RAPID COMMUNICATION Response Variability and Timing Precision of Neuronal Spike Trains In Vivo

Reich, Daniel S., Jonathan D. Victor, Bruce W. Knight, Tsugiven stimulus, even while the response itself changes drayoshi Ozaki, and Ehud Kaplan. Response variability and timing matically. This behavior was found in every cell examined precision of neuronal spike trains in vivo. J. Neurophysiol. 77: in our study. A simple theoretical model for neuronal fir2836–2841, 1977. We report that neuronal spike trains can exhibit ing—the leaky or ‘‘forgetful’’ integrator (Knight 1972) — high, stimulus-dependent temporal precision even while the trialalso produces this sort of spiking behavior and provides a to-trial response variability, measured in several traditional ways, straight-forward resolution of the apparent paradox. remains substantially independent of the stimulus. We show that retinal ganglion cells and neurons in the lateral geniculate nucleus M E T H O D S (LGN) of cats in vivo display both these aspects of firing behavior, which have previously been reported to be contradictory. We deExperiments velop a simple model that treats neurons as ‘‘leaky’’ integrate-andfire devices and show that it, too, can exhibit both behaviors. We We recorded extracellularly the activity of lateral geniculate consider the implications of our findings for the problem of neural nucleus (LGN) neurons and their retinal inputs in anesthetized, coding. paralyzed cats (Kaplan et al. 1987). Experiments were performed on two male and one female adult cats. The behavior described in this paper was seen in all four retinal ganglion and LGN cells from