Use of interrupted saccade paradigm to study spatial and temporal dynamics of saccadic burst cells in superior colliculus in monkey

Area of Science:

• Neuroscience
• Oculomotor control
• Primate neurophysiology

Background:

• Saccade-related burst neurons (SRBNs) in the superior colliculus (SC) exhibit spatially delimited movement fields and saccade-locked activity.
• The precise temporal coding of dynamic saccadic control signals by SRBNs and their role in spatial ensemble shifts remain unclear.
• Previous studies were limited by the stereotyped nature of natural saccadic eye movements.

Purpose of the Study:

• To quantitatively assess the temporal coding of dynamic saccadic control signals by SRBNs.
• To investigate the participation of SRBNs in organized spatial shifts of activity within the SC.
• To elucidate the role of SRBNs in the control of saccadic eye movements.

Main Methods:

• Recorded spatial and temporal dynamics of SRBNs in alert, behaving monkeys.
• Utilized an interrupted saccade paradigm with pulsatile electrical stimulation of the brainstem's omnipauser region.
• Simultaneously recorded SRBN activity in the SC during interrupted saccades.

Main Results:

• Electrical stimulation powerfully and rapidly suppressed SRBN discharge (average latency 3.8 ms).
• SRBN activity resumed just before the onset of the reinitiated saccade and continued during it.
• Resumed saccades were accurately made to the target location despite altered amplitude.

Conclusions:

• SRBN activity is dynamically modulated by brainstem stimulation during saccades.
• SRBNs participate in the temporal control of saccadic eye movements, including reinitiated movements.
• These findings support the role of SRBNs in encoding dynamic saccadic control signals.