Dissecting the specificity of hindbrain premotor circuits

MARIA SOLEDAD ESPOSITO; PAOLO CAPELLI; SILVIA ARBER

Barcelona

Congreso; 8th Fens Forum of Neuroscience; 2012

Movement is the ultimate output of brain processing. Motor signals are transmitted from the brain to the spinal cord through many descending pathways such as: corticospinal, rubrospinal, vestibulospinal and reticulospinal. In higher animals, direct input from the cortex to motor neurons is thought to control precise voluntary movements. However in evolutionarily lower animals, such as mice, the major cortical impact on motor neurons is most likely mediated by disynaptic circuits through relay stations located in the spinal cord and/or brainstem. In this project we study the distribution and function of premotor input to motor neurons from the hindbrain. We show that many cells in this region are monosynaptically connected to motor neurons, highlighting a potential direct circuit for the control of precise motor behavior. We found that different motor neuron pools are differentially regulated by hindbrain premotor circuits. The caudal most part of the reticular formation contains premotor cells that synapse with specific sets of motor neurons innervating forelimb muscles. Premotor MdV neurons are glutamatergic, receive direct cortical input and are involved in the performance of skilled motor tasks. We postulate that MdV could be part of a modular system that controls the co-activation of motor neurons (synergies) during specific tasks. We hypothesize that MdV neurons could mediate cortical signals during reaching movements.