Experimental setup.

<p>Examples of photographs of the setup presented to the subjects during the a. motor imagery (MI), and b. visual imagery (VI) tasks. Both photographs show a whiteboard with circle targets in the middle and a black line with the red dot from the laser (highlighted here) in between. During MI trials, a balance board is present in front of the whiteboard. During VI trials, a blue carpet replaces the balance board. In these examples, the trajectory length is long (80% of subjects' maximal sway) and the target size is large (8 cm of diameter); c. Time course of motor imagery trials. During each trial, after a short inspection of the photo on display, the subjects closed their eyes and imagined standing on the balance board. The subjects were asked to press a button with the index finger of their right hand to signal that they had started imagining swaying on the balance board. The subjects were asked to press the button again when they imagined the balance board was back to the starting position, after having aimed the laser dot at both targets. Following the second button press, a fixation cross was presented on the screen and the subjects could open their eyes. The duration of the inter-trial interval (ITI) was 3–6 s.</p

Behavioural results.

<p>Trial durations across tasks and conditions. <b>A</b>. Trial duration measured in each task [dynamic balance (DB), motor imagery (MI) and visual imagery (VI)]; <b>B</b>. Trial duration measured for each trajectory lengths within each task [short (60% of subjects' maximal sway) and long (80% of subjects' maximal sway)]; <b>C</b>. Trial duration measured for each target size within each task [large (8 cm) and small (2 cm)], Data represent mean ± SEM; <b>D</b>. Average r2 of the correlation between trial duration and ID for each of the different tasks (post hoc comparison of r2 across the different tasks). Data represent mean ± SD; * indicates p<0.05.</p

Brain regions activated during motor imagery of dynamic balance.

<p>A. Cerebral activity during motor imagery of balance. Statistical parametric map (SPM) of increased activity in the supplementary motor area (red), the dorsal premotor cortex (pink), the middle cingulate cortex (orange), the superior parietal lobule (cyan), the thalamus (green), the putamen (yellow) and the cerebellum (purple), during MI compared to VI [corrected for multiple comparisons (p<0.05) using family wise error (FWE)], superimposed on a 3D rendered brain (upper part) and on axial sections (lower part). B. Putamen activity; a. β values as a function of Task; b. Relationship between behavioral (imagery durations) and neural (β values) changes as a function of Task. Subject-by-subject variance in imagery durations was not correlated with the neural Task-related effects for both the MI (putamen: r = 0.025, p = 0.917) and VI tasks (putamen: r = 0.248, p = 0.291). C. Supplementary motor area activity; a. β values as a function of Task; b. Relationship between behavioral (imagery durations) and neural (β values) changes as a function of Task. Subject-by-subject variance in imagery durations was not correlated with the neural Task-related effects for both the MI (SMA: r = -0.062, p = 0.793) and VI tasks (SMA: r = 0.254, p = 0.279).</p

Comparison of gait and dynamic balance related activations in the mesencephalon.

<p>Statistical parametric map (SPM) of differential activity between motor imagery of gait (blue) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091183#pone.0091183-Cremers1" target="_blank">[9]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091183#pone.0091183-Snijders1" target="_blank">[12]</a> and motor imagery of balance (red).</p

Stereotactic coordinates of the local maxima activated in the contrast “MI>VI”.

<p>Results are corrected for multiple comparisons across the whole brain (FWE<0.05). Stereotactic coordinates are reported in MNI (Montreal Neurological Institute) space. Details on the anatomical and functional labeling can be found in the Results section. L = left; R = right; Funct = Functional.</p

Using motor imagery to study the neural substrates of dynamic balance

Contains fulltext : 126885.pdf (publisher's version ) (Open Access)This study examines the cerebral structures involved in dynamic balance using a motor imagery (MI) protocol. We recorded cerebral activity with functional magnetic resonance imaging while subjects imagined swaying on a balance board along the sagittal plane to point a laser at target pairs of different sizes (small, large). We used a matched visual imagery (VI) control task and recorded imagery durations during scanning. MI and VI durations were differentially influenced by the sway accuracy requirement, indicating that MI of balance is sensitive to the increased motor control necessary to point at a smaller target. Compared to VI, MI of dynamic balance recruited additional cortical and subcortical portions of the motor system, including frontal cortex, basal ganglia, cerebellum and mesencephalic locomotor region, the latter showing increased effective connectivity with the supplementary motor area. The regions involved in MI of dynamic balance were spatially distinct but contiguous to those involved in MI of gait (Bakker et al., 2008; Snijders et al., 2011; Cremers et al., 2012), in a pattern consistent with existing somatotopic maps of the trunk (for balance) and legs (for gait). These findings validate a novel, quantitative approach for studying the neural control of balance in humans. This approach extends previous reports on MI of static stance (Jahn et al., 2004, 2008), and opens the way for studying gait and balance impairments in patients with neurodegenerative disorders.11 p