ProprioceptionRelated Evoked Potentials - PowerPoint PPT Presentation

Title: ProprioceptionRelated Evoked Potentials


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Proprioception-Related Evoked Potentials

• Presented by
• Efrat Barak

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Objectives

• The objectives of this work are
• To introduce Proprioceptive Evoked Potentials
  (PEPs) and their stimulation, recording, and
  analysis techniques.
• To discuss the differences between PEPs and
  sensory evoked potentials (SEPs) that are
  elicited by electrical nerve stimulation.

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What Are Proprioceptive Evoked Potentials?

• Proprioception is sensing the body,
• i.e. gathering information about
• The bodys position in space
• Active and passive movements
• Force that is applied by the body
• Such data is collected by receptors of the
  somatosensory system, named proprioceptors, which
  report on stretching of muscles and angles of
  joints. For example, muscle spindles and Golgi
  tendon organs are proprioceptors.
• Due to independent studies of EPs related to
  proprioception, a number of different terms have
  emerged in this field

Arnfred et al., 2000 Bear et al., 2001
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Termination

• The most common terms are
• Proprioceptive Evoked Potentials (PEPs) are
  potentials evoked by addition of weight to a hand
  held load. Arnfred, et al., 2000
• Proprioceptive Event Related Potentials (PERPs)
  are potentials evoked by a stimulation similar to
  the former one, but with an oddball paradigm
  Arnfred, 2005
• Proprioception-related evoked potentials are
  potentials evoked by passive body movements
  Seiss et al., 2002
• For convenience, the term Proprioceptive Evoked
  Potentials (PEPs) will be used here to describe
  all potentials evoked by stimulation of
  proprioceptors, e.g. EPs evoked by active or
  passive movements. Notice that this does not
  include potentials evoked by electrical
  stimulation.

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Example PEPs Related to Finger Movement

• Bötzel et al. 1997 studied potentials evoked by
  finger movement in 11 healthy subjects.
• Post-movement potentials were evoked by three
  stimulation methods
• The subject actively moved his right middle
  finger to a given position (active movement).
• The finger was passively stretched by a
  technician that pulled a string that was tapped
  to the finger (passive movement). The finger
  was extended to the same position as in (1), in a
  comparable velocity.
• The median nerve was electrically stimulated,
• and the somatosensory evoked potentials
• (SEPs) were recorded.

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Example PEPs Related to Finger Movement

• During stimulation, EEG was recorded from the
  scalp using the 10-20 system.
• Source analysis was performed using
• the BESA program.
• Results
• The active and passive EPs were very similar, and
  both included an N2/P2 complex at about 80ms
  after stimulus onset (Fig. 1), with stronger P2
  in the passive case.
• In the SEPs, N20/P20 complex was identified (data
  not shown).

Fig. 1. Thick line recording from electrode 3.
Thin line finger acceleration trace.
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Example PEPs Related to Finger Movement

• The dipoles of the N2/P2 and the N20/P20
  complexes were attributed to the same area in the
  contralateral hemisphere, but differed in dipole
  orientation (Fig. 2)
• SEPs N20/P20 dipole pointed anterior-medially.
• Active and passive N2/P2 dipoles pointed
  posteriorly.

Fig. 2. Average dipole locations. Back - active
movement N2/P2 dipole. Light grey - passive
movement N2/P2 dipole. Dark grey - median nerve
SEP N20/P20 dipole. The angular part signals the
range of orientations of the positive dipoles
ends.
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Example PEPs Related to Finger Movement

• Discussion Because the EPs of the active and
  passive stimuli were very similar, they must be
  purely somatosensory (a motor component would
  have appeared in the active condition only).
• What is the origin of this somatosensory
  information?
• Cutaneous afferents and joint afferents are ruled
  out because they usually do not report joint
  position.
• Golgi tendon organs are also not an option,
  because they are not modulated by passive joint
  movements.
• Primary muscle spindle afferents of the forearm
  are the best candidates.
• By contrast, it has been established that the
  median nerve SEPs originates in cutaneous and
  joint receptors, and has very little contribution
  from muscle spindles Seiss et al. 2003.

