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Neurobiol Learn Mem. 2014 Mar;109:178-92. doi: 10.1016/j.nlm.2013.12.016. Epub 2014 Jan 18.

Comparison of the classically conditioned withdrawal reflex in cerebellar patients and healthy control subjects during stance: 2. Biomechanical characteristics.

Author information

  • 1Institute of Physiology, University of Munich, Pettenkoferstr. 12, 80336 München, Germany. Electronic address: Dieter.Kutz@lrz.uni-muenchen.de.
  • 2Institute of Physiology, University of Munich, Pettenkoferstr. 12, 80336 München, Germany. Electronic address: thomas.kaulich@web.de.
  • 3Institute of Physiology, University of Munich, Pettenkoferstr. 12, 80336 München, Germany. Electronic address: w.foehre@web.de.
  • 4Department of Neurology, University of Duisburg-Essen, Hufelandstr. 55, 45122 Essen, Germany. Electronic address: Marcus.Gerwig@uk-essen.de.
  • 5Department of Neurology, University of Duisburg-Essen, Hufelandstr. 55, 45122 Essen, Germany. Electronic address: Dagmar.Timmann-Braun@uni-duisburg-essen.de.
  • 6Institute of Physiology, University of Munich, Pettenkoferstr. 12, 80336 München, Germany. Electronic address: f.kolb@lmu.de.

Abstract

This study addresses cerebellar involvement in classically conditioned nociceptive lower limb withdrawal reflexes in standing humans. A preceding study compared electromyographic activities in leg muscles of eight patients with cerebellar disease (CBL) and eight age-matched controls (CTRL). The present study extends and completes that investigation by recording biomechanical signals from a strain-gauge-equipped platform during paired auditory conditioning stimuli (CS) and unconditioned stimuli (US) trials and during US-alone trials. The withdrawal reflex performance-lifting the stimulated limb (decreasing the vertical force from that leg, i.e. 'unloading') and transferring body weight to the supporting limb (increasing the vertical force from that leg, i.e. 'loading')-was quantified by the corresponding forces exerted onto the platform. The force changes were not simultaneous but occurred as a sequence of multiple force peaks at different times depending on the specific limb task (loading or unloading). Motor learning, expressed by the occurrence of conditioned responses (CR), is characterized by this sequence beginning already within the CSUS window. Loading and unloading were delayed and prolonged in CBL, resulting in incomplete rebalancing during the analysis period. Trajectory loops of the center of vertical pressure-derived from vertical forces-were also incomplete in CBL within the recording period. However, exposing CBL to a CS resulted in motor improvement reflected by shortening the time of rebalancing and by optimizing the trajectory loop. In summary, associative responses in CBL are not absent although they are less frequent and of smaller amplitude than in CTRL.

Copyright © 2014 Elsevier Inc. All rights reserved.

KEYWORDS:

Center of vertical pressure; Cerebellum; Motor learning; Performance; Sequence of force peaks; Withdrawal reflex during stance

PMID:
24445111
[PubMed - in process]
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