Superior colliculus inactivation causes stable offsets in eye position during tracking.

Area of Science:

• Neuroscience
• Oculomotor control
• Primate vision

Background:

• The primate superior colliculus (SC) is traditionally viewed as having two distinct motor zones: a peripheral zone for saccades and a central zone for fixation.
• An alternative hypothesis suggests the SC topography represents a single map of behaviorally relevant goal locations.

Purpose of the Study:

• To test the interpretation that the SC forms a single map of goal locations rather than distinct motor zones.
• To investigate the role of the SC's topographic map in gaze control during complex tracking tasks.

Main Methods:

• Temporary inactivation of neurons in the central SC while primates tracked the invisible midpoint between two moving stimuli.
• Analysis of eye position offsets during tracking and assessment of saccade, smooth pursuit, and fixation abilities.

Main Results:

• Inactivation of the central SC, representing the inferred goal, caused stable eye position offsets during tracking.
• These offsets were not due to deficits in saccade generation, suppression, smooth pursuit, or fixation.
• The magnitude of the gaze offset correlated with the eccentricity of the inactivated SC site and spatial uncertainty of the goal.

Conclusions:

• Gaze control relies on the balanced activity across a map of goal locations within the SC.
• Focal inactivation of neurons representing a behavioral goal leads to a biased estimation of the target location.
• The SC topography is best understood as a unified map of behaviorally relevant goal locations.