title: Cortical cell and neuron density estimates in one chimpanzee hemisphere.
abstract: The density of cells and neurons in the neocortex of many mammals varies across cortical areas and regions. This variability is, perhaps, most pronounced in primates. Nonuniformity in the composition of cortex suggests regions of the cortex have different specializations. Specifically, regions with densely packed neurons contain smaller neurons that are activated by relatively few inputs, thereby preserving information, whereas regions that are less densely packed have larger neurons that have more integrative functions. Here we present the numbers of cells and neurons for 742 discrete locations across the neocortex in a chimpanzee. Using isotropic fractionation and flow fractionation methods for cell and neuron counts, we estimate that neocortex of one hemisphere contains 9.5 billion cells and 3.7 billion neurons. Primary visual cortex occupies 35 cm(2) of surface, 10% of the total, and contains 737 million densely packed neurons, 20% of the total neurons contained within the hemisphere. Other areas of high neuron packing include secondary visual areas, somatosensory cortex, and prefrontal granular cortex. Areas of low levels of neuron packing density include motor and premotor cortex. These values reflect those obtained from more limited samples of cortex in humans and other primates.
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN 37240; Eli Lilly and Company, Indianapolis, IN 46285;
authors.forename: Christine E
authors.initials: CE
authors.lastname: Collins
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN 37240;
authors.forename: Emily C
authors.initials: EC
authors.lastname: Turner
authors.affiliation: Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37240;
authors.forename: Eva Kille
authors.initials: EK
authors.lastname: Sawyer
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN 37240;
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Reed
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN 37240; Department of Neuroscience, Neuroscience Research Institute, The Ohio State University College of Medicine, Columbus, OH 43210;
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Young
authors.affiliation: Vanderbilt University Medical Center, Flow Cytometry Shared Resource, Nashville, TN 37232.
authors.forename: David K
authors.initials: DK
authors.lastname: Flaherty
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN 37240; jon.h.kaas@vanderbilt.edu.
authors.forename: Jon H
authors.initials: JH
authors.lastname: Kaas
mesh_terms: D000375:Aging; D000818:Animals; D002452:Cell Count; D005260:Female; D009044:Motor Cortex / Q000166:cytology; D019579:Neocortex / Q000166:cytology*; D009474:Neurons / Q000166:cytology*; D002679:Pan troglodytes / Q000502:physiology*; D013003:Somatosensory Cortex / Q000166:cytology; D014793:Visual Cortex / Q000166:cytology
keywords: flow fractionator; isotropic fractionator; neuron density; primate neocortex; visual cortex