Difference between visually and electrically evoked gaze saccades disclosed by altering the head moment of inertia.

Differences between gaze shifts evoked by collicular electrical stimulation and those triggered by the presentation of a visual stimulus were studied in head-free cats by increasing the head moment of inertia. This maneuver modified the dynamics of these two types of gaze shifts by slowing down head movements. Such an increase in the head moment of inertia did not affect the metrics of visually evoked gaze saccades because their duration was precisely adjusted to compensate for these changes in movement dynamics. In contrast, the duration of electrically evoked gaze shifts remained constant irrespective of the head moment of inertia, and therefore their amplitude was significantly reduced. These results suggest that visually and electrically evoked gaze saccades are controlled by different mechanisms. Whereas the accuracy of visually evoked saccades is likely to be assured by on-line feedback information, the absence of duration adjustment in electrically evoked gaze shifts suggests that feedback information necessary to maintain their metrics is not accessible or is corrupted during collicular stimulation. This is of great importance when these two types of movements are compared to infer the role of the superior colliculus in the control of orienting gaze shifts.

[1]  D. Robinson,et al.  The vestibulo‐ocular reflex during human saccadic eye movements. , 1986, The Journal of physiology.

[2]  J. Mcilwain Lateral spread of neural excitation during microstimulation in intermediate gray layer of cat's superior colliculus. , 1982, Journal of neurophysiology.

[3]  R. Douglas,et al.  Eye-head coordination in cats. , 1984, Journal of neurophysiology.

[4]  Christian Quaia,et al.  Distributed model of control of saccades by superior colliculus and cerebellum , 1998, Neural Networks.

[5]  D Guitton,et al.  Movement of neural activity on the superior colliculus motor map during gaze shifts. , 1991, Science.

[6]  J. Stahl,et al.  Amplitude of human head movements associated with horizontal saccades , 1999, Experimental Brain Research.

[7]  Philippe Lefèvre,et al.  Dynamic feedback to the superior colliculus in a neural network model of the gaze control system , 1992, Neural Networks.

[8]  L. Optican,et al.  Slow saccades in spinocerebellar degeneration. , 1976, Archives of neurology.

[9]  D. Munoz,et al.  Comparison of the discharge characteristics of brain stem omnipause neurons and superior colliculus fixation neurons in monkey: implications for control of fixation and saccade behavior. , 1998, Journal of neurophysiology.

[10]  R. Tomlinson Combined eye-head gaze shifts in the primate. III. Contributions to the accuracy of gaze saccades. , 1990, Journal of neurophysiology.

[11]  D. Guitton,et al.  Three-dimensional eye-head coordination during gaze saccades in the primate. , 1999, Journal of neurophysiology.

[12]  L. Optican,et al.  Model of the control of saccades by superior colliculus and cerebellum. , 1999, Journal of neurophysiology.

[13]  D. Sparks,et al.  Combined eye-head gaze shifts produced by electrical stimulation of the superior colliculus in rhesus monkeys. , 1996, Journal of neurophysiology.