Aberrant connectivity of the lateralized readiness system in non-syndromic congenital mirror movements

Non-syndromic CMM has a complex phenotype. Abnormal corpus callosum and corticospinal tract processes are suggested mechanisms of the mirror movements. To further explore behavioural and neural phenotype(s) the present study tests the hypothesis that the response readiness network comprising supplementary motor area (SMA) and connections with motor cortex (M1) functions abnormally in CMM.

Twelve participants with (non-syndromic) CMM and a control group (n = 28) were tested on a probabilistic Go-NoGo task while electroencephalography (EEG) was recorded to assess possible group differences in lateralized readiness of voluntary hand movements together with measures of SMA-M1 functional connectivity.

The CMM group demonstrated delayed lateralized readiness and stronger functional connectivity between left-brain SMA-M1 regions. Connectivity strength was correlated with measures of behavioural performance but not with extent of mirroring.

Abnormalities in brain processes upstream of movement output likely reflect neurocompensation as a result of lifelong experience with mirroring in CMM.

These findings extend the known neural abnormalities in CMM to include brain networks upstream from those involved in motor output and raise the question of whether neurocompensatory plasticity might be involved.