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Cereb Cortex. 2015 Jun;25(6):1454-68. doi: 10.1093/cercor/bht336. Epub 2013 Dec 8.

Age-related changes to layer 3 pyramidal cells in the rhesus monkey visual cortex.

Author information

1
Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and.
2
Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
3
Fishberg Department of Neuroscience and Friedman Brain Institute.
4
Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and Department of Mathematics, Franklin and Marshall College, Lancaster, PA 17604, USA.
5
Fishberg Department of Neuroscience and Friedman Brain Institute Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and.

Abstract

The effects of normal aging on morphologic and electrophysiologic properties of layer 3 pyramidal neurons in rhesus monkey primary visual cortex (V1) were assessed with whole-cell, patch-clamp recordings in in vitro slices. In another cohort of monkeys, the ultrastructure of synapses in the layers 2-3 neuropil of V1 was assessed using electron microscopy. Distal apical dendritic branching complexity was reduced in aged neurons, as was the total spine density, due to specific loss of mushroom spines from the apical tree and of thin spines from the basal tree. There was also an age-related decrease in the numerical density of symmetric and asymmetric synapses. In contrast to these structural changes, intrinsic membrane, action potential (AP), and excitatory and inhibitory synaptic current properties were the same in aged and young neurons. Computational modeling using morphologic reconstructions predicts that reduced dendritic complexity leads to lower attenuation of voltage outward from the soma (e.g., backpropagating APs) in aged neurons. Importantly, none of the variables that changed with age differed in neurons from cognitively impaired versus unimpaired aged monkeys. In summary, there are age-related alterations to the structural properties of V1 neurons, but these are not associated with significant electrophysiologic changes or with cognitive decline.

KEYWORDS:

computational modeling; dendritic spines; electron microscopy; slice electrophysiology; synapses

PMID:
24323499
PMCID:
PMC4428297
DOI:
10.1093/cercor/bht336
[Indexed for MEDLINE]
Free PMC Article

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