Cognitive impairment is associated with disrupted motor planning in older adults

BACKGROUND: Neurocognitive disorders are frequently accompanied by motor impairments that may precede overt cognitive decline. However, most motor markers remain coarse and do not disentangle global motor deterioration from disruptions of specific motor control processes. Motor planning, a process relying on both motor and cognitive resources, may be particularly vulnerable to cognitive impairment, yet has rarely been investigated using process-specific motor control frameworks. METHODS: We assessed motor planning abilities in 57 older adults, including cognitively impaired (CI; n = 27) and healthy (HA; n = 30) participants. Using a gravity-related motor planning paradigm, participants performed vertical arm movements requiring different interactions with gravitational torque. Directional asymmetries in movement kinematics were used as a process-specific proxy of motor planning. Movement smoothness was quantified using jerk-based measures as a complementary index of global motor execution. Movement duration was carefully controlled across groups and directions, and age effects were accounted for in the analyses. RESULTS: Movement duration did not differ between groups. Compared with HA participants, the CI group exhibited reduced directional asymmetries, indicating altered motor planning. Within the CI group, the magnitude of directional asymmetries was positively correlated with cognitive status, as assessed by the Mini-Mental State Examination. In contrast, although movement smoothness was globally reduced in CI participants, jerk-based measures were not associated with cognitive status after controlling for age and movement duration. CONCLUSION: These findings suggest that cognitive impairment in older adults is specifically associated with a disruption of motor planning processes rather than a uniform degradation of motor execution. By dissociating global motor deterioration from planning-related decompensation, this study highlights the value of process-specific motor control measures for understanding sensorimotor alterations in neurocognitive disorders and their potential relevance for early detection.