Multielectrode evidence for spreading activity across the superior colliculus movement map

Area of Science:

• Neuroscience
• Ophthalmology
• Systems Neuroscience

Background:

• The monkey superior colliculus (SC) contains maps for visual input and motor output.
• Previous studies inferred activity spread within the SC from averaged data across multiple saccades.
• The precise spatiotemporal dynamics of SC activity during individual saccades were not well understood.

Purpose of the Study:

• To directly observe and quantify the spread of neuronal activity within the SC during individual saccadic eye movements.
• To compare real-time observations with previous inferences based on averaged neuronal activity.

Main Methods:

• Simultaneous recording of neuronal activity from pairs of neurons along the rostral-caudal axis of the SC in monkeys.
• Analysis of neuronal discharge timing during individual saccades using peak discharge difference, median activation time, and cross-correlation.
• Comparison of neuronal activity onset relative to saccade onset.

Main Results:

• A statistically significant caudal-to-rostral spread of neuronal activation was observed during individual saccades.
• The order of activation was most frequently from caudal to rostral SC neurons.
• Caudal SC activity typically preceded saccade onset, while rostral SC activity occurred during the saccade.

Conclusions:

• Direct evidence supports a caudal-to-rostral spread of activity within the monkey SC during single saccades.
• These findings confirm previous inferences derived from averaged neuronal activity.
• The functional significance of this observed activity spread during saccade generation requires further investigation.