Speed, acceleration/deceleration and septal theta amplitude as a function of position on the maze.

A: Three-dimensional scatterplot rotated to a specific view showing the relationship between position on 140-cm maze (x-axis), speed (y-axis), and color-coded for theta amplitude. As can be seen, with increasing and maximal speeds (centered in the middle of the maze) theta amplitude increases. B (left): Same as A, but for acceleration in one direction (rat moving from left to right) as denoted by the black arrows on the x-axis. At high accelerations and high decelerations theta amplitude is low and increases in amplitude at less extreme accelerations. Gray star denotes high accelerations and low theta amplitude, while the black star denotes high decelerations and low theta amplitude. B (right): Two-dimensional histograms depicting the relationship between acceleration and theta amplitude (top) and deceleration and theta amplitude (bottom). C: Filtered theta signal (gray) and theta envelope (black) plotted along with speed (blue) and acceleration (red). As can be seen, there is a sharp reduction of the theta amplitude at extreme accelerations and decelerations, and is more pronounced at high decelerations, as represented by the three-dimensional scatter plot and two-dimensional histograms in B. Gray stars represent time points of maximal acceleration, while black stars represent points of maximal deceleration. D and E: Same as A and B, but for a non-septal electrode. (All theta envelope units = ×10−4; all count units = ×103).