03180nas a2200277   4500008004100000022001400041245010400055210006900159260001200228300001100240490000800251520226600259653002102525653002902546653001102575653001702586653001302603653002102616653001202637653002102649653003802670100002502708700002202733700002402755856012302779       2023                        eng d  a1522-159800aThe human motor cortex contributes to gravity compensation to maintain posture and during reaching.0 ahuman motor cortex contributes to gravity compensation to mainta  c01/2023  a83-1010 v1293 a<p>The neural control of posture and movement is interdependent. During voluntary movement, the neural motor command is executed by the motor cortex through the corticospinal tract and its collaterals and subcortical targets. Here we address the question of whether the control mechanism for the postural adjustments at nonmoving joints is also involved in overcoming gravity at the moving joints. We used single-pulse transcranial magnetic stimulation to measure the corticospinal excitability in humans during postural and reaching tasks. We hypothesized that the corticospinal excitability is proportional to background muscle activity and the gravity-related joint moments during both static postures and reaching movements. To test this hypothesis, we used visual targets in virtual reality to instruct five postures and three movements with or against gravity. We then measured the amplitude and gain of motor evoked potentials in multiple arm and hand muscles at several phases of the reaching motion and during static postures. The stimulation caused motor evoked potentials in all muscles that were proportional to the muscle activity. During both static postures and reaching movements, the muscle activity and the corticospinal contribution to these muscles changed in proportion with the postural moments needed to support the arm against gravity, supporting the hypothesis. Notably, these changes happened not only in antigravity muscles. Altogether, these results provide evidence that the changes in corticospinal excitability cause muscle cocontraction that modulates limb stiffness. This suggests that the motor cortex is involved in producing postural adjustments that support the arm against gravity during posture maintenance and reaching. Animal studies suggest that the corticospinal tract and its collaterals are crucial for producing postural adjustments that accompany movement in limbs other than the moving limb. Here we provide evidence for a similar control schema for both arm posture maintenance and gravity compensation during movement of the same limb. The observed interplay between the postural and movement control signals within the corticospinal tract may help explain the underlying neural motor deficits after stroke.</p>10aElectromyography10aEvoked Potentials, Motor10aHumans10aMotor Cortex10aMovement10aMuscle, Skeletal10aPosture10aPyramidal Tracts10aTranscranial Magnetic Stimulation1 aHardesty, Russell, L1 aEllaway, Peter, H1 aGritsenko, Valeriya  uhttps://www.neurotechcenter.org/publications/2023/human-motor-cortex-contributes-gravity-compensation-maintain-posture00491nas a2200157   4500008004100000022001400041245006900055210006700124260001200191300001600203490000700219653002100226100002100247700001700268856004800285       2001                        eng d  a0028-387800aTaking sides: corticospinal tract plasticity during development.0 aTaking sides corticospinal tract plasticity during development  c11/2001  a1530–15310 v5710aPyramidal Tracts1 aWolpaw, Jonathan1 aKaas, J., H.  uhttp://www.ncbi.nlm.nih.gov/pubmed/11706084