Fig. 3.
Rapid readout of choice responses. A: trackball position data. The trackball position record allows for high-resolution reconstruction of the animal's motor response. Ball movement trajectories for 4 example trials are shown with respect to auditory stimulus onset. Choices are registered when the trackball has rotated by 50° in either direction (shown as 26 mm along the ball circumference with respect to the position at trial start). B: timing of paw movement responses. Variability in ball position was calculated for the 1st 50 ms following auditory stimulus onset of 10,575 posttraining trials of 3 mice. The SD of position during this prereaction period was 1.65 mm. The duration of paw sweeps was considered during the period of fixation from ±3.3 mm (2 SD, gray dotted lines in A) to the ±26-mm decision boundary (black dotted lines) as a measure of the speed with which the mice operated the ball to report their decisions. Trials in which a mouse moved 6.5 mm in 1 direction and ultimately responded in the opposite direction were considered decision-reversal trials (Fig. 6) and omitted from this analysis. Mean response movement duration was 189 ms.