Laboratory of Electron Microscopy


The lab opened in 1966 when Dr. Alan Peters assumed the position of Waterhouse Professor and Chairman of the Department of Anatomy.  The focus of the lab was electron microscopy, the goal, to characterize the fine structure of synapses and cell types, neurons and neuroglia, in the cerebral cortex.

Over the past several years we have examined the organization of neurons in cerebral cortex, with emphasis on the pyramidal cell modules. But more recently our focus has been on the effects of aging on primary cerebral cortex and white matter.


The pyramidal cell module By combining the results of careful cell counts, with antibody studies we have defined the pyramidal cell module, which we propose to be the smallest functional unit of cortex.(Figure A)

The cells in figure B and C are stained with an antibody to Calbindin. Photographed with Nomarsky optics, (figure B) bundles of axons are clearly visible as they cascade below the cell bodies. When visualized with a fluorescent marker and viewed in cross section on the confocal microscope (figure C) each bundle of axons appear as a brightly staining cluster.

With the addition of immunocytochemistry and confocal microscopy we have been able to modify the original diagram to include some of the inhibitory neurons in the modules (figure D).

We are now focusing on the effects of normal aging on the cerebral cortex and white matter. To carry out these studies we use electron microscopy, confocal microscopy, antibodies, and stereology, to try to determine which of the morphological changes that occur with age are responsible for the cognitive decline exhibited by aging primates.


This pair of electron micrographs illustrates some of the changes that occur in visual cortex with age. On the far left is an example of young, normal, myelinated axons. In an aging cortex, the myelin sheaths exhibit changes such as splits, ballooning, and dark cytoplasmic inclusions.


Since the focus of the laboratory is electron microscopy, most techniques used in the lab, or developed here are designed specifically for the electron microscope


Apart from the personnel listed below, currently Dr. Peters lab has no full time grad students or post-docs. The lab does host grad students from other labs who are interested in learning and applying electron microscopic techniques to support their theses.

Alan Peters, Ph.D
Since retiring from the position of Chairman of the Department in 1998, Alan Peters is now doing full time research into the effects of normal aging on cerebral cortex. Related website: Fine Structure of the Aging Brain

Claire Sethares, Neuroscience Technologist
With the lab since 1986, Claire provides technical assistance and manages the lab.


The most recent publications from our laboratory have been concerned with the effects of normal aging on cerebral cortex and white matter tracts of the monkey brain.

Peters, A and Sethares, C. 2012. Age-related changes in the morphology of cerebral capillaries do not correlate with cognitive decline. J. Comp. Neurol. 520: 1339 – 1347.

Ludvigson, A.E., Luebke, J.I., Lewis, J., and Peters, A. 2011 Structural abnormalities in the cortex of the rTg4510 mouse model of tauopathy: a light and electron microscope study. Brain Struct. Funct. 216: 31 – 42.

Peters, A and Kemper, T. 2011.  A review of the structural alterations in the cerebral hemispheres of the aging rhesus monkey/ Neurobiol. Aging.

Bowley, M.P., Cabral, H., Rosene, D.L. and Peters, A. 2010 Age changes in myelinated nerve fibers of the cingulate bundle and corpus callosum in the rhesus monkey. J. Comp. Neurol. 518: 3046 – 3064.

Kirschner, D.A., Avila, R.L., Gamez Sazo, R.E., Luoma, A., Ezmann, G.U., Agrawal, D., Inouye, H., Bunge, M.B., Kocsis, J., Peters, A., and Whitmore, S.R. 2010 Rapid assessment of internodal myelin integrity in central nervous system. J. Neurosci. Res. 88: 712 – 723.

Luebke, J., Barbas, H. and Peters, A. 2010 Effects of normal aging on prefrontal area 46 in the rhesus monkey. Brain Res Rev. 62: 212 – 232.

Peters, A. 2010 The morphology of minicolumns. In: The Neurochemical Basis of Autism: From Molecules to Minicolumns. ed. G.J. Blatt Springer, New York pp. 69 – 82.

Peters, A., Sethares, C., and Moss, M.B. 2010 How the primate fornix is affected by age. J. Comp. Neurol. 518: 3962 – 3980.

Soghomonian J.J., Sethares C., and Peters, A. 2010 Effects of age on axon terminals forming axosomatic and axodendritic inhibitory synapses in prefrontal cortex. Neuroscience 168: 74 – 81.

Peters, A. 2009 The effects of normal aging on myelinated nerve fibers in monkey central nervous system.  Frontiers in Neuroanatomy 3: 1 –10