Mammalian behaviour is characteristically complex, yet ultimately manifests as specific motor instructions within output circuitries of the spinal cord. Locomotion is a behavior that is universal to the animal kingdom. Initiation of locomotion is governed by descending command neurons, which instruct spinal networks to adopt a specific locomotor gait and determine locomotor speed. Given that the commands for gait and speed are symmetric, it has remained to be found what descending circuits enable mammals to move left or right—circuits which would be required for any goal-directed movement. In the first part of the seminar, I will present our discovery that a small group of transcriptionally defined neurons act as the descending system that controls the left/right direction of locomotor movements in mammals. To elaborate this discovery, we used a sophisticated suite of anatomical, electrophysiological, and behavioral approaches that demonstrate Chx10 spinal projection neurons are required for moving left or right. Uniquely, these so-called reticulospinal neurons interface between brain networks that orchestrate behavior and those spinal networks that execute discrete motor actions. In the second part of my talk, I will present some of my more recent work focused on unravelling the contribution of distinct upstream nuclei in controlling movement asymmetries. The discovery of brain circuits that enable motor asymmetries has extraordinary implication; the decision to move left or right is one of the most fundamental behavioral choices the brain makes.

Jared Cregg is a postdoctoral fellow in Ole Kiehn’s lab at the University of Copenhagen (Denmark). Jared received his PhD in Neurosciences from Case Western Reserve University (USA) in 2018. His graduate work under the mentorship of Dr. Jerry Silver focused on understanding how phrenic motor neurons—those neurons which innervate the diaphragm—are controlled by premotor networks. Jared’s current research is aimed at understanding how motor actions are organized at the behavioural level.



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