Figure 7: Effects of MPH on rotational dynamics in motor cortex (monkey U, 6 mg/kg dose).

Rotational dynamics were found in neural data from 50ms pre- to 150ms post-neural movement onset by applying jPCA to projections into reach-condition-dependent components found using dPCA (see Methods). a) Example rotational dynamics from a representative placebo and MPH session. In this example, the initial conditions have been corrected to match across treatment, thus allowing easier comparison of the neural trajectory. Note that the dotted (MPH) trajectories make it farther along the rotation axis in the same amount of time, thus suggesting a higher frequency. Colors represent different reach targets. b) Rotation frequency across treatments. Distributions of rotation frequencies calculated from resampled data for each treatment condition. Orange: data from MPH sessions; blue: data from placebo sessions. Triangles mark distribution means. Frequency was calculated from the top 4 dimensions (see Methods). c) Rotation frequencies are independent of reach speed. The data for MPH and placebo were split into two groups, each containing either the slowest 10% of trials (black) or the fastest 10% of trials (red). The rotation frequency was computed separately for each group within each treatment. This procedure was repeated across all sessions. d) Deviation from ideal rotations across treatments. Deviation (square root of the sum of squared errors) of jPCA rotations from an ideal rotational structure with frequency and amplitude fit to the jPCA trajectories. Bootstrapped deviation distributions from resampled data for each treatment condition. Conventions as in b).