Exploring Neuronal Diversity in the Mammalian Brain

Hyrax neuron
By Serena Bianchi
October 11, 2010

Studying the evolution of the brain is central to understanding the origins of what makes us human. In Dr. Sherwood’s Laboratory for Evolutionary Neuroanatomy, we investigate brain evolution by examining and comparing the brain structure of primates and other mammalian species through a variety of techniques. As part of a project on the evolution of neuronal diversity in mammals, last summer I had the opportunity to “peek” into the neocortex of an Afrotherian species related to the African elephant, the rock hyrax. My work consisted in identifying and comparing distinct neuronal morphologies across two regions of the rock hyrax neocortex and providing a comparison with the related African elephant.

This study was interesting to me in two main respects. First, Afrotheria offer the opportunity to study aspects of brain evolution within a taxonomic group that diverged from other mammals about 100 million years ago. Second, the technique we used to stain the tissue—Golgi staining—is particularly exciting because it shows the entire structure of the neurons, from the cell body to the spider-leg-like dendrites. By staining a random sample of neurons, this technique reveals the neocortex as an intricate network of distinct, variously shaped cells. I must admit that the first time I looked at a Golgi stain under the microscope I was amazed at the mysterious beauty of those mind-begetting neural landscapes.