Saccade-vergence interactions in macaques. I. Test of the omnipause Multiply Model

Area of Science:

• Neuroscience
• Ophthalmology
• Vision Science

Background:

• Horizontal vergence eye movements adjust focus between distant and near objects.
• Saccades, rapid eye movements, transiently enhance vergence velocity.
• The OPN Multiply Model proposes saccadic disinhibition of vergence neurons causes this enhancement.

Purpose of the Study:

• To test the OPN Multiply Model's explanation for saccade-induced vergence enhancement in monkeys.
• To investigate the neural mechanisms underlying enhanced vergence velocity during saccades.

Main Methods:

• Electrophysiological recordings in monkeys performing vergence eye movements.
• Analysis of vergence velocity, saccade timing, and saccade peak velocity.
• Comparison of experimental data with predictions of the OPN Multiply Model.

Main Results:

• Vergence enhancement onset correlated with saccade onset and OPN pause.
• Vergence enhancement magnitude depended on saccade-vergence timing.
• Peak vergence enhancement velocity correlated with saccadic peak velocity, not OPN pause duration.
• Vergence enhancement exhibited a saccadic-like peak-velocity/size relationship.

Conclusions:

• The OPN Multiply Model is incompatible with the observed data on vergence enhancement during saccades.
• Alternative models are needed to explain the relationship between saccades and vergence velocity.
• The findings challenge the proposed role of OPNs in modulating vergence during saccadic eye movements.