The oculomotor neural integrator uses a behavior-related coordinate system

Area of Science:

• Computational neuroscience
• Systems neuroscience
• Neurophysiology

Background:

• Coordinate systems are fundamental in understanding brain function, particularly in how neural networks represent spatial information.
• The oculomotor integrator, responsible for maintaining eye position, is constrained by Listing's law, implying a specific neural coordinate system.

Purpose of the Study:

• To investigate whether the oculomotor integrator explicitly represents coordinate systems and if they are tied to anatomical geometry.
• To test the hypothesis that the integrator's coordinate system aligns with Listing's plane due to behavioral constraints.

Main Methods:

• Developed a kinematically accurate model of a three-dimensional saccade generator with three mathematical integrators for eye position components.
• Simulated integrator failures to observe eye position drift patterns.
• Experimentally measured three-dimensional eye positions in Macaca fascicularis after inactivating the interstitial nucleus of Cajal (INC) using muscimol.

Main Results:

• Simulated and experimentally observed eye position drift after INC inactivation aligned with Listing's plane, not stereotaxic coordinates.
• Transformed data into a coordinate system aligned with Listing's plane eliminated extraneous horizontal drift.
• The direction of torsional drift and the resting eye position range strongly correlated with Listing's plane.

Conclusions:

• Integrator cell populations utilize an orthogonal, craniotopic coordinate system.
• This neural coordinate system is developmentally predisposed and aligned with Listing's plane.
• Findings challenge the notion of coordinate systems being mere byproducts of anatomy, suggesting explicit neural representation.