Homeostatic plasticity in the primary motor cortex of patients with non-specific chronic low back pain
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1
Western Sydney University, School of Science and Health, Australia
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2
Aalborg University, Health Science and Technology, Denmark
Aims
Homeostatic Plasticity (HP) mechanisms are known to regulate and stabilise use-dependent cortical plasticity. Previous studies suggest use-dependent cortical plasticity is altered in individuals with non-specific chronic Low Back Pain (cLBP). However, no study has investigated the effects of cLBP on HP. Here, we investigated HP in individuals with non-specific cLBP compared with pain-free controls.
Methods
Fifty individuals participated with non-specific cLBP experiencing low [n=25; Visual Analogue Scores (VAS): 1.6 1.1] and moderate (n=25; VAS: 5.7 1.4) pain, as well as 25 age- and sex-matched healthy controls. Participants received a single block of excitatory transcranial direct current stimulation (tDCS) for 7-minutes in one session to confirm the existence of an excitatory response to tDCS. In a separate session, participants were exposed to two excitatory blocks of tDCS (7-min and 5-min separated by a 3 min rest period), to evaluate homeostatic responses to cortical over-excitation. Sessions were randomised and conducted one week apart. Transcranial magnetic stimulation induced motor evoked potentials (MEPs) were recorded from the First Dorsal Interosseous muscle before and after excitatory tDCS at baseline, and at 0, 10, 20 and 30-minutes follow-up.
Results
MEP amplitudes reflecting corticomotor excitability were increased at all time-points in all three groups (p<0.001) following 7-min of tDCS, confirming the existence of an excitatory response to this protocol. However, only healthy controls demonstrated reduced MEP amplitudes (p<0.05) as a homeostatic response. MEP amplitudes in the two pain groups either increased over time (low pain group; p<0.049), or remained static (moderate pain group; p=0.996) indicating homeostatic impairment.
Conclusions
These results demonstrate failure to stabilize excessive corticomotor excitability in the primary motor cortex of individuals with cLBP. This suggests impaired homeostatic mechanisms could contribute to maladaptive use-dependent plasticity in cLBP. Further research is required to determine the relationship between homeostatic plasticity and symptoms in cLBP.
Keywords:
homeostatic plasticity,
Primary motor cortex (M1),
non-invasive brain stimulation,
Corticomotor Excitability,
motor evoked potential (MEP)
Conference:
ASP2016 - The 26th Annual Meeting of the Australasian Society for Psychophysiology, Adelaide Australia, Adelaide,SA, Australia, 12 Dec - 14 Dec, 2016.
Presentation Type:
Oral Presentation
Topic:
Abstract (student award)
Citation:
Thapa
T,
Chipchase
L,
Graven-Nielsen
T and
Schabrun
S
(2016). Homeostatic plasticity in the primary motor cortex of patients with non-specific chronic low back pain.
Conference Abstract:
ASP2016 - The 26th Annual Meeting of the Australasian Society for Psychophysiology, Adelaide Australia.
doi: 10.3389/conf.fnhum.2016.221.00028
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Received:
10 Oct 2016;
Published Online:
05 Dec 2016.
*
Correspondence:
Mr. Tribikram Thapa, Western Sydney University, School of Science and Health, Sydney, Australia, t.thapa@westernsydney.edu.au
Dr. Lucinda Chipchase, Western Sydney University, School of Science and Health, Sydney, Australia, l.chipchase@westernsydney.edu.au
Dr. Thomas Graven-Nielsen, Aalborg University, Health Science and Technology, Aalborg,, Denmark, tgn@hst.aau.dk