Open AccessThe effects of aging on neuropil structure in mouse somatosensory cortex—A 3D electron microscopy analysis of layer 1
Author(s) -
Corrado Calì,
Marta Wawrzyniak,
Carlos Becker,
Bohumil Maco,
Marco Cantoni,
Anne Jorstad,
Biagio Nigro,
Federico W. Grillo,
Vincenzo De Paola,
Pascal Fua,
Graham Knott
Publication year - 2018
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0198131
Subject(s) - neuropil , excitatory postsynaptic potential , somatosensory system , neuroscience , axon , dendritic spine , inhibitory postsynaptic potential , synapse , biology , cortex (anatomy) , anatomy , central nervous system , hippocampal formation
This study has used dense reconstructions from serial EM images to compare the neuropil ultrastructure and connectivity of aged and adult mice. The analysis used models of axons, dendrites, and their synaptic connections, reconstructed from volumes of neuropil imaged in layer 1 of the somatosensory cortex. This shows the changes to neuropil structure that accompany a general loss of synapses in a well-defined brain region. The loss of excitatory synapses was balanced by an increase in their size such that the total amount of synaptic surface, per unit length of axon, and per unit volume of neuropil, stayed the same. There was also a greater reduction of inhibitory synapses than excitatory, particularly those found on dendritic spines, resulting in an increase in the excitatory/inhibitory balance. The close correlations, that exist in young and adult neurons, between spine volume, bouton volume, synaptic size, and docked vesicle numbers are all preserved during aging. These comparisons display features that indicate a reduced plasticity of cortical circuits, with fewer, more transient, connections, but nevertheless an enhancement of the remaining connectivity that compensates for a generalized synapse loss.