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Loss of presynaptic inhibition for step initiation in parkinsonian individuals with freezing of gait
Author(s) -
Lira Jumes Leopoldino Oliveira,
Ugrinowitsch Carlos,
Coelho Daniel Boari,
Teixeira Luis Augusto,
LimaPardini Andrea Cristina,
Magalhães Fernando Henrique,
Barbosa Egberto Reis,
Horak Fay B.,
SilvaBatista Carla
Publication year - 2020
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jp279068
Subject(s) - parkinson's disease , h reflex , physical medicine and rehabilitation , gait , reflex , neuroscience , psychology , task (project management) , medicine , disease , management , economics
Key points Individuals with freezing of gait (FoG) due to Parkinson's disease (PD) have small and long anticipatory postural adjustments (APAs) associated with delayed step initiation. Individuals with FoG (‘freezers’) may require functional reorganization of spinal mechanisms to perform APAs due to supraspinal dysfunction. As presynaptic inhibition (PSI) is centrally modulated to allow execution of supraspinal motor commands, it may be deficient in freezers during APAs. We show that freezers presented PSI in quiet stance (control task), but they presented loss of PSI (i.e. higher ratio of the conditioned H‐reflex relative to the test H‐reflex) during APAs before step initiation (functional task), whereas non‐freezers and healthy control individuals presented PSI in both the tasks. The loss of PSI in freezers was associated with both small APA amplitudes and FoG severity. We hypothesize that loss of PSI during APAs for step initiation in freezers may be due to FoG.Abstract Freezing of gait (FoG) in Parkinson's disease involves deficient anticipatory postural adjustments (APAs), resulting in a cessation of step initiation due to supraspinal dysfunction. Individuals with FoG (‘freezers’) may require functional reorganization of spinal mechanisms to perform APAs. As presynaptic inhibition (PSI) is centrally modulated to allow execution of supraspinal motor commands, here we hypothesized a loss of PSI in freezers during APA for step initiation, which would be associated with FoG severity. Seventy individuals [27 freezers, 22 non‐freezers, and 21 age‐matched healthy controls (HC)] performed a ‘GO’‐commanded step initiation task on a force platform under three conditions: (1) without electrical stimulation, (2) test Hoffman reflex (H‐reflex) and (3) conditioned H‐reflex. They also performed a control task (quiet stance). In the step initiation task, the H‐reflexes were evoked on the soleus muscle when the amplitude of the APA exceeded 10–20% of the mean baseline mediolateral force. PSI was quantified by the ratio of the conditioned H‐reflex relative to the test H‐reflex in both the tasks. Objective assessment of FoG severity (FoG‐ratio) was performed. Freezers presented lower PSI levels during quiet stance than non‐freezers and HC ( P < 0.05). During step initiation, freezers presented loss of PSI and lower APA amplitudes than non‐freezers and HC ( P < 0.05). Significant correlations were only found for freezers between loss of PSI and FoG‐ratio ( r = 0.59, P = 0.0005) and loss of PSI and APA amplitude ( r = −0.35, P < 0.036). Our findings suggest that loss of PSI for step initiation in freezers may be due to FoG.