Recent advances in high-resolution imaging and reconstruction techniques, developed by Dr. Oberlaender at the Max Planck Florida Institute for Neuroscience enable researchers to automatically and reliably detect the 3D location and type of every nerve cell throughout the entire brain.
The cerebral cortex is regarded as the part of the mammalian brain that is responsible for sensory perception, motor control and cognition. Despite a long-held scientific belief that cortex is build up by repeatedly occurring elementary units, so called cortical columns, a new study published in the October 7, 2013 issue of the Proceedings of the National Academy of Science, and conducted by researchers at the Max Planck Florida Institute for Neuroscience (MPFI) and at the Max Planck Institute for Biological Cybernetics (MPIBC) in Tuebingen, Germany shows that the structure of such columns can largely deviate within individual animals, and even within a specific cortical area. In addition, the study found that these structural differences are by no means arbitrary, but reflect organizational and functional properties of the peripheral sensory organs. These findings promise to open new avenues of research on brain organization and sensory information processing.
“This study resolves a decade-old controversy whether the structure of the cerebral cortex is uniform across cortical areas and species,“ said MPFI/MPIBC neuroscientist Marcel Oberlaender, PhD, corresponding author of the paper. “By determining the exact numbers and distributions of nerve cells within almost 100 cortical columns, the substantial differences observed across columns within the same animal argue against the principle of cortical uniformity.”
The researchers conducted their study by examining the brains of rats, focusing on an area of the brain known as the vibrissal cortex, which processes information obtained from facial whiskers located along the animals’ snout. In vibrissal cortex, each cortical column corresponds to one whisker and it has been thought that the number of nerve cells within each column is the same, but this was not found to be the case in the rodents studied.
Being nocturnal animals, rats mainly rely on their whiskers as active sensory organs to explore and navigate their environment. For this reason, the whisker system is an ideal model for studying whether the brain circuits involved in processing information from different sensory organs are structured uniformly or not. By simply detecting and counting every nerve cell in the entire vibrissal cortex, the scientist sought to elucidate the general principles that underlie the cellular organization of the mammalian cortex.
On examination, they found that rat vibrissal cortex comprises about 500,000 nerve cells, the number and 3D distribution being remarkably preserved across animals. More importantly, the number of nerve cells per cortical column deviated between 10,000 and 30,000 within individual animals. Their findings were particularly striking as the differences in column organization were not random, but followed a clear motive, where the number of nerve cells per cortical column reflected the distance of the respective whisker from the ground.
“We’ve shown that the structure of the mammalian cortex is not determined by some uniformity rule, and that cortices are not build up of elementary columnar networks that can be extrapolated across cortical areas or even species,” said Dr. Oberlaender. “Instead, the organization of the cerebral cortex seems to be shaped by the information obtained at the peripheral sensory sheet, a finding that may pertain to other sensory systems and species, including people. Our findings open the possibilities of new avenues of research on the relationship between brain structure and function, for example by using quantitative anatomical studies combined with noninvasive imaging technologies suitable for humans, such as functional MRI (fMRI).”
Funding was provided by the Max Planck Florida Institute for Neuroscience, the Studienstiftung des deutschen Volkes, the Bernstein Center for Computational Neuroscience, funded by German Federal Ministry of Education and Research Grant BMBF/FKZ 01GQ1002, the Max Planck Institute for Biological Cybernetics, the Werner Reichardt Center for Integrative Neuroscience, and the Max Planck Institute of Neurobiology. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.
About the author
Dr. Oberlaender is leading the Computational Neuroanatomy group at the Max Planck Institute for Biological Cybernetics and is a guest scientist at the Max Planck Florida Institute for Neuroscience. His group focuses on the functional anatomy of circuits in the cerebral cortex that form the basis of simple behaviors (e.g. decision making). One of the group’s most significant efforts is a program dedicated to obtaining a three-dimensional map of the rodent brain. This work will provide insight into the functional architecture of entire cortical areas, and will lay the foundation for a mechanistic understanding of sensory perception and behavior.
About the Max Planck Florida Institute for Neuroscience
The first institute established by Germany’s prestigious Max Planck Society outside of Europe, the Max Planck Florida Institute is also the first research institute of its kind in North America. MPFI seeks to provide new insight into understanding the functional organization of the nervous system, its capacity to produce perception, thought, language, memory, emotion, and action. Neural circuits, the complex synaptic networks of the brain, hold the key to understanding who we are, why we behave the way we do, and how the debilitating effects of neurological and psychiatric disorders can be ameliorated. MPFI meets this challenge by forging links between different levels of analysis—genetic, molecular, cellular, circuit, and behavioral—and developing new technologies that make cutting edge scientific discoveries possible. For more information, visit www.maxplanckflorida.org