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Example PEPs Related to Finger Movement

• Conclusion The N2/P2 complex arises from
  cerebral processing of proprioceptive information
  sent from muscle spindles to the brain.
  Therefore, the potentials elicited by passive and
  active movements are PEPs.
• Interestingly, the dipole analysis indicated that
  the proprioceptive information arrives to S1.
  This result will later be compared to those of
  other researches.

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Example II PEPs Related to Wrist Movement

• Arnfred et al. 1999 studied potentials evoked
  by a change of load that the subject held (Fig
  3).

• Stimulation linear increment of the load from
  400g to 480g , in steps of 20g in 10ms. The
  maximal load (480g) was maintained for 100ms. The
  stimulus was described as carrying a basket of
  apples when another apply is suddenly thrown into
  it.

Fig. 3. Experimental set-up

• EEG was recorded from 10 right-handed subjects
  using the 10-20 system

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Example II PEPs Related to Wrist Movement

• Results the major components of the EPs were
  (Fig. 4)
• Contralateral parietal waves P70\P190 at C3
• Frontal N70 wave at Fz
• P100 wave at Cz

• Discussion
• The pattern of very close frontal and parietal
  activation with reverse polarities resembles the
  PEPs of passive movements that were recorded by
  Bötzel et al. their data is not shown, and is
  significantly different from median nerve SEPs.

Fig. 4. Grand average of the EPs. Arrows mark
stimulus onset.
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Example II PEPs Related to Wrist Movement

• Moreover, the stimulus was perceived as applied
  force, i.e. neither tactile nor passive movement.
• Conclusion A brisk change of hand held load
  elicits PEPs with intermediate latency.
• In a later work, Arnfred 2005 studied the EPs
  elicited by a similar method, using an oddball
  paradigm. The subjects had to recognize the type
  of stimulus (frequent 40g / rare 100g) and
  count the oddball stimuli.
• This study showed that P100 of the two stimuli
  hardly differed, while later components were
  influenced by the context. Since P100 is related
  to specific processing in S2 cortex, the author
  concluded that the proprioceptive stimulus is
  processed within the first 100ms.

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Sensitivity of PEPs to Movement Parameters

• Seiss et al. 2002 studied the influence of
  movement parameters on PEPs elicited by passive
  movements.
• Stimulation was performed by a robot that
  imposed four types of passive finger movements
  (Fig 5)
• Extension to 15mm
• Extension to 25mm
• Flexion to 15mm
• Flexion to 25mm
• During stimulation, EEG was recorded
• using the 10-20 system. Additionally,
• the authors recorded median nerve
• SEPs elicited by electrical stimulation.

Fig. 5. The robot that imposed passive finger
movements. Seiss et al., 2003
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Sensitivity of PEPs to Movement Parameters

• Results
• All PEPs elicited by the four passive movement
  stimuli were similar, with a frontal negative
  wave measured at electrode FC1 at about 90ms
  (denoted N90).
• The four PEPs differed only in the wave duration
  N90 was about 30ms longer for 25mm stimuli than
  for 15mm stimuli. Movement direction did not
  matter (Fig. 6).
• This prolongation was roughly
• proportional to the difference
• between the movement durations.
• The SEP showed the well known
• N20/P20 pattern.

Fig. 6. PEP grand average. Solid line 15mm
stimulus, dashed line 25mm stimulus.
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Sensitivity of PEPs to Movement Parameters

• Source analysis yielded a single dipole for each
  PEP. The dipoles were in close proximity, and
  were anterior to the source of the SEP.
• Moreover, the analysis showed that the PEPs are
  generated in the motor cortex.
• Conclusion
• The authors suggested the following longer
  movements may give rise to contributions of other
  neuronal populations to the PEP, which are not
  revealed in PEPs elicited by short movements.

