Reliability of oculomotor command signals carried by individual neurons.

The responses of sensory neurons to repeated presentations of identical stimuli can be highly reproducible. Little is known about the reliability of the motor command signals carried by individual premotor neurons. We measured the variability in the interspike intervals of the high-frequency, saccade-related bursts generated by neurons in the pontine reticular formation. During movements having similar amplitudes and velocity profiles, the interspike intervals of the high-frequency component of the bursts are very similar. The low variability in interspike intervals cannot be attributed to a burst mode characterized by fixed interspike times. Different, but repeatable, burst patterns are observed when movements having approximately the same amplitude but different velocity profiles occur. These findings suggest that the discharge of a single pontine cell is strongly correlated with the activity of other pontine burst cells. Both the high temporal precision of the saccade-related bursts and the correlated activity of pontine burst cells reduce variability in the signals sent to the motoneuron pools and, thereby, contribute to the accuracy and precision of saccadic eye movements.