Frames of reference for saccadic command tested by saccade collision in the supplementary eye field

Area of Science:

• Neuroscience
• Ophthalmology
• Systems Neuroscience

Background:

• The supplementary eye field (SEF) is crucial for controlling eye movements.
• Understanding the reference frame used by the SEF for saccadic eye movements is essential for comprehending sensorimotor transformations.

Purpose of the Study:

• To investigate whether the SEF encodes saccadic eye movements in an oculocentric (eye-centered) or nonoculocentric (head/body-centered) frame of reference.
• To determine if different subregions within the SEF represent distinct reference frames.

Main Methods:

• Utilized the "saccade collision" test with electrical stimulation of the SEF in head-fixed monkeys.
• Mapped saccade trajectories across various fixation points to assess goal encoding.
• Calculated convergence indices to classify SEF sites as "convergent" or "nonconvergent".

Main Results:

• Found that "nonconvergent" SEF sites showed saccade trajectory compensation, indicating an oculocentric frame of reference.
• "Convergent" SEF sites exhibited minimal compensation, suggesting a nonoculocentric frame of reference.
• Identified a spatial segregation, with nonconvergent sites located rostral to convergent sites.

Conclusions:

• The SEF encodes saccade goals in at least two distinct frames of reference.
• Results suggest a rostrocaudal organization within the SEF for representing oculocentric and nonoculocentric saccade goals.