Fig 1.
Experiment workflow in which CBI was measured before and after an intervention.
The intervention consisted of spinal manipulation or sham control (~5–10 minutes) and motor sequence learning (~15 minutes).
Table 1.
Neck pain characteristics reported as mean ± standard deviation for each group.
Fig 2.
Raw traces from representative participants from all three groups.
Here, CBI50 is depicted pre- and post-spinal manipulation or sham control and motor training, as relative to raw traces of M1 activation. Pre motor, prior to spinal manipulation/sham control and motor sequence acquisition; Post motor, following spinal manipulation/sham control and motor sequence acquisition.
Fig 3.
Mean CBI50 responses in each group.
(A) Mean CBI50 response in healthy controls before and after the combined intervention of sham control and motor sequence acquisition. (B) Mean CBI50 response in neck pain control group before and after the combined intervention of sham control and motor sequence learning. (C) Mean CBI response in spinal manipulation group before and after the combined intervention of spinal manipulation and motor sequence learning. Pre motor, prior to spinal manipulation/sham control and motor sequence acquisition; Post motor, following spinal manipulation/sham control and motor sequence acquisition. Error bars depict SEM. *P < 0.001.
Fig 4.
Stimulus-response curves for representative subjects.
(A-C) Stimulus-response curves relative to maximum stimulator output on the x-axis for representative subjects that were (A) healthy, (B) recurrent neck pain sham, and (C) recurrent neck pain manipulation. (D-F) Stimulus-response curves relative to CBI50 as shown on the x-axis for representative subjects that were (D) healthy, (E) recurrent neck pain sham, and (F) recurrent neck pain manipulation. Pre motor, prior to spinal manipulation/sham control and motor sequence acquisition; Post motor, following spinal manipulation/sham control and motor sequence acquisition.
Fig 5.
Relationship between CBI change and pain severity.
Participants that had greater pain disinhibited CBI more following manipulation (blue) (rs(12) = 0.7, P < 0.01), but not following sham control (red).
Fig 6.
Mean response time and accuracy pre- and post-motor acquisition.
(A) Healthy participants had marginally reduced response time and had no change to accuracy. (B) Neck pain sham control had moderate reduction to response time and dramatically improved accuracy. (C) Neck pain treatment dramatically reduced response time and had only marginal increase to accuracy. (D) All subjects demonstrated overall reduction to response time and accuracy from pre- to post-motor acquisition. Error bars depict 1 SEM. Pre, pre-motor acquisition; Post, post-acquisition. * P = 0.02–0.04; ** P = 0.005; *** P ≤ 0.001.