Modeling eye-head gaze shifts in multiple contexts without motor planning

Area of Science:

• Neuroscience
• Computational Biology
• Systems Neuroscience

Background:

• Gaze shifts involve coordinated eye and head movements for target acquisition and fixation.
• Existing models often lack integrated saccadic and fixation modes with switching mechanisms.

Purpose of the Study:

• To develop a unified computational model of gaze shift control incorporating eye and head movements.
• To explain observed gaze characteristics and provide novel predictions for neural circuits and behavior.

Main Methods:

• Implemented a model reduction approach to simplify parameters by lumping cerebellar effects.
• Ensured model topology aligns with known neuroanatomy and neurophysiology.
• Validated the model against experimental data from various contexts.

Main Results:

• The model replicates species- and subject-specific gaze characteristics with minor parameter adjustments.
• Demonstrated gaze movement to a target during fixation mode.
• Explained ocular compensation during saccades via vestibular nuclei projections.
• Identified two key nonlinearities driving gaze control.
• Attributed trajectory variations to neural dynamics, not planning.
• Accounted for "compensatory" slow phases post-semicircular canal plugging.

Conclusions:

• The proposed model provides a parsimonious explanation for complex eye-head coordination.
• It successfully simulates vestibulo-ocular reflex and pursuit nystagmus.
• The model predicts that eye-head and limb coordination can occur without explicit trajectory planning.