Across species, bigger brains usually mean better cognition. But, this relationship rarely holds when considering individual differences within a species. Within species, the number of neurons in the brain may be a better proxy for cognitive ability than brain size. Further, the number of neurons may be independent of brain size. But how to measure neuron number?
Levi Storks, a graduate student in Manuel Leal’s lab at the University of Missouri, set out to do just that. He adapted a protocol that has previously been used in mammals, birds, and crocodiles, but never before in lizards. In brief, he dissected the telencephalon, cerebellum, and other regions of the brain of an Anolis cristatellus and used the isotropic fractionator method to determine neuron number in each of the three. After homogenizing each tissue, he used a double-labeling technique with DAPI to stain each nucleus and neuronal nuclei antibody to stain each neuron, and used a hemocytometer to count the cells under magnification. Now that this protocol is working, look out for Levi’s future results on anole brain structure and cognition!