New paper on synaptic reorganisation during ageing

We have a new paper in PNAS on synaptic reorganization during ageing.  It is featured in Nature and in F1000Prime.

Increased axonal bouton dynamics in the aging mouse cortex.
Grillo, F. W., Song, S., Teles-Grilo Ruivo, L. M., Huang, L., Ge, G., Knott, G. W., Maco, B., Ferretti, V., Thompson, D., Little, G. E., De Paola, V.
Proceedings of the National Academy of Sciences of the United States of America 110, E1514-E1523 (2013).
Nature Research Highlights | F1000Prime |

Learning deficits with age are thought to arise from a progressive loss of synapses and synaptic plasticity, but in vivo evidence has been lacking.  In this study we combined in vivo 2-photon microscopy with behavioural assessment and a novel, computer-based, method, called EPBscore, to rigorously track the size (i.e., strength) and location of large populations of synaptic boutons over extended periods of time, and found that:

  • Axonal arbors and their boutons continue to remodel in the aged brain.
  • The aged cortex shows circuit-specific increased rates of axonal bouton addition, elimination and destabilization.
  • Size fluctuations of persistent boutons, believed to encode long-term memories, are larger in the aged brain, while bouton size and density are not affected.
  • Increased synaptic destabilization suggests that learning deficits in the aged brain arise because of a higher probability of forgetting rather than a failure to learn.

Figure – Unstable connections.  3D reconstruction of large boutons (light blue) making connections (red) with surrounding cells (grey) in the aged brain.