Activity in deep intermediate layer collicular neurons during interrupted saccades.

Area of Science:

• Neuroscience
• Oculomotor control

Background:

• The superior colliculus (SC) plays a role in controlling eye movements, specifically saccades.
• Understanding how the SC processes movement commands during perturbations is crucial for explaining accurate motor control.

Purpose of the Study:

• To investigate the activity of deep intermediate layer neurons in the superior colliculus during saccades interrupted by brainstem omnipause neuron (OPN) stimulation.
• To determine if these neurons maintain their discharge during interruption, potentially serving as a memory trace for intended movements.

Main Methods:

• Recorded neuronal activity in the deep intermediate layers of the monkey SC during saccades.
• Interrupted ongoing saccades using electrical stimulation of the OPN region.
• Quantified the reduction in neuronal activity during saccade interruption compared to non-interrupted saccades.

Main Results:

• Approximately 70% of deep intermediate layer neurons showed a significant reduction (≥30%) in activity during saccade interruption.
• About 60% of recorded neurons exhibited discharge prolongation that matched the increased saccade duration during interruption.
• 30% of neurons showed minimal to no change in activity during OPN stimulation.

Conclusions:

• The majority of SC deep intermediate layer neurons do not maintain activity during saccade interruption, suggesting the SC alone may not store a precise memory of the intended saccadic goal.
• The temporal modulation of neuronal discharge, matching saccade duration, indicates dynamic feedback of saccadic motion to the SC.
• A subset of unperturbed neurons might contribute to saccade accuracy mechanisms during movement perturbations.