There are many characteristics that distinguish one type of neuron from another, such as where it is located or what it looks like. We needed to classify the varieties of V1 interneurons in a much more systematic and detailed manner-information that would then help to decipher the circuits that underlie movement at an unprecedented organizational level.' 'Previous studies had shown that V1 interneurons are intimately involved in shaping motor neuron activity, but had been unable to determine precisely how they did so. 'Motor neurons are like the strings of a marionette, with interneurons directing which strings are to be pulled, and in what order,' said Jay Bikoff, PhD, a postdoctoral scholar at Columbia and first author of one of the papers. In today's newly published research, scientists focused on a group of neurons in the spinal cord called V1 interneurons, which form connections that orchestrate the activity and output of motor neurons, the class of neurons that give us the power to move. And once we understand the brain at this level, there are key problems of circuitry and function that can be addressed at a detailed level of resolution.' 'As we continue to build upon and refine this method, scientists could take any cellular circuit and reveal its basic component parts. Jessell, PhD, senior author on one of the papers and a co-director of the Zuckerman Institute. 'Our work allows scientists to assess the diversity of neuronal cell classes in specific regions of the central nervous system-in part by plugging basic cellular characteristics into this fundamental statistical model,' said Thomas M.

The papers are published online in the journal Cell.

How many neurons in human brain