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J Neurophysiol. 2014 Sep 15;112(6):1439-46. doi: 10.1152/jn.00225.2014. Epub 2014 Jun 18.

Operant conditioning of the soleus H-reflex does not induce long-term changes in the gastrocnemius H-reflexes and does not disturb normal locomotion in humans.

Author information

1
Helen Hayes Hospital, New York State Department of Health, West Haverstraw, New York; Program in Human Movement Science, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina;
2
Program in Human Movement Science, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Department of Health Professions, Medical University of South Carolina, Charleston, South Carolina;
3
Helen Hayes Hospital, New York State Department of Health, West Haverstraw, New York; Wadsworth Center, New York State Department of Health, Albany, New York; Department of Neurology, Neurological Institute, Columbia University, New York, New York; and Department of Biomedical Sciences, State University of New York, Albany, New York.
4
Helen Hayes Hospital, New York State Department of Health, West Haverstraw, New York; Wadsworth Center, New York State Department of Health, Albany, New York; Department of Neurology, Neurological Institute, Columbia University, New York, New York; and Department of Biomedical Sciences, State University of New York, Albany, New York a.kido.thompson@gmail.com.

Abstract

In normal animals, operant conditioning of the spinal stretch reflex or the H-reflex has lesser effects on synergist muscle reflexes. In rats and people with incomplete spinal cord injury (SCI), soleus H-reflex operant conditioning can improve locomotion. We studied in normal humans the impact of soleus H-reflex down-conditioning on medial (MG) and lateral gastrocnemius (LG) H-reflexes and on locomotion. Subjects completed 6 baseline and 30 conditioning sessions. During conditioning trials, the subject was encouraged to decrease soleus H-reflex size with the aid of visual feedback. Every sixth session, MG and LG H-reflexes were measured. Locomotion was assessed before and after conditioning. In successfully conditioned subjects, the soleus H-reflex decreased 27.2%. This was the sum of within-session (task dependent) adaptation (13.2%) and across-session (long term) change (14%). The MG H-reflex decreased 14.5%, due mainly to task-dependent adaptation (13.4%). The LG H-reflex showed no task-dependent adaptation or long-term change. No consistent changes were detected across subjects in locomotor H-reflexes, EMG activity, joint angles, or step symmetry. Thus, in normal humans, soleus H-reflex down-conditioning does not induce long-term changes in MG/LG H-reflexes and does not change locomotion. In these subjects, task-dependent adaptation of the soleus H-reflex is greater than it is in people with SCI, whereas long-term change is less. This difference from results in people with SCI is consistent with the fact that long-term change is beneficial in people with SCI, since it improves locomotion. In contrast, in normal subjects, long-term change is not beneficial and may necessitate compensatory plasticity to preserve satisfactory locomotion.

KEYWORDS:

learning; plasticity; rehabilitation; spinal cord; synergists

PMID:
24944216
PMCID:
PMC4137250
DOI:
10.1152/jn.00225.2014
[Indexed for MEDLINE]
Free PMC Article

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