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Conclusion PEPs Features

• Several corollaries can be made from the
  described studies
• PEPs reflect the arrival and processing of
  proprioceptive information at the cortex.
• PEPs can be elicited by
• Active movements
• Passive movements
• Weight lifting
• Muscle stretching (which was not discussed here)
• However, electrical stimulation elicits SEPs, not
  PEPs.
• It has been recently suggested that the first
  100ms of PEPs reflects processing of the
  proprioceptive stimulus, and later components are
  changed by the context.

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Conclusion PEPs Features

• The pattern of PEPs
• Comparing the described studies indicates that
  PEPs are usually characterized by a frontal
  negative component. The latency of this component
  varies between different experiments, probably
  due to differences in the stimulation techniques
  and the body part that is moving.
• Passive and active movements yield PEPs that are
  very similar, both in latencies and in
  amplitudes.
• While a number of studies concluded that PEPs are
  generated in the sensory cortex, a recent study
  indicated that PEPs also have contributions from
  the motor cortex.

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Comparison of PEPs and Electrically Evoked SEPs

• Origin PEPs reflect input from muscle spindle
  afferents only. On the contrary, median nerve
  SEPs reflect inputs from cutaneous afferents, as
  well as negligible inputs from muscle spindle
  afferents. Practically, it can be assumed that
  PEPs and SEPS reflect different inputs Seiss et
  al., 2003.
• Pattern The primary component of PEPs has a
  frontal-negative distribution, while the N20/P20
  component of the median nerve SEP has a
  parietal-negative/frontal-positive distribution.
• Cortical generator N2/P2 components of PEPs are
  generated in the sensorimotor cortrex, and their
  source is 7-10 mm anterior to the source of
  N20/P20 complex of the median nerve SEPs.

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The Benefit in PEPs Research

• Investigation of PEPs seems to hold promise in
  two fields
• Movement disorders. analysis of PEPs isolates
  information about the proprioceptive feedback
  that exists in the sensory-motor loop. Thus, PEPs
  investigation may improve our understanding of
  movement disorders such as Huntingtons disease
  and Parkinsons disease.
• Neuropsychiatric disorders. Since the perception
  of myself is established on integration of
  proprioceptive and sensory information, PEPs can
  be utilized for investigating neuropsychiatric
  disorders, e.g. schizophrenia.

Arnfred, 2005 Seiss et al., 2003
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References

• Arnfred, S., Chen, A. C., Eder, D., Glenthoj, B.,
  Hemmingsen, R. (2000) Proprioceptive evoked
  potentials in man cerebral responses to changing
  weight loads on the hand. Neurosci Lett, 288,
  111-4.
• Arnfred, S. M. (2005). Proprioceptive event
  related potentials gating and task effects. Clin
  Neurophysiol, 116, 849-60.
• Bear, M. F., Connors, B. W., Paradiso, M. A.
  (2001) Neuroscience Exploring the brain.
  Lippincott, Williams, Wilkins, Baltimore MD,
  Chapter 13.
• Bötzel, K., Eceker, C., Schulze, S. (1997)
  Topography and dipole analysis of reafferent
  electrical brain activity folllowing the
  Breitschaftsponttial. Exp. Brain Res., 114,
  352-361.
• Seiss, E., Hesse, C.W., Drane, S., Oostenveld,
  R., Wing, A.M., Praamstra, P., (2002)
  Proprioception-related evoked potentials origin
  and sensitivity to movement parameters.
  Neuroimage, 17(1) 461-8.
• Seiss, E., Praamstra, P., Hesse, C.W., Rickards,
  H. (2003). Proprioceptive sensory function in
  Parkinsons disease and Huntingtons disease
  evidence from proprio-ception-related EEG
  potentials. Exp. Brain Res., 148, 308-319.