Discharge Dynamics of Oculomotor Neural Integrator Neurons During Conjugate and Disjunctive Saccades and Fixation

• Published in: Journal of neurophysiology Vol. 90; no. 2; pp. 739 - 754
• Main Authors: Sylvestre, Pierre A, Choi, Julia T. L, Cullen, Kathleen E
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.08.2003
• Subjects: Action Potentials; Animals; Electrophysiology; Fixation, Ocular - physiology; Macaca mulatta; Neurons - physiology; Oculomotor Nerve - physiology; Saccades - physiology; Vestibular Nuclei - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00123.2003

Aerospace Medical Research Unit, Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada Submitted 10 February 2003; accepted in final form 26 March 2003 Burst-tonic (BT) neurons in the prepositus hypoglossi and adjacent medial vestibular nuclei are important elements of the neural integrator for horizontal eye movements. While the metrics of their discharges have been studied during conjugate saccades (where the eyes rotate with similar dynamics), their role during disjunctive saccades (where the eyes rotate with markedly different dynamics to account for differences in depths between saccadic targets) remains completely unexplored. In this report, we provide the first detailed quantification of the discharge dynamics of BT neurons during conjugate saccades, disjunctive saccades, and disjunctive fixation. We show that these neurons carry both significant eye position and eye velocity-related signals during conjugate saccades as well as smaller, yet important, "slide" and eye acceleration terms. Further, we demonstrate that a majority of BT neurons, during disjunctive fixation and disjunctive saccades, preferentially encode the position and the velocity of a single eye; only few BT neurons equally encode the movements of both eyes (i.e., have conjugate sensitivities). We argue that BT neurons in the nucleus prepositus hypoglossi/medial vestibular nucleus play an important role in the generation of unequal eye movements during disjunctive saccades, and carry appropriate information to shape the saccadic discharges of the abducens nucleus neurons to which they project. Address for reprint requests: K. E. Cullen, McIntyre Medical Research Bldg, Rm 1220, 3655 Prom. Sir William Osler, Montreal, Quebec, H3G 1Y6, Canada (E-mail: kathleen.cullen{at}mcgill.ca ).