A quantitative analysis of abducens motoneuron behavior during saccadic eye movements in the alert cat

The activity of identified abducens motoneurons has been recorded during spontaneous eye movements in the alert cat. Abducens motoneurons showed a burst of activity during saccades in the abducting direction. However, peak frequency during the burst was reached on the 4th-7th intervals. Instantaneous frequency of the first 5 intervals during the burst was linearly related to peak saccadic velocity and to peak frequency. Functional implications of reported findings are discussed in the text. These results favor the view that firing in abducens motoneurons during saccades is predetermined from the beginning of saccades, and do not provide evidence for possible modification of abducens motoneurons firing through internal feedback of motor error signals.