QnAs with Thomas Jessell.

Abstract

Over long years, neuroscientists have attempted to trace in cartographic detail the neural circuitry underlying goal-oriented movements, such as reaching, grasping, and handling objects. The modularity, precision, and smoothness of such movements arise from motor commands that descend from the brain to muscles, triggering rapid and continual feedback, which in turn helps fine tune the impact of descending commands. Such interlacing flow of electrical signals through sprawling neuronal networks underlies the fine motor skills that mammals summon with seeming ease in the service of routine tasks. But the identity of the neurons that seem to effortlessly thread their way through limb muscles, the spinal cord, and the brain to furnish such rapid feedback has long remained veiled from the mapmakers’ view. Using molecular sleight of hand to manipulate individual groups of neurons in the spinal cord of mice, Columbia University neuroscientist Thomas Jessell and his team uncovered neuronal control systems that help rodents reach for objects with characteristic precision and smoothness. At the 14th Annual Sackler Lecture, titled “Deconstructing circuits for motor behavior,” presented to the National Academy of Sciences in Washington, DC in March 2014 as part of the Arthur M. Sackler Colloquium, “Epigenetic Changes in the Developing Brain: Effects on Behavior,” Jessell described his findings, which might help decode the logic of neuronal rewiring in people with crippling ailments such as spinal cord injury. PNAS spoke to Jessell about the significance of his discoveries. Tom Jessell. Image courtesy of Jill LeVine (Jill LeVine Photography, New York). > PNAS:Forelimb movements such as goal-directed reaching are considered sophisticated motor skills. Are such forms of movement uniquely mammalian? > Jessell:Primitive vertebrates had fins instead of limbs with digits, and movement largely involved contraction of undulating muscles for buoyancy and swimming. The ability to perform dexterous movements, such as those involved in …