corticospinal pathways to control balance Stphane Baudry - - PowerPoint PPT Presentation

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corticospinal pathways to control balance
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corticospinal pathways to control balance Stphane Baudry - - PowerPoint PPT Presentation

Aug 19, 2023 10 likes •350 views

Laboratory of Applied Biology ULB Neuroscience Institute Universit Libre de Bruxelles Aging changes the contribution of spinal and corticospinal pathways to control balance Stphane Baudry Gravity-driven instability of upright posture

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Aging changes the contribution of spinal and corticospinal pathways to control balance

Stéphane Baudry

Laboratory of Applied Biology ULB Neuroscience Institute Université Libre de Bruxelles

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Gravity-driven instability of upright posture

Abrahamova and Hlavacka, 2008

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Neuromuscular components of upright standing: reflex standing? Decerebrate cat

Brainstem transection

(Sherrington 1910)

CoM CoM

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Neuromuscular components of upright standing: reflex standing?

Afferent information Muscle activation Maintaining upright standing Spinal network

Decerebrate cat

Brainstem transection

(Sherrington 1910)

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Neuromuscular components of upright standing: supraspinal component?

Ultrasound image Loram et al. 2004

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Neuromuscular components of upright standing

Afferent information Muscle activation Maintaining upright standing Defining “Postural set” Sensorimotor integration Spinal network

Supraspinal structures

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Spinal and corticospinal inputs onto soleus motoneurons

Muscle spindles pathway Muscle activation Maintaining upright standing Corticospinal pathway Soleus motor neurons

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Muscle spindles pathway

Group Ia afferents (from muscle spindles) Motor axons Motoneurons Presynaptic terminals Hoffmann (H) reflex

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Muscle spindles pathway

M wave H reflex

5 ms 2 mV

Intensity

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Influence of age on H reflex during upright standing

Baudry 2016

n = 142

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Reflex gain

Klass et al. 2011

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Presynaptic origin for the greater H-reflex modulation in older?

Baudry and Duchateau 2012

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Presynaptic origin for the greater H-reflex modulation in older?

Baudry and Duchateau 2012

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Presynaptic origin for the greater H-reflex modulation in older?

Baudry and Duchateau 2012

PADs MNs Ia afferents  Ia Presynaptic inhibition

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Greater decrease in H reflex from seated to standing in older

Baudry et al. 2015

n=40

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Reduced synaptic inputs from group I afferents with age

Soleus motor neuron pool

  • Muscle spindles

afferent inputs

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Increased feedback latency

H reflex

Latency Young Middle-aged Older

 Increase in time-delayed feedback  Reduction in synchronisation of synaptic inputs

Scaglioni et al. 2003

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Decreased reflex mechanical output

Scaglioni et al. 2003

 Torque output  Rate of torque development Young Older

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Decreased relevance of muscle spindles afferents in upright standing

Muscle spindles afferent inputs Soleus motor neuron pool

  •  latency

 Mechanical

  • utput
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MEP

Corticospinal pathway

TMS Corticospinal cells Cortico-cortical cells Interneurones Motorneurones + + +- + + +-

Spinal cord Transcranial magnetic stimulation - TMS

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MEP

Corticospinal pathway

Transcranial magnetic stimulation - TMS

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Influence of age on H reflex during upright standing

Baudry 2016

n = 94

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Influence of age on MEP during upright standing

Baudry 2016

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Increased contribution of corticospinal inputs

Corticospinal inputs Soleus motor neuron pool

  • +

 latency  Mechanical

  • utput

Muscle spindles afferent inputs

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Increased in plantar flexor activity during upright standing

Vandervoort and McComas, 1986 Billot et al. 2010

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Increased in muscle activation

Baudry et al. 2012 Billot et al. 2010 aEMG (% MVC)

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Increased corticomotoneuronal excitability

MEP MN Interneuron Corticospinal cells Corticomotoneuronal pathway

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Increased corticomotoneuronal excitability

MEP

Baudry et al. 2014

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Influence of muscle activation of H reflex

Baudry 2016

 Increase in muscle activity may alter proprioceptive signal

Proske and Gandevia 2012

n = 94

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Increase in muscle activation is associated with increased corticomotoneuronal drive and reduced relevance of group I afferents

Corticospinal inputs Soleus motor neuron pool

  • +

 latency  Mechanical

  • utput
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 Muscle activity  force Muscle spindles afferent inputs

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Increased coactivation

 combining high reflex gain (large H-reflex amplitude) and coactivation has an undesired effect on the steadiness of the motor output Dideriksen et al. 2015  Greater coactivation in older adults likely reduces the relevance of muscle afferent inputs Coactivation index: EMG-TA/EMG-SOL

Nagai et al. 2011

Coactivation index (%)

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Ageing changes the contribution of spinal and corticospinal pathway to control balance

Corticospinal inputs Soleus motor neuron pool

  • +

 latency  Mechanical

  • utput
  • +

 coactivation  Muscle activity  force Muscle spindles afferent inputs

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Training can modify age-related changes

Penzer et al. 2015

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Ageing changes the contribution of spinal and corticospinal pathway to control balance

Corticospinal inputs Soleus motor neuron pool

  • +

 latency  Mechanical

  • utput
  • +

 coactivation  Muscle activity  force Muscle spindles afferent inputs

 Those changes can likely be minimized by training