Spatial transformations between superior colliculus visual and motor response fields during head-unrestrained gaze...

Area of Science:

• Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• The superior colliculus (SC) is crucial for generating rapid eye movements.
• Previous research indicated SC visuomotor activity encodes target position relative to the eye (Te) during immediate gaze shifts.
• The spatial coding of temporally separated visual and motor responses in the SC remains unclear.

Purpose of the Study:

• To investigate whether temporally separated visual and motor responses in the SC utilize different spatial codes.
• To determine if the SC performs a target-to-gaze transformation during head-unrestrained gaze shifts with delayed responses.

Main Methods:

• Two monkeys performed head-unrestrained gaze shifts with variable post-stimulus delays (400-700 ms).
• 3D eye and head orientations were recorded to dissociate frames of reference (eye, head, space).
• 2D response field data were fitted against multiple spatial coding models using a statistical method.

Main Results:

• Visual responses in the SC population (n=48) significantly preferred target-relative-to-eye (Te) coding.
• Motor responses in the SC population (n=43) significantly preferred final gaze position coding, eliminating the Te model.
• Visuomotor neurons showed a significant shift from Te coding in visual responses to gaze-centered coding in motor responses.

Conclusions:

• SC response fields are gaze-centered.
• A target-to-gaze transformation occurs between visual and motor responses within the SC.
• Visuomotor transformations can happen within single neurons and brain structures, even within the same reference frame.