Fig. 1.

Set up and instantaneous discharge probability estimates. A light spot was presented in the center of the screen and was moved at a uniform velocity (15°/sec) toward the periphery while the cat was continuously fixating another central point. The onsets of the fixation point (FP) and stimulus point (SP) are shown in A. During the fixation task, the SP was moved toward the periphery, as illustrated inB. The FP and eye positions are presented inC. Cellular activities were recorded from two independent electrodes (D). Result of spike discrimination (E) is shown for a single stimulus presentation. After window discrimination, this train was classified as a single-unit activity, and the other was classified as a multiunit activity. In this study, the estimate of the instantaneous discharge probability (F) is the spike train (E), filtered with a 10 msec Gaussian kernel (filtered spike train). This measure is contrasted with the commonly used PSTH (G) calculated from 80 trials which, in this case, underestimates the discharge probability because the data were not stationary during the 80 trials, as in many experiments on awake animals.