The myth of the 'unaffected' side after unilateral stroke: Is reorganisation of the non‐infarcted corticospinal system to re-establish balance the price for recovery?

► We studied the two corticospinal systems in chronic unilateral strokes and controls. ► We investigated motor cortex (EEG), spine/muscle (EMG) and their coherence (CMC). ► Bilateral symmetrical loss of beta power in EEG and EMG was found in strokes. ► EEG, EMG, CMC symmetry indices were similar to controls and correlated with recovery. ► Balance between the two systems is achieved at the expense of the unlesioned system.