Fig. 2.

Representative neuron and STTF analysis. (A) Movement angle tuning curve, plotting firing rate as a function of movement angle measured at zero lag time. The tuning curve was well fit by a cosine model (R² = 0.92). (B) Diagram describing space–time tuning analysis. Neural activity was sampled from the middle of the movement period, and movement angle was sampled across the entire movement period, from movement onset to the time the cursor entered the target zone. This sampling scheme allowed each firing-rate sample to be paired with angle samples at all possible lag times considered. (C) Movement angle STTF. A contour plot shows the average firing rate of a cell that occurred for different movement angles measured over a range of lag times (−120 ms ≤ τ ≤ 120 ms) relative to the firing rate. (D) Movement angle TEF and corresponding goal-angle TEF, where mutual information between firing rate and movement angle is plotted as a function of lag time. The firing rate contained the most information about the movement angle at an optimal lag time of 0 ms. All error bars denote 95% confidence intervals. Because the target was stationary during each trial (e.g., goal angle did not change during a trajectory), the goal-angle information was approximately constant across lag time. The dashed lines denote surrogate TEFs, for both movement (red-dashed) and goal (green-dashed) angles, that were derived from surrogate spike trains and actual angles. Note that there is no temporal tuning structure in the surrogate movement-angle TEF.