Cover Picture: When the target of a hand movement jumps from one spatial position (yellow) to another (blue), the hand smoothly changes its original trajectory toward the first target and moves to the second one. The modulation of cell activity in the Superior Parietal Lobule is highly correlated and predicts the changes in hand position, speed, and movement direction. This relationship between parietal neural activity and hand kinematics stays at the core of online control of trajectory and provides the basis to understand the difficulty of parietal patients in updating intended movements. The activity of a parietal cell is shown as graded blue-yellow spike-density function, where each color is associated to a particular movement direction. The white thin curve represents the changes of hand speed relative to modulation of neural activity. The triangles on the x-axis indicate the moment of the first and second target's presentation, from left to right respectively. The pyramidal cell on the left is redrawn from the “Histologie du systém nerveux de l'homme et des vertébrés,” by Ramon Y Cajal, Instituto Ramon Y Cajal, Madrid 1972. See Archambault et al. 2009. Cortical mechanisms for online control of hand movement trajectory. The role of the posterior parietal cortex. Cereb Cortex 19(12): 2848-2864.
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