Identification of segmental neural circuits controlling trunk motor coordination
The control of trunk muscles is essential for all movements, from standing and walking in quadrupedal and bipedal animals, to enabling a stunning dance routine or a successful sport performance in humans. Trunk muscle control in animals without limbs, such as fish and snakes, or in limbed animals share many fundamental features. Limbless animals are able to move via a longitudinal coordinated wave of muscle contractions combined with segmental alternating contractions which respond to sensory input to produce corrections and thus keeping a fluid movement. With the evolution of limbs, trunk neural networks had to now interact with these new limb-related networks and with sensory feedback to produce movement. The control of movement in vertebrates has been mostly focused on limb-related neural networks while trunk-related neural circuits have been largely unexplored. Thus, fundamental questions remain unanswered: Have the trunk neural networks of mammals preserved basic circuit elements of their limbless vertebrate ancestors? How is the trunk-related neural circuitry of limbed mammals organized? How does this network coordinate motor activity with or without limb-related networks? And, what is the role of sensory input in the modulation and/or control of thoracic motor output? Preliminary results show that the isolated thoracic spinal cord can produce synchronous or alternating patterns of motor activity which are mediated by polysynaptic or monosynaptic synaptic pathways, respectively, allowing this neural network to function autonomously or in coordination with limb-related circuits. This supports our overarching hypothesis that the thoracic neural circuitry is a central pattern generator (CPG) network (defined as neural circuits that generate periodic motor commands which control movement). Thus, we propose to identify the organization of the trunk neural network using: (1) an in-vitro thoracic cord preparation coupled with extracellular recordings to identify trunk neural network components operating with or without limb-related circuits; (2) calcium imaging in wild type and transgenic mice to identify and characterize key neuronal populations responsible for the generation of trunk rhythmic activity; (3) a novel spinal cord-muscle attached preparation to characterize the effects of sensory stimulation on trunk motor output.
The control of trunk muscles is essential for all movements, from standing and walking in quadrupedal and bipedal animals, to enabling a stunning dance routine or a successful sport performance in humans. Trunk muscle control in animals without limbs, such as fish and snakes, or in limbed animals share many fundamental features. Limbless animals are able to move via a longitudinal coordinated wave of muscle contractions combined with segmental alternating contractions which respond to sensory input to produce corrections and thus keeping a fluid movement. With the evolution of limbs, trunk neural networks had to now interact with these new limb-related networks and with sensory feedback to produce movement. The control of movement in vertebrates has been mostly focused on limb-related neural networks while trunk-related neural circuits have been largely unexplored. Thus, fundamental questions remain unanswered: Have the trunk neural networks of mammals preserved basic circuit elements of their limbless vertebrate ancestors? How is the trunk-related neural circuitry of limbed mammals organized? How does this network coordinate motor activity with or without limb-related networks? And, what is the role of sensory input in the modulation and/or control of thoracic motor output? Preliminary results show that the isolated thoracic spinal cord can produce synchronous or alternating patterns of motor activity which are mediated by polysynaptic or monosynaptic synaptic pathways, respectively, allowing this neural network to function autonomously or in coordination with limb-related circuits. This supports our overarching hypothesis that the thoracic neural circuitry is a central pattern generator (CPG) network (defined as neural circuits that generate periodic motor commands which control movement). Thus, we propose to identify the organization of the trunk neural network using: (1) an in-vitro thoracic cord preparation coupled with extracellular recordings to identify trunk neural network components operating with or without limb-related circuits; (2) calcium imaging in wild type and transgenic mice to identify and characterize key neuronal populations responsible for the generation of trunk rhythmic activity; (3) a novel spinal cord-muscle attached preparation to characterize the effects of sensory stimulation on trunk motor output.
