Action Systems - neural circuits for motor control Andy Murray SWC - - PowerPoint PPT Presentation

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action systems neural circuits for motor control
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Action Systems - neural circuits for motor control Andy Murray SWC - - PowerPoint PPT Presentation

Jun 19, 2023 436 likes •973 views

Action Systems - neural circuits for motor control Andy Murray SWC Room 284 (L2 West) Lecture overview Mon 12 th Motor systems overview Andy Murray Tues 13 th Pattern generation Peter Latham Fri 16 th Computational control Maneesh Sahani

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Action Systems - neural circuits for motor control

Andy Murray SWC Room 284 (L2 West)

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Lecture overview

Motor systems overview Mon 12th Andy Murray Pattern generation Tues 13th Peter Latham Computational control Fri 16th Maneesh Sahani Cerebellum Mon 9th Tom Otis Basal Ganglia Tues 20th Marcus Stephenson-Jones Neocortex/Discussion Fri Nov 23rd Andy Murray/Maneesh Sahani

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Practical overview

Week 1

  • Build a fiber photometry rig (lecture/tutorial this afternoon)
  • Surgery – virus injection and fiber optic implant tutorial (tomorrow)

Week 2

  • Design experiments to test motor control in mice
  • Use you photometry rig to record from the mice injected in week 1
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Motor control is our only means to interact with the environment

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We are surprisingly bad at recreating natural movement

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Which parts of the nervous system are involved in motor control?

Reading: Connecting neuronal circuits for movement Arber & Costa, Science 2018

  • Vol. 360, Issue 6396, pp. 1403-1404
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Muscles and motor neurons

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Muscles and motor neurons

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Spinal circuitry – organisation of motor neurons

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Spinal circuitry – organisation of limb motor neurons

Motor unit Motor pool Motor columels Motor columns agonist antagonist

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Simple motor control is based on rhythmic movements

Extensor Flexor Hindlimb EMG

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The locomotor step cycle

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The spinal cord can generate rhythmic locomotion

Intact Spinalised (T13; 38 days)

Rossignol and Bouyer, 2004

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Build a rhythmic spinal circuit…..

Extensor Flexor

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Pacemaker neurons

Crustacean stomatogastric ganglion Respiratory centres

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Sensory pathways could drive rhythmic firing in the spinal cord

Extensor Flexor

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The spinal cord can generate rhythmic firing of motor neurons (in the absence of sensory feedback)

Machado et al., 2015

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Locomotion is based on rhythmic movements generated in the spinal cord

  • T. Graham Brown

Brown, 1914

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Reciprocal inhibition

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The unit burst generator as an alternative to the half-centre model

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The unit burst generator as an alternative to the half-centre model

Grillner

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The unit burst generator as an alternative to the half-centre model

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The diversity of spinal interneurons

Reading: Goulding, 2009. Nat. Rev. Neurosci. Circuits controlling vertebrate locomotion: moving in a new direction.

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Why do we need a brain?

1. To start/stop locomotion 2. To adjust ongoing motor commands 3. When we want conscious control over our movements

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Starting locomotion– the MLR

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Locomotor transitions and choosing a gait

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Activation of spinal CPGs – the mesencephalic locomotor region

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The MLR is conserved across species

Sirota et al., 2000

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Tomorrow’s practical – stimulating and recording from the MLR in mice

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Adapting the spinal rhythm via descending brainstem pathways

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Descending pathways modify and modulate spinal circuits

a snapshot of 27 descending tracts….

Reading: Ferreira-Pinto et al., 2018. Neuron. Connecting circuits for supraspinal control of locomotion.

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Reticulospinal pathways

Wilson and Yoshida, 1969

excite both extensors and flexor motor neurons

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Reticulospinal pathways – the command neurons for movement (?)

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Individual descending axons can influence multiple spinal circuits

Reticulospinal Vestibulospinal

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The nervous system (probably) doesn’t care about individual muscles

Markin et al., 2012; Ting and McKay, 2007

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Adaptable movement

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Movement must be flexible

Marey, 1873 Borelli, 1681 Da Vinci, ~1500

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Postural control is an active process that requires descending commands

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Postural control is an active process that requires descending commands

Macpherson and Fung, 1999

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Postural control is an active process that requires descending commands

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Postural control and balance – you only notice when it’s not there

Courtesy of Prof. Fay Horak, OHSU

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Postural pathways

Deliagina et al., 2014

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Vestibulospinal tracts

cervical lumbar Maintain balance and posture using rotation and acceleration of the head

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Fluorogold (lumbar SC) Nissl cervical lumbar

The lateral vestibular nucleus projects to all spinal levels

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Vestibulospinal pathways are required for reflexive balance control

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Vestibulospinal pathways generate a contextually appropriate motor program to maintain balance

Extensors Flexors

With lateral vestibulospinal pathway Without lateral vestibulospinal pathway

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Vestibulospinal neurons are not required for treadmill locomotion

Control Ablation

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Motor systems overview Mon 12th Pattern generation Tues 13th Computational control Fri 16th Cerebellum Mon 9th Basal Ganglia Tues 20th Neocortex/Discussion Fri Nov 23rd

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Muscles and motor neurons

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Reticulospinal pathways

have diffuse projections into the spinal cord

Liang et al., 2015