Introduction: Upper limb performance asymmetries between the dominant and non-dominant hands are a critical feature of human motor control. However, the neural mechanisms underlying these differences across a continuum of motor behaviors—from simple tapping to complex grasping—remain unclear. This systematic review synthesizes and characterizes the neural mechanisms of hemisphere-specific lateralization in the context of motor control across tasks.
Methods: This study was registered in the PROSPERO database (CRD42021286264). We conducted a systematic review synthesizing n=40 original neuroimaging studies spanning four categories of manual motor tasks in right-handed adults: 1) Finger Pressing/Tapping (n=20), 2) Continuous Precision (n=12), 3) Aiming (n=4), and 4) Grasping/Gripping (n=4). The analysis focused on key motor-related regions of interest (primary motor M1, supplementary motor, premotor, parietal, cerebellum) to identify the unique contributions of contralateral execution vs. ipsilateral support for dominant right hand (RH) and non-dominant left hand (LH) movement. Data were extracted to characterize ipsilateral vs. contralateral BOLD magnitude, structural asymmetry (fractional anisotropy in cerebello-cortical tract), and changes in effective [BP1] [KT2] connectivity.
Results: The synthesis supported functional asymmetries consistent with the complementary dominance hypothesis. The left hemisphere (contralateral to dominant RH) provided optimal control (speed and efficiency) across all tasks, exhibiting effector-independent dominance in planning areas (intraparietal sulcus, premotor) and specialized control for tasks sensitive to rate or complexity. RH control maximizes efficiency through the left hemisphere inhibiting the right hemisphere, including transcallosal suppression of M1 in the ipsilateral left hemisphere. Conversely, LH control is maintained through dynamics coupling that compensates for the right hemisphere’s specialization: LH execution requires enhanced interhemispheric coupling to the ipsilateral left hemisphere, which is evidenced by increased ipsilateral M1 and premotor activity[BP3] [KT4] . This coupling is vital for LH skill acquisition and performance and extends to subcortical loops, where the left hemisphere requires unique ipsilateral cerebello-cortical modulation for LH force precision.
Conclusion: Motor performance asymmetry is driven by the dynamic allocation of the optimal control specialization in the left hemisphere, in right-handed adults. The left hemisphere controls the dominant RH via efficient interhemispheric pathways while simultaneously enforcing ipsilateral inhibition. Conversely, non-dominant LH control is achieved by dynamically transmitting the specialized control signal from the left hemisphere via enhanced interhemispheric connections to the contralateral right hemisphere. This framework provides specific neuroanatomical targets for understanding and manipulating motor control mechanisms in neurorehabilitation.