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Understanding the Motor System: From Ion Channels to Coordinated Behaviour

This paper explores the intrinsic function of motor systems, focusing on oscillatory patterns in propulsive movements such as leg and wing motions. Utilizing the lamprey model, it examines how forebrain control and spinal cord networks generate motor patterns. Key mechanisms include the role of GABAergic inputs from the basal ganglia, reticulospinal activation, and modulation by metabotropic receptors. The study assesses the impact of temperature on spinal cord circuits, addressing fundamental questions about stretch receptors and neural control during movement.

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Understanding the Motor System: From Ion Channels to Coordinated Behaviour

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  1. The intrinsic function of a motor system – from ion channels to networks and behavior S. Grillner, L. Cangiano, G.-Y. Hu, R. Thompson, R. Hill, P. Wallén

  2. 3 types of motion • Propulsive movements • Leg movements, wing movements, ondulatory trunk movements • Postural motor system • Maintain body orientation • Goal directed movements • Visuomotor coordination

  3. Motor System overview Part of major interest in this paper

  4. Oscillatory patterns in propulsive movements

  5. The lamprey model

  6. Forebrain control • Direct projections from olfactory bulb and optic nerve into ventral thalamus • Basal ganglia control the activity of v. th. by GABAergic inputs (Similar function as in mammals. e.g. MPTP) • Reticulospinal neurons activate the spinal cord locomotor activity

  7. Lamprey brainsteam-spinal cord preparation (in vitro) • Locomotion can be elicited by • stimulation in the brainsteam or • by administration of agonists • of excitatory amino acids. • Spinal cord networks produce the motor pattern. (Ondulations at 0.2-10 Hz) Can be maintained in vitro over several days at T=4-7°C

  8. Brainsteam-spinal cord circuitry Connectivity is critical for producing the motor pattern. Goal: isolate the circuitry in the spinal cord and see how it works on a detailed level.

  9. Importance of membrane properties sAHP regulates the duration of bursts due to Ca-concentration in the cell  Kca-Channels Ca enters also if the neuron is not spiking (NMDA, LVA-Ca) A whole series of mechanisms regulate the duration of bursts in the spinal cord pattern generator

  10. Calcium Imaging in dendrites The calcium signal correlates with the spiking of neurons in the ipsilateral ventral root.

  11. Modulatory effect of metabotropic receptors

  12. Implement the findings in amodel

  13. Questions and next steps • What is the influence of using T=4°C? • Why are there stretch receptors, when the model works fine without? • Include control mechanisms from brain: e.g. how to swim a curve. • Can all metabotropic effects be included? These are the „interesting“ mechanisms.

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