Ensemble Encoding of Gripping Force, Plasticity of Directional Tuning, and Neuronal Contribution to Model Performance during Learning to Control the BMIc for Reaching and Grasping

<div><p>(A) Perievent time histograms (PETHs) in task 2 for the neuronal population sampled in monkey 1. The plots on top are color-coded (red shows high values; blue, low values). Each horizontal row represents a PETH for a single-neuron or multiunit activity. PETHs have been normalized by subtracting the mean and then dividing by the standard deviation. PETHs are aligned on the gripping force onset (crossing a threshold). Plots at the bottom show the corresponding average traces of gripping force. Note the general similarity of PETHs in pole (left) and brain (right) control in this relatively easy task. Cortical location of neurons is indicated by the bar on the top left. Note the distinct pattern of activation for different areas.</p> <p>(B) Changes in the mean contribution of neurons from different cortical areas to model predictions during training of monkey 1 in task 2.</p> <p>(C) Increases in directional tuning for six cortical areas during training in pole control in task 3.</p> <p>(D and E) Increases in neuronal contribution to linear models predicting hand position (blue), hand velocity (red), and gripping force (black) during learning task 3 in both monkeys.</p> <p>(F and G) Representative robot trajectories and gripping force profiles in an advanced stage of training in task 3 during both pole and brain control. The bottom graphs show trajectories and the amount of the gripping force developed during grasping each virtual object. The dotted vertical lines in the panels indicate the end of reach phase and the beginning of grasp phase. Note that during both modes of BMIc operation, the patterns of reaching and grasping movements (displacement followed by force increase) were preserved.</p>