title: Fractal analysis reveals subclasses of neurons and suggests an explanation of their spontaneous activity.
abstract: The present work used fractal time series analysis (detrended fluctuation analysis; DFA) to examine the spontaneous activity of single neurons in an anesthetized animal model, specifically, the mitral cells in the rat main olfactory bulb. DFA bolstered previous research in suggesting two subclasses of mitral cells. Although there was no difference in the fractal scaling of the interspike interval series at the shorter timescales, there was a significant difference at longer timescales. Neurons in Group B exhibited fractal, power-law scaled interspike intervals, whereas neurons in Group A exhibited random variation. These results raise questions about the role of these different cells within the olfactory bulb and potential explanations of their dynamics. Specifically, self-organized criticality has been proposed as an explanation of fractal scaling in many natural systems, including neural systems. However, this theory is based on certain assumptions that do not clearly hold in the case of spontaneous neural activity, which likely reflects intrinsic cell dynamics rather than activity driven by external stimulation. Moreover, it is unclear how self-organized criticality might account for the random dynamics observed in Group A, and how these random dynamics might serve some functional role when embedded in the typical activity of the olfactory bulb. These theoretical considerations provide direction for additional experimental work.
authors.affiliation: Department of Philosophy, University of Central Florida, Orlando, FL, United States; Cognitive Sciences Program, University of Central Florida, Orlando, FL, United States. Electronic address: luis.favela@ucf.edu.
authors.forename: Luis H
authors.initials: LH
authors.lastname: Favela
authors.affiliation: Department of Psychology, College of the Holy Cross, Worcester, MA, United States. Electronic address: coeyca@mail.uc.edu.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Coey
authors.affiliation: Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States. Electronic address: edwin.griff@uc.edu.
authors.forename: Edwin R
authors.initials: ER
authors.lastname: Griff
authors.affiliation: Center for Cognition, Action, and Perception, Department of Psychology, University of Cincinnati, Cincinnati, OH, United States. Electronic address: michael.richardson@uc.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Richardson
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D017709:Fractals; D009474:Neurons / Q000145:classification* / Q000502:physiology*; D009830:Olfactory Bulb / Q000502:physiology*; D051381:Rats; D012815:Signal Processing, Computer-Assisted
keywords: Detrended fluctuation analysis; Fractal scaling; Mitral cells; Olfactory bulb; Self-organized criticality; Spontaneous activity