What is the mirror neuron system? Methods Results ...

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Sir Charles Gairdner Hospital ... Licari M, Elliott C, Lay B, Williams J. Motor imagery ability and internal representation of movement in children with probable ...
A functional J.

1 Reynolds ,

J.

2 Billington ,

S.

1 Kerrigan ,

Study J.

3 Williams ,

C.

4 Elliott ,

A.

5 Winsor ,

L.

5 Codd ,

M.

5 Bynevelt ,

M.

1 Licari

1. University of Western Australia; 2. University of Leeds; 3. Victoria University; 4. Curtin University; 5. Sir Charles Gairdner Hospital

What is the mirror neuron system?

SUPERIOR TEMPORAL SULCUS (STS)

Imitation and motor imagery are primary modalities of learning motor skills. The mirror neuron system (MNS) is thought to play an integral role in this process, active when a person observes, imagines, or performs an action (1; Figure 1). The MNS has recently been hypothesised to contribute to the motor impairments seen in DCD (2-4) however, limited research has examined this system at a neurological level in this population (2-3).

Proposed main source of visual input during imitation and stores a representation of the action to be drawn upon during movement production.

This study aimed to extend previous fMRI research exploring MNS function in DCD (2) by investigating: 1. Imitation and motor imagery performance in children with and without DCD. 2. Brain activation patterns during action observation, motor imagery, action execution, and imitation tasks using fMRI. 3. Group differences in brain activation patterns during imitation and motor imagery.

Description of observed action projected to the IPL for coding of the motor description of the action and how to achieve it.

It was hypothesized that there would be decreased activation in the MNS of children with DCD, specifically in the pars opercularis of the IFG, the PMv, IPL and STS, most prominent during the imitation condition.

Methods

INFERIOR PARIETAL LOBULE (IPL)

VENTRAL PREMOTOR CORTEX, (PMv) INFERIOR FRONTAL GYRUS (IFG)

Inverse Model

Goal of the action is coded in the frontal mirror areas. Information is sent back to the STS.

Forward Model

Figure 1. Information flow within the mirror neuron system.

Participants Ten right handed boys with probable DCD (mean = 10.18 ± 1.34), and nine group age matched controls (mean age = 10.41 ± 1.17 years) participated. Children were considered to have probable DCD if they scored at or below the 16th percentile on the MABC-2 (5). A score of ≥ 25th percentile was used as a cut-off for controls. Children with pDCD had reduced performance on both imitation (6) and motor imagery (7) tasks outside the scanner (p < 0.05). Ethics approval was obtained from the UWA Human Ethics Committee (RA/4/1/6492).

Imaging MRI scans were acquired using a 3T Philips Magnetic Resonance Scanner with a 12-channel head coil. Anatomical images were acquired first (T1-weighted 3D FFE 160 slices 1 x 1 x 1 mm). Two eight minute functional MRI runs were undertaken. Participants performed an unlearned right handed finger adduction/abduction task during four conditions (Figure 2): observation (red circle), motor imagery (yellow circle), execution (green circle), imitation (green circle).

Figure 2. MRI scanner, and task and rest conditions.

Results MNS Activation? To explore whether the MNS was active during the task conditions, exploratory whole brain analyses with collapsed groups were conducted. Results revealed activation of MNS and other motor regions (cluster level correction p(FWE) < 0.05; Figure 3).

Group Comparisons

Figure 3. Main effect of motor imagery > rest (purple), execution > rest (dark blue), and imitation > rest (green). Cluster-level extent threshold of pFWE < 0.05; (N.B. fading represents depth; sky blue/teal represents overlap of execution > rest and imitation > rest contrasts).

Figure 4. Imitation condition: Controls > DCD (uncorrected, p < 0.001).

References

During the imitation condition, the control group were identified to have small clusters of increased activation in the bilateral thalamus (x = -14, y = -33, z = 11, k = 18; x = 6, y = -33, z = 15, x = 10, y = -35, z = 15, k = 29), right caudate (x = 20, y = -19, z = 21, k = 45; x = 13, y = -24, z = 8, k = 10) and right posterior cingulate (x = 15, y = -40, z = 11, k = 29; Talairach coordinates, uncorrected p < 0.001; Figure 4). No group differences were identified for the observation, motor imagery, or execution conditions.

Conclusions • Consistent with other fMRI research (8), comparisons of neural activation revealed minimal differences between controls and children with DCD. • The absence of between-group differences in MNS is consistent with the results from previous fMRI research by our group (2). • Reduced activation in the caudate, thalamus and posterior cingulate during imitation are consistent deficits in motor planning and execution (9). • Given the absence of differential activation patterns within MNS regions, it is likely that performance deficits observed behaviourally are not core deficits and are likely to stem from dysfunction of other neural networks that also underlie and support these processes. • Alongside differences in grey matter structure (10-11), reduced activation in planning and attention regions during imitation in children with pDCD may suggest dysfunction of motor planning and attentional processes.

(1) Iacoboni M, Dapretto M. The mirror neuron system and the consequences of its dysfunction. Nature Review Neuroscience. 2006;7:942-951. (2) Reynolds JE, Licari MK, Billington J, Chen Y, Aziz-Zadeh L, Werner J, Winsor AM, Bynevelt M. Mirror neuron activation in children with developmental coordination disorder: A functional MRI study. International Journal of Developmental Neuroscience. 2016; 47:309-319. (3) Reynolds JE, Thornton AL, Elliott C, Williams J, Lay BS, Licari MK. A systematic review of mirror neuron system function in developmental coordination disorder: Imitation, motor imagery, and neuroimaging evidence. Research in Developmental Disabilities. 2015;47:234-283. (4) Werner JM, Cermak SA, Aziz-Zadeh L. Neural correlates of developmental coordination disorder: the mirror neuron system hypothesis. Journal of Behavioral and Brain Science. 2012;2(2):258268. (5) Henderson SE, Sugden DA, Barnett AL. Movement Assessment Battery for Children - 2. Manual. 2nd ed. Sidcup, England: The Psychological Corporation; 2007. (6) Ayres AJ. Sensory Integration and Praxis Tests: SIPT manual. Los Angeles: Western Psychological Services; 1989. (7) Reynolds JE, Licari M, Elliott C, Lay B, Williams J. Motor imagery ability and internal representation of movement in children with probable developmental coordination disorder. Human Movement Science. 2015;44:287-298. (8) Brown-Lum M, Zwicker JG. Brain imaging increases our understanding of developmental coordination disorder: A review of literature and future directions. Current Developmental Disorders Reports. 2015;2(2):131-140. (9) Herrero MT, Barcia C, Navarro J. Functional anatomy of thalamus and basal ganglia. Child’s Nervous System. 2002;18(8):386-404. (10) Langevin LM, MacMaster FP, Dewey D. Distinct patterns of cortical thinning in concurrent motor and attention disorders. Developmental Medicine & Child Neurology. 2015;57(3):257-264. (11) Reynolds JE, Licari MK, Reid SL, Elliott C, Winsor AM, Bynevelt M, Billington J. Reduced relative volume in motor and attention regions in developmental coordination disorder: A voxel-based morphometry study. International Journal of Developmental Neuroscience, 2017;58:59-64.