title: Turtle Dorsal Cortex Pyramidal Neurons Comprise Two Distinct Cell Types with Indistinguishable Visual Responses.
abstract: A detailed inventory of the constituent pieces in cerebral cortex is considered essential to understand the principles underlying cortical signal processing. Specifically, the search for pyramidal neuron subtypes is partly motivated by the hypothesis that a subtype-specific division of labor could create a rich substrate for computation. On the other hand, the extreme integration of individual neurons into the collective cortical circuit promotes the hypothesis that cellular individuality represents a smaller computational role within the context of the larger network. These competing hypotheses raise the important question to what extent the computational function of a neuron is determined by its individual type or by its circuit connections. We created electrophysiological profiles from pyramidal neurons within the sole cellular layer of turtle visual cortex by measuring responses to current injection using whole-cell recordings. A blind clustering algorithm applied to these data revealed the presence of two principle types of pyramidal neurons. Brief diffuse light flashes triggered membrane potential fluctuations in those same cortical neurons. The apparently network driven variability of the visual responses concealed the existence of subtypes. In conclusion, our results support the notion that the importance of diverse intrinsic physiological properties is minimized when neurons are embedded in a synaptic recurrent network.
authors.affiliation: Department of Physics, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Crockett
authors.affiliation: Department of Physics, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Wright
authors.affiliation: Department of Physics, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Stephen
authors.initials: S
authors.lastname: Thornquist
authors.affiliation: Department of Pharmacology and Physiology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Ariel
authors.affiliation: Department of Physics, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Ralf
authors.initials: R
authors.lastname: Wessel
mesh_terms: D000200:Action Potentials; D000818:Animals; D008954:Models, Biological; D017966:Pyramidal Cells / Q000166:cytology*; D014426:Turtles; D014793:Visual Cortex / Q000166:cytology* / Q000502:physiology