thickness and density of the cortex, but also by a significant expansion of the ventricles of the brain.

The same changes are detected in the tissue of the aging brain even in the absence of neurodegenerative diseases.

Traditionally, it was believed that the aging brain is also characterized by degeneration of synapses – interneuronal contacts that provide information transmission.

However, the results of a recent study conducted by scientists at Imperial College London, on the contrary, demonstrated increased plasticity of axons – synapse–forming processes of nerve cells - in the cerebral cortex of old mice.

Based on the observations made, the authors concluded that the behavioral deviations characteristic of old animals are not due to the loss of synaptic plasticity, but, on the contrary, its increase, making it impossible to maintain a stable synaptic structure of the brain.

The study of the brain tissue of old mice using two-photon microscopy revealed a significant increase in the rate of formation of new and disappearance of existing synapses compared with the indicators characteristic of the brain of young animals.

It was also found that, despite the comparable density and size of the synapses of the old and young brains, the synapses of the old brain are characterized by much more pronounced size fluctuations.

It is believed that a change in the structure of synapses underlies the formation of long-term memory, while the size of the synapse is used to assess its significance. It is quite possible that the age-related deterioration of the ability to memorize and learn new skills is due not only to increased plasticity, but also to the instability of the size of the synapses of the aging brain.

Article by Federico W. Grillo et al. Increased axonal bouton dynamics in the aging mouse cortex is published in the journal Proceedings of the National Academy of Sciences

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Medical Xpress: Structural dynamics underlying memory in aging brains.

19.04.2013