Directional Tuning in Frontoparietal Ensemble during Different Modes of Operation in Task 1

<div><p>(A–D) Directional tuning during pole control (A), brain control with arm movements (tuning assessed from cursor movements) (B), brain control without arm movements (tuning assessed from cursor movements) (C), and brain control with arm movements (tuning assessed from pole movements) (D). In each of the color-coded diagrams (red shows high values and blue low values; see color scale), the rows depict normalized directional tuning for individual cells. Because of the high directional tuning values of some cells (e.g., that shown in [H]), a color scale limit was set at 0.3 to allow color representation of the largest possible number of cells. Each tuning curve contains eight points that have been interpolated for visual clarity. Correspondence of tuning patterns under different conditions has been quantified using correlation coefficients (shown near lines connecting the diagrams). The highest correspondence was between tuning during pole control and brain control with arm movements. A much less similar pattern of direction tuning emerged during brain control without arm movements. Polar plots near each diagram show average directional tuning for the whole neural ensemble recorded. They indicate an average decrease in tuning strength and shifts in the preferred direction of tuning as the operation mode was switched from pole to brain control. Spread of preferred directions (90° corresponds to uniformly random distribution) is indicated near each polar plot.</p> <p>(E–G) Scatterplots comparing DTD (maximum minus minimum values of tuning curves) during pole control versus brain control with and without arm movements. DTD during brain control was consistently lower than during pole control. This effect was particularly evident during brain control without arm movements.</p> <p>(H–J) Changes in directional tuning for individual neurons under different conditions. Blue shows pole control; red, brain control with arm movements (tuning assessed from pole movements); and green, brain control without arm movements. The first illustrated cell (H) was tuned only when the monkey moved its arm, more so during pole control. The second cell (I) had similar tuning during all modes of operation, but tuning depth was the highest for pole control and the lowest for brain control without arm movements. The third cell (J) was better tuned during brain control.</